Biosynthetic Pathways of Secondary Metabolites PDF

Biosynthetic pathways of Secondary metabolites INTRODUCTION Metabolism -Metabolism constituents all the chemical transformations occurring in the cells of living organisms and these transformations are essential for life of an organism. Metabolites -End product of metabolic processes and intermedia...

Biosynthetic pathways of Secondary metabolites INTRODUCTION Metabolism -Metabolism constituents all the chemical transformations occurring in the cells of living organisms and these transformations are essential for life of an organism. Metabolites -End product of metabolic processes and intermediates formed during metabolic processes. Primary metabolites : A primary metabolite is a kind of metabolite that is directly involved in normal growth, development, and reproduction. It usually performs a physiological function in the organism (i.e. an intrinsic function). It is also referred to as a central metabolite, which has an even more restricted meaning (present in any autonomously growing cell or organism). Primary metabolites are typically formed during the growth phase as a result of energy metabolism, and are deemed essential for proper growth. Examples of primary metabolites include alcohols such as ethanol, lactic acid, and certain amino acids. Within the field of industrial microbiology, alcohol is one of the most common primary metabolites used for large-scale production. Additionally, primary metabolites such as amino acids including L-glutamate and L- lysine, which are commonly used as supplement which are isolated via the mass production of a specific bacterial species, Corynebacteria glutamicum. Another example of a primary metabolite commonly used in industrial microbiology includes citric acid. Citric acid, produced by Aspergillus niger, is one of the most widely used ingredients in food production. It is commonly used in pharmaceutical and cosmetic industries as well. Secondary metabolite Secondary metabolites are typically organic compounds produced through the modification of primary metabolite synthases. Secondary metabolites do not play a main role in growth, development, and reproduction like primary metabolites do, and are typically formed during the end or near the stationary phase of growth. Many of the identified secondary metabolites have a role in ecological function, including defense mechanism, by serving as antibiotics and by producing pigments. Examples of secondary metabolites with importance in industrial microbiology include atropine and antibiotics such as erythromycin and bacitracin. Atropine, derived from various plants, is a secondary metabolite with important use in the clinic. Atropine is a competitive antagonist for acetylcholine receptors, specifically those of the muscarinic type, which can be used in the treatment of bradycardia. Antibiotics such as erythromycin and bacitracin are also considered to be secondary metabolites. Erythromycin, derived from Saccharopolyspora erythraea, is a commonly used antibiotic with a wide antimicrobial spectrum. It is mass produced and commonly administered orally. Lastly, another example of an antibiotic which is classified as a secondary metabolite is bacitracin. Bacitracin, derived from organisms classified under Bacillus subtilis, is an antibiotic commonly used a topical drug. Photosynthesis Photosynthesis: is the process by which light energy is captured, converted and stored in a simple sugar molecule. This process occurs in chloroplasts and other parts of green organisms. It is a backbone process, in the sense that all life on earth depends on it’s functioning. The following equation sums up the process: 6CO2 (carbon dioxide) + 12 H2O (water) + light energy -> C6H12O6 (glucose) + 6O2 (oxygen) +6H2O (water) Photosynthesis Steps:  During the process of photosynthesis, carbon dioxide enters through the stomata, water is absorbed by the root hairs from the soil and is carried to the leaves through the xylem vessels. Chlorophyll absorbs the light energy from the sun to split water molecules into hydrogen and oxygen.  The hydrogen from water molecules and carbon dioxide absorbed from the air are used in the production of glucose. Furthermore, oxygen is liberated out into the atmosphere through the leaves as a waste product.  Glucose is a source of food for plants that provide energy for growth and development, while the rest is stored in the roots, leaves and fruits, for their later use.  Pigments are other fundamental cellular components of photosynthesis. They are the molecules that impart color and they absorb light at some specific wave length and reflect back the unabsorbed light. All green plants mainly contain chlorophyll a, chlorophyll b and carotenoids which are present in the thylakoids of chloroplasts. It is primarily used to capture light energy. Chlorophyll-a is the main pigment. The process of photosynthesis occurs in two stages:  Light-dependent reaction or light reaction  Light independent reaction or dark reaction Light Reaction of Photosynthesis (or) Light-dependent Reaction  Photosynthesis begins with the light reaction which is carried out only during the day in the presence of sunlight. In plants, the light- dependent reaction takes place in the thylakoid membranes of chloroplasts.  The Grana, membrane-bound sacs like structures present inside the thylakoid functions by gathering light and is called photosystems.  These photosystems have large complexes of pigment and proteins molecules present within the plant cells, which play the primary role during the process of light reactions of photosynthesis.  There are two types of photosystems: photosystem I and photosystem II.  Under the light-dependent reactions, the light energy is converted to ATP and NADPH, which are used in the second phase of photosynthesis.  During the light reactions, ATP and NADPH are generated by two electron-transport chains, water is used and oxygen is produced. The chemical equation in the light reaction of photosynthesis can be reduced to: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP Dark Reaction of Photosynthesis (or) Light-independent Reaction  Dark reaction is also called carbon-fixing reaction.  It is a light-independent process in which sugar molecules are formed from the water and carbon dioxide molecules.  The dark reaction occurs in the stroma of the chloroplast where they utilize the NADPH and ATP products of the light reaction.  Plants capture the carbon dioxide from the atmosphere through stomata and proceed to the Calvin photosynthesis cycle.  In the Calvin cycle, the ATP and NADPH formed during light reaction drive the reaction and convert 6 molecules of carbon dioxide into one sugar molecule or glucose. The chemical equation for the dark reaction can be reduced to: 3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi * G3P – glyceraldehyde-3-phosphate Reactions of the Calvin cycle The Calvin cycle reactions can be divided into three main stages: carbon fixation, reduction, and regeneration of the starting molecule. Carbon fixation. A CO2 molecule combines with a five-carbon acceptor molecule, ribulose-1,5-bisphosphate (RuBP). This step makes a six-carbon compound that splits into two molecules of a three-carbon compound, 3-phosphoglyceric acid (3-PGA). This reaction is catalyzed by the enzyme RuBP carboxylase/oxygenase, or rubisco. Reduction. In the second stage, ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon sugar, glyceraldehyde-3-phosphate (G3P). This stage gets its name because NADPH donates electrons to, or reduces, a three-carbon intermediate to make G3P. Regeneration. Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP and involves a complex network of reactions. Glycolysis Glycolysis: is the metabolic pathway that converts glucose into pyruvate. Occurs in the cytosol and is oxygen-independent. The free energy released during the biochemical reactions in glycolysis is used to generate a net gain of two molecules of ATP. Citric Acid Cycle (Kreb’s cycle) The overall reaction of glucose in terms of ADP and ATP is C6H12O6 + 6CO2 + 38 ADP + 38P (inorganic) → 6H2O + 6CO2 + 38 ATP The Krebs cycle or TCA cycle (tricarboxylic acid cycle) or Citric acid cycle is a series of enzyme catalyzed reactions occurring in the mitochondrial matrix, where acetyl-CoA is oxidized to form carbon dioxide and coenzymes are reduced, which generate ATP in the electron transport chain. It is an eight-step process. Krebs cycle or TCA cycle takes place in the matrix of mitochondria under aerobic condition.  Biosynthetic pathways of Secondary metabolites Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules. This process often consists of metabolic pathways. The building blocks are tiny chemical molecules produced from primary metabolites mostly from photosynthesis, glycolysis, and or Krebs cycle. They are very important in biosynthesis and production of secondary metabolites. These are considered to be intermediates, few important ones are acetyl CoA, shikimic acid , mevalonic acid malonic acid. The building blocks can be segregated based on the number of Carbon units C1 derived from S methyl of L-methionine C2 derived from acetyl –CoA C5 derived from isoprene units C6-C3 units (phenyl propyl units) are derived from phenylalanine or tyrosine through shikimic acid pathway. The Basic Metabolic Pathways Leading To Production of Secondary MetabolitesThrough Photosynthesis Biosynthesis pathway of natural products: 1. Shikimic-acid (shikimate) pathway The shikimic acid pathway (shikimate pathway) is the basic process for biosynthesis of phenolic compounds, alkaloid, and others. It takes place in chloroplast plant cells and have the phenylpropanoid precursors. These aromatic compounds are types of secondary metabolites that abundant in plant, and the expression of them are triggered by environmental stresses, such as pathogens and herbivores attack, inappropriate pH and temperature, UV radiation, saline stress, and heavy metal stress. Shikimic acid pathway is a seven-step metabolic pathway used by bacteria, archaea, fungi, algae, some protozoans, and plants for the biosynthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and tryptophan).The pathway starts with two substrates, phosphoenol pyruvate and erythrose-4-phosphate, and ends with chorismate, a substrate for the three aromatic amino acids. Figure 1: overview of shikimate pathway with the enzymatic process  Figure2.The synthesize process of three aromatic amino acids as protein building blocks produces through shikimate(chorismate) biosynthetic pathway Shikimate biosynthetic pathway is also known as the chorismate pathway. Figure 1 shows the overview of shikimate pathway with the enzymatic process, Phosphoenolpyruvate and erythrose-4-phosphate react to form 3-deoxy-D- arabino- heptulosonate 7-phosphate, in a reaction catalyzed by the enzyme DAHP synthase. The next enzyme involved is shikimate kinase, an enzyme that catalyzes the ATP dependent phosphorylation of shikimate to form shikimate 3-phosphate. Shikimate-3-phosphate is then coupled with phosphoenol pyruvate to give 5- enolpyruvylshikimate-3-phosphate via the enzyme 5-enolpyruvylshikimate-3- phosphate (EPSP) synthase. Then 5-enolpyruvylshikimate-3-phosphate is transformed into chorismate by a chorismate synthase. and the next phase is aromatic amino acid synthesis that produced by shikimate pathway in Figure 2: Tryptophan (L-Trp), Tyrosine (L-Tyr), and Phenylalanine (L- Phe), as molecular building blocks for protein , alkaloids , phenols and other biosynthesis. The shikimate pathway is being a metabolic pathway that connecting central and specialized metabolism in the plant cell and carbon degradation during the synthesis of secondary metabolite compounds. 2. Malonic-acid (Malonate/Acetate) pathway Acetate pathway operates functionally with the involvement of acyl carrier protein (ACP) to yield fatty acylthioesters of ACP. These acyl thioesters forms the important intermediates in fatty acid synthesis. These C2 acetyl CoA units at the later stage produces even number of fatty acids from n-tetranoic (butyric) to n-ecosanoic (arachidic acid). In fatty acid synthesis, acetyl‐CoA is the direct precursor only of the methyl end of the growing fatty acid chain. All the other carbons come from the acetyl group of acetyl‐ CoA but only after it is modified to provide the actual substrate for fatty acid synthase. Malonyl‐CoA contains a 3‐carbondicarboxylic acid, malonate, bound to Coenzyme A. Malonate is formed from acetyl‐CoA by the addition of CO2 using the biotin cofactor of the enzyme acetyl‐CoA carboxylase. Figure 3. The acetate –malonate pathway for biosynthesis of fatty acids 3. Mevalonic-acid (Mevalonate) pathway The mevalonic acid (MVA) pathway or mevalonate pathway also known as the isoprenoid pathway that involves the synthesis of 3-hydroxy-3- methylglutaryl-CoA reductase (HMGCR). Moreover, the MVA pathway is the core of metabolic pathway for multiple cellular metabolisms in eukaryotic, archaea, and some bacteria organisms, including cholesterol biosynthesis and protein. Cholesterol is produced as the molecules that used to build the membrane cell structure, steroid hormones, myelin sheets in neuron system, precursors of vitamin D, formation and release of synaptic vesicles. Mevalonic acid further produced isopentenyl pyrophosphate (IPP) and its isomer dimethylallyl pyrophosphate (DMAPP). These two main intermediates IPP and DMAPP set the ‘active isoprene’ unit as a basic building block of isoprenoid compounds. Both of these units yield geranyl pyrophosphate (C10-monoterpenes) which further association with IPP produces farnesyl pyrophosphate (C15-sesquiterpenes). Farnesyl pyrophosphate with one more unit of IPP develops into geranyl-geranyl pyrophosphate (C20-diterpenes). The farnesyl pyrophosphate multiplies with its own unit to produce squalene, and its subsequent cyclization gives rise to cholesterols and other groups like triterpenoids. Figure4.Mevalonate(MVA)pathway.  Vitamins Dr: Aseel M. Omran Introduction Vitamins are organic substances, not synthesized within the body, that are essential in small amounts for the maintenance of normal metabolic functions. They do not furnish energy and are not utilized as building units for cellular structure. The lack of specific vitamins leads to distinctive deficiency states such as beriberi, rickets, scurvy, and xerophthalmia, or to conditions without definitive symptoms. The term vitamin was derived in 1911 when an amine thought to prevent beriberi was isolated from rice bran; this essential or vital amine was called a vitamin. Not all vitamins are amines; vitamins A, C, D, E, K, and inositol lack a nitrogen function of any type. The vitamins are diverse chemically, ranging from a simple molecule such as niacin to a complex molecule such as cyanocobalamin. Vitamins are distributed widely and are normally ingested as constituents of various food substances. Fresh fruits, leafy vegetables, whole grains, eggs, and liver are rich dietary sources of vitamins. Vitamins obtained from natural sources and those prepared synthetically are in distinguishable biochemically, nutritionally, and therapeutically. Vitamins may be used as special dietary supplements or as drugs. Vitamin supplements are technically foods for special dietary needs and are unnecessary in most cases in which there is a balanced diet. Vitamins are considered drugs if they are taken to treat a condition of vitamin deficiency or to prevent imminent development of a disease. Vitamins can be classified into two classes: 1. fat soluble vitamin (A, D, E, K). 2. water soluble vitamins (C, B complex). Storage of vitamins: The fat soluble vitamins :- are stored in the body and their deficiencies are relatively rare. On the other hand, excessive intakes may be toxic. The water soluble vitamins :- are not stored to any significant extent in the body. Excess supplements of these vitamins are usually excreted in the urine. FAT-SOLUBLE VITAMINS Vitamins A, D. E, and K are fat soluble. Their absorption from the intestinal tract is associated with that of lipids, and a deficiency state may be caused by conditions that impair fat absorption. These conditions include pathologic situations such as biliary cirrhosis, cholecystitis, and sprue, and therapeutic situations such as cholestyramine regimens and excessive use of mineral oil laxatives. Vitamin A (Retinol) Vitamin A is a term applied to all derivatives of β -ionone, other than the carotenoids, Retinol is the major natural form of the vitamin, but known forms include the acetate and palmitate esters of the alcohol. Retinol is readily absorbed (80 to 90%) from the normal intestinal tract and is stored in body tissues, especially the liver. An estimated one third of the ingested vitamin A is stored under normal circumstances. Sources: - Fish liver oils are the natural sources of the vitamin and formerly were its primary commercial sources. - Common dietary sources of vitamin A are animal organs (heart, kidney, liver) - Vitamin A activity is also derived from some plant carotenoids that occur in carrots and green leafy vegetables. Only carotenoids that possess at least one unhydroxylated β -ionone ring (α-, β -, and -y-carotene and cryptoxanthin) can be converted to vitamin A. Beta-carotene and related carotenoids (provitamin A substances) are cleaved by β -carotene oxygenase in mucosal cells of the intestine to yield retinal, most of which is promptly reduced in the presence NADH to retinol. Uses of Vitamin A : 1.Vision 2.growth and development 3.Immune function 4. Red blood cell formation 5.Skin and bone formation. 6. Regulating gene transcription A deficiency of this vitamin can result in a variety of conditions including nyctalopia (night blindness), xerophthalmia, hyperkeratosis of the skin, growth retardation, and decreased resistance to infection. Xerophthalmia Nyctalopia hyperkeratosis Vitamin D  Vitamin D2 (ergocalciferol)  Vitamin D3 (cholecalciferol) Vitamin D is a term that is used for several related steroids and their metabolites that are essential for the absorption and utilization of calcium. The two forms of vitamin D differ depending on their food sources. Vitamin D3 is only found in animal-sourced foods, whereas D2 mainly comes from plant sources and fortified foods. Sources of Vitamin D3  Oily fish and fish oil  Liver  Egg yolk  Butter  Dietary supplements Sources of Vitamin D2  Mushrooms (grown in UV light)  Fortified foods  Dietary supplements Vitamin D has been called the sunshine vitamin since ultraviolet light is involved in the conversion of provitamin substances to vitamins D2 and D3. Vitamin D3 Is Formed in Your Skin Your skin makes vitamin D3 when it’s exposed to sunlight. Specifically, ultraviolet B (UVB) radiation from sunlight triggers the formation of vitamin D3 from the compound 7-dehydrocholesterol in skin. A similar process takes place in plants and mushrooms, where UVB light leads to the formation of vitamin D2 from ergosterol, a compound found in plant oils. If you regularly spend time outdoors, lightly clad and without sunscreen, you may be getting all the vitamin D you need. Uses of vitamin D :- 1.In the intestine assists in the absorption of calcium and phosphorus. 2.playing a role in bone and calcium homeostasis 3.Maintains muscle and nerve contraction 4.important for immune system function. 5.Maintains general cellular function in all cells of the body 6.use in cardiovascular disease, cancer , diabetes and multiple sclerosis. Deficiency states lead to rickets in children and osteomalacia in adults. Vitamin E (tocopherol) Vitamin E is a term that refers to various forms of α-tocopherol. Several structurally related tocopherol analogs also occur in nature, including B, y-, and S-tocopherols, but these substances possess only low levels of vitamin E activity. - Vitamin E is widely distributed in nature, and the body's requirements are normally satisfied by dietary sources. Dietary sources Plant oils, green vegetables, whole grains, egg yolks, and meats are common dietary sources of this vitamin. Wheat germ oil is a traditional natural source of vitamin E for therapeutic purposes. Uses of vitamin E Vitamin E is the major lipid-soluble antioxidant protects cell membranes, proteins, and DNA from oxidation and thereby contributes to cellular health. It prevents oxidation of the polyunsaturated fatty acids and lipids in the cells.  formation of blood vessels boosting of immune function Vitamin E deficiency can cause nerve and muscle damage that results in loss of feeling in the arms and legs, loss of body movement control, muscle weakness, and vision problems. Another sign of deficiency is a weakened immune system Vitamin K (naphthoquinone) Vitamin K1 (phytonadione, phylloquinone) Vitamin K2 (menaquinone) Vitamin K3 (Menadione) Vitamin K4 (Menadiol) Vitamin K is a term that refers to 2- methyl-1,4-naphthoquinone and derivatives of this compound. Sources: Vitamin K is distributed widely in dairy products and many fruits and vegetables, green leafy vegetables being especially good dietary sources. The intestinal microflora also provide a significant portion of the normal human supply of this vitamin. Uses of vitamin K Vitamin K acts primarily in blood clotting (antihemorrhagic activity) treatments for bleeding events caused by overdose of the anticoagulant drug warfarin  Helps in metabolism of bone proteins (osteocalcin) without vitamin K, osteocalcin cannot bind to the minerals that normally form bones, resulting in poor bone mineralization. regulation of blood calcium levels. deficiency : Hemorrhageis the most common symptom in vitamin K deficiency  WATER-SOLUBLE VITAMINS B-complex Vitamins Vitamin B1 Thiamine or vitamin B1 has subs tuted pyrimidine and thiazole rings linked by a methylene bridge. Final steps in both the biosynthesis and chemical synthesis of this vitamin involve linkage of the two ring systems. Commercial supplies of thiamine are prepared by chemical synthesis, and it is usually used as the hydrochloride salt. The vitamin is stable in an acidic environment but decomposes readily above pH 5.0. It is es mated that about 50% of the vitamin in foods is destroyed during cooking. ti ti  Source: Whole grains, legumes, and meats are good dietary sources of thiamine. Although the substance is absorbed readily from the small intes ne, alcohol inhibits its absorp on. Uses of Vitamin B1 1. Thiamin is a sulfur-containing vitamin that par cipates in energy metabolism 2. conver ng carbohydrates, lipids and proteins into energy. 3. plays a key role in nerve and muscle ac vity. 4. Thiamin may be helpful to people with Alzheimer disease. 5.Development of myelin sheaths and improves brain func on Vitamin B1 (thiamine) de ciency cause of several clinical syndromes, including Wernicke, encephalopathy, beriberi. Risk factors include alcohol dependence, malabsorp on, and a diet low in thiamine (e.g., based on polished rice).  ti ti ti fi ti ti ti ti  Beri beri Vitamin B2 Ribo avin or vitamin B 2 is a yellow, heat-stable substance that is slightly soluble in water. It is sensi ve to light and will change into lumichrome or lumi avin, depending on whether the irradiated solu on is acidic or alkaline; neither lumichrome nor lumi avin possesses physiologic ac vity.  fl fl ti fl ti ti  Sources: Yeast is the richest natural source of ribo avin. Dairy products, eggs, legumes, and meats are the main dietary sources of this vitamin. Small amounts are provided by cereal grains, fruits, and green vegetables. Ribo avin is stable during cooking in the absence of light. Ribo avin occurs in foods in the free form and as ribo avin 5'- phosphate (Flavin mononucleo de or FMN) and avin adenine dinucleo de (FAD). The nucleo des are hydrolyzed to ribo avin in the upper gastrointes nal tract. Free ribo avin is absorbed readily into cells of the intes nal mucosa by an ac ve transport system that is enhanced by bile salt. Uses of Vitamin B2 1. Coenzyme func ons in numerous oxida on-reduc on reac ons which are necessary for releasing energy from carbohydrates, fats and proteins. 2. s mulates growth and reproduc on 3. plays a role in vision 4. plays a role in conversion of vitamins B6, folic acid, and niacin into their ac ve coenzyme forms. 5. neutralizes free radicals hence acts as an -oxidant De ciency causes stoma s and derma s ti fi ti fl ti ti ti ti ti ti ti ti ti ti ti ti fl fl ti ti fl fl ti ti fl fl  vitamin B3 Niacin, nico nic acid, or vitamin B3 is a simple, naturally occurring pyridine deriva ve that prevents pellagra. Niacinamide or nico namide also occurs naturally, has an pellagra ac vity, and is used for dietary and therapeu c purposes. They are readily absorbed from the gastrointes nal tract under normal circumstances. Sources meats, sh, and dairy products are good dietary sources of niacin. The roas ng of co ee beans results in the release of signi cant quan ty of niacin as well as in the development of a characteris c avor. Tryptophan is also converted to niacin in the body. Uses of Vitamin B3 1. Niacin acts as coenzyme in energy-transfer reac ons 2. Niacin is similar to the ribo avin coenzymes in that it carries hydrogen during metabolic reac ons. ti fi ti ti ti ti ti ti fl ff ti fl ti ti ti ti fi  3. protects against neurological degenera on and Alzheimer’s disease 4. Helps lower LDL cholesterol 5. lowers risk of cardiovascular diseases and eases arthri s. De ciency Pellagra is the classic niacin-de ciency condi on. Symptoms of the de ciency involve the nervous system, the skin, and the gastrointes nal tract and are some mes summarized as the 3D's—demen a, derma s, and diarrhea. Oral lesions, especially angular stoma s, , and red tongue, are more dis nc ve than the other symptoms. Vitamin B5 Pantothenic acid or vitamin B5 is a component of the vitamin B complex that is some mes known as the "chick an derma s factor" (based on a prior bioassay procedure). Pantothenic acid is a naturally occurring compound that on hydrolysis yields B-alanine and pantoic acid, a subs tuted butyric acid deriva ve. Sources: Animal organs (heart, kidney, and liver) and cereal grains are rich dietary sources of pantothenic acid. fi fi ti ti ti ti ti ti fi ti ti ti ti ti ti ti ti ti ti ti ti  Uses of vitamin B5 1. turn the food into the energy 2.involved in the synthesis of lipids, neurotransmi ers, steroid hormones, and hemoglobin. 3.maintenance and repair of ssues and cells of the skin and hair 4.helps in healing of wounds and lesions 5.normalizes blood lipid pro le De ciency causes fa gue and sleep disturbances Vitamin B6 Vitamin B6 is a term that is applied to pyridoxol, pyridoxal, and pyridoxamine, three closely related, naturally occurring, highly subs tuted pyridine deriva ves with comparable physiologic ac vity. Pyridoxine is the term that is usually used for pyridoxol in pharmacy and medicine. This alcohol is the predominant form of the vitamin in plant materials. Pyridoxal and pyridoxamine occur in animal ssues. Because pyridoxine is the most stable of these substances, synthe cally prepared pyridoxine is the material usually used for exogenous dietary supplementa on and therapeu c purposes. ti fi ti ti ti ti fi ti tt ti ti ti  Sources: Beef liver. Tuna. Salmon. For ed cereals. Chickpeas, Poultry. Some vegetables and fruits, especially dark leafy greens, ananas, papayas, oranges, and cantaloupe. Uses of vitamin B6 1. Improve Mood 2. Vitamin B6 is required for biological reac ons (amino acid metabolism, neurotransmi er synthesis, red blood cell forma on). 3. Acts as a cri cal co-factor for a diverse range of biochemical reac ons that regulate basic cellular metabolism. De ciency causes peripheral neuropathy Symptoms of vitamin B de ciency somewhat resemble those of niacin and ribo avin de ciencies. They include neurology abnormali es, skin lesions, and hypochromic microcy c anemia. Vitamin B7 Source: Foods that contain the most bio n include eggs, sh, meat, seeds, nuts, and certain vegetables (such as sweet potatoes) fi fl ti tt fi fi ti fi ti ti ti ti fi ti ti  Uses of Vitamin B7 1. Bio n plays an important role in metabolism as a coenzyme that transfers carbon dioxide. 2. This role is cri cal in the breakdown of food (carbohydrates, fats and proteins) into energy. 3. Bio n is involved in many cellular reac ons, par cularly in fat and protein metabolism of hair roots, nger nails, and skin. 4. Used in fa y acid synthesis De ciency causes Fa gue, depression and derma s Vitamin B9 Folic acid, folacin, pteroylglutamic acid, and occasionally vitamin B 9 are terms that refer to a material with an anemia proper es  ti ti fi tt ti ti fi ti ti ti ti ti ti  sources: Beans. Peanuts. Sun ower seeds. Fresh fruits, fruit juices. Whole grains. Liver. Uses of Vitamin B9 1. Folate is essen al for brain development and func on. 2. It aids in the produc on of DNA and RNA 3.metabolism of vitamins and amino acids 4. The nutrient is crucial during early pregnancy to reduce the risk of birth defects of the brain and spine 5.Required for synthesis of glycine, methionine, nucleo des T & U De ciency state include megaloblas c and macrocy c anemias and glossi s. Vitamin B12 Vitamin B12 (cobalamins) are terms that refer to a series of porphyrin- related corrinoid deriva ves that func on as extrinsic factors to prevent pernicious anemia. Cyanocobalamin, a red crystalline material, is the most stable of the cobalamins; consequently, it is the form of vitamin B12 most frequently u lized in therapy. Hydroxocobalamin also nds some therapeu c use; in it the cyano group is replaced with a hydroxyl subs tuent. fi ti ti ti ti ti fl ti ti ti ti ti ti ti fi  Uses of vitamin B12 1. act as a coenzyme in the conversion of homocysteine to methionine, 2. play role in the metabolism of fa y acids and amino acids 3.produc on of neurotransmi ers. 4. maintains a special lining that surrounds and protects nerve bers 5. bone cell ac vity depends on vitamin B12. 6. Plays a signi cant role in DNA synthesis 7. It helps in brain func on and synthesis of red blood cells de ciency usually involve rapidly dividing cells of the hematopoie c system (e.g.,megaloblas c anemia) and irreversible neurologic damage (e.g., defec ve myelin nerve sheaths); they include irritability, weakness, memory loss, mood swings, and a sensa on of ngling or numbness of the arms and legs.  fi ti ti ti fi ti ti tt tt ti ti fi ti  Vitamin C Vitamin C or L-ascorbic acid is a naturally occurring vitamin substance that pre vents scurvy and has useful an oxidant proper es. It occurs in equilibrium with dehydro-L-ascorbic acid, an oxidized form, which also has an scorbu c proper es. Vitamin C is the least stable of all the vitamins. Sources: Good dietary sources of ascorbic acid include citrus fruits, tomatoes, strawberries, and other fresh fruits and vegetables. Although the vitamin content is preserved on freezing, up to 50% of the vitamin C content is lost upon cooking. Uses of vitamin C 1. One of the important proper es is an oxidant ac vity. 2. func ons in enzyme ac va on and oxida ve stress reduc on 3. play roles in the synthesis of collagen and absorp on of iron ti ti ti ti ti ti ti ti ti ti ti ti ti ti  4. defense against infec ons and in amma on 5. helps to prevent certain diseases such as cancer, common cold, cardiovascular diseases and cataract. Vitamin C de ciency causes scurvy fi ti fl ti Glycosides Glycoside: is an organic compound, usually of plant origin, that is composed of a sugar portion linked to a non-sugar moiety by glycosidic bond. The sugar portion is called glycon, The non-sugar portion is called aglycon or genin; In general there are four basic classes of glycosides:C- glycosides, in which the sugar is attached to the aglycone through C-C bond, and the O- glycosides in which the sugar is connected to the aglycone through oxygen –carbon bond,S-glycosides and N-glycosides.  therefore glycosides yield one or more sugars among the products upon enzymatic or acid hydrolysis. The sugar component of glycosides may be mono, di, tri or tetrasaccharides.  Alpha and Beta glycosides Sugars in glycosides exist in isomeric α and β forms so both α and β glycosides are theoretically possible. but the β-form is the one that occur in plants The two diastereoisomers differ in configuration about the anomeric carbon (C-1) can exist α and β. If the hydroxyl group on the anomeric carbon is down in relation to the cyclic structure, it is α anomer while if the hydroxyl group on the anomeric carbon is up in relation to the cyclic structure, it is β anomer.  Chemically the glycosides are acetals in which the hydroxyl group (OH) of the glycone is condensed with the hydroxyl group of aglycone. Sugars exist predominantly as cyclic hemiacetals (R-O-C-OH group), while glycosides are usually mixed acetals (R-O-C-O-R) group.  Inside the body the glycosides will be cleaved to glycone and aglycone parts, the glycone part confers on the molecule solubility properties, thus is important in the absorption and distribution in the body, while the aglycone part is responsible for the pharmacological activity. Physical and chemical properties of glycosides Because of the complexity of the structure of the naturally occurring glycosides, no generalization are possible with regard to their stability. In addition there are differences in their solubility properties.  1. Solubility: Most glycosides are soluble in water or hydroalcoholic solutions and insoluble or less soluble in non-polar organic solvents, because the solubility properties of the sugar residues exert a considerable effect i.e. sugar moiety increases water solubility. The aglycon part is soluble in non-polar (organic) solvents like benzene, ether and chloroform.  2. Stability and hydrolytic cleavage: A. Acids and alkali: Glycosides can be hydrolyzed by heating with a dilute acid where by the glycosidic linkages are cleaved, while glycosides are relatively stable towards alkalis. Glycosides can be hydrolyzed by heating with a dilute acid where by the glycosidic linkages are cleaved. Glycosides can be also hydrolyzed by appropriate enzymes, which are usually found in the same plant, in separate compartments. There is a specific enzyme for each glycosides to exert a hydrolytic action on it.  B. Enzyme hydrolysis: Enzymatic hydrolysis: there is a specific enzyme that exerts a hydrolytic action on it. Glycosides can be hydrolyzed by appropriate enzymes, which are usually found in the same plant, in separate compartments. The same enzyme is capable to hydrolyze different glycosides, but α and β stereo-isomers of the same glycoside are usually not hydrolyzed by the same enzyme. Emulsin is found to hydrolyzed most β-glycoside linkages while maltase and invertase are α-glycosidases, capable of hydrolyzing 3. Shape, color, taste and odor A. Shape: Glycosides are solid, amorphous and non volatile. B. Color: Glycosides are colourless except flavonoids are yellow and anthraquinones are red or orange. C. Taste: Most of glycosides are bitter taste. D. Odor: Glycosides are odorless except saponin (glycyrrhizin) Importance of Glycosides 1. Glycosides play an important role in the life of the plant and are involved in different functions. It serve as: A. As sugar reserves B. As waste products of plant metabolism C. As a mean of detoxification D. To regulate osmosis E. To regulate the supply of substances of importance in metabolism F. Has a role of defense against the invasion to the tissues by microorganism some pointed out that aglycones are antiseptics and hence are bactericidal in nature  2. Many therapeutic agents are derived from glycosides. In fact, the group contributes to almost every therapeutic class. A. Some of our most valuable cardiac glycosides from digitalis, strophanthus, squill and others. B. Laxative drugs, such as senna, aloe, rhubarb, cascara sagrada, and frangula, contain emodin and other anthraquinone glycosides; C. Sinigrin, a glycoside from black mustard, yields allyl isothiocyanate, a powerful local irritant. Classification of glycosides 1- According to the type of glycosidic linkage: α-glycosides (α sugar) β-glycosides (β sugar) 2- according to the chemical group of the aglycon involved in the formation of glycoside linkage. Aglycone- O- Sugar O-glycosides(OH group): eg. Senna and rhubarb Aglycone- C- Sugar C-glycosides (C- group): eg. Cascaroside from cascara Aglycone- S- Sugar S-glycosides (SH- group): eg. sinigrin from black mustard Aglycone-N-Sugar: N-glycosides(NH-group): eg. glycoalkaloid. 3- According to the chemical nature of the aglycon, the glycosides containing drugs can be classified into: Cardioactive group. Anthraquinone group. Saponin group. Cyanophore group. Isothiocyanate group. Flavonol group. Alcohol group. Aldehyde group. Phenol group 4- According to the nature of the simple sugar component of the glycoside: 1- Glucoside (the glycone is glucose). 2- Galactoside (the glycone is galactose). 3- Mannoside (the glycone is mannose). 4- Arabinoside (the glycone is arabinose). Biosynthesis of glycosides The biosynthetic pathways are widely variable depending on the type of aglycone as well as the glycone units. The aglycone and the sugar parts are biosynthesized separately, and then coupled to form a glycoside. The coupling of the two parts occurs via phosphorylation of a sugar to yields a sugar 1- phosphate which reacts with a uridine triphosphate to form a uridine diphosphate sugar (UDP-sugar) and inorganic phosphate. This UDP-sugar reacts with the aglycone to form the glycoside and a free UDP sugar phosphorylation sugar-1-P UTP + sugar-1-P UDP – sugar + Ppi UDP – sugar + aglycone sugar – aglycone + UDP (glycoside) Extraction of glycosides Since glycosides are accompanied by specific hydrolyzing enzymes, these enzymes must be inactivated by putting the plant in boiling water or alcohol. Defatting or purification of the plant material in case of seeds. 1. Defatting or purification of the plant material in case of seeds. 2. Treatment with lead acetate to precipitate tannins and other non glycosidal impurities. 3. Removal of any excess of lead acetate by passing hydrogen sulfide H2S gas through the solution. 4. The extract is filtered and concentrated to get crude glycoside. 5. Purification of the crude glycosides by chromatography or crystallization. Cardioactive glycosides By Dr. ENASS NAJEM  Cardioactive glycosides The glycosides of this group are characterized by their highly specific action on cardiac muscle, increasing tone, excitability and contractility. The aglycones of these glycosides are referred to as "cardiac genin". They are steroidal in nature, specifically, they are derivatives of cyclopentaphenanthrene containing an unsaturated lactone ring attached to C17.  Structure Of Glycosides Two types of genin may be distinguished according to whether there is a five-or six-membered lactone ring. These types are known respectively as cardenolides (e.g. digitoxigenin) and bufanolides or bufadienolides (e.g. scillarenin). The following formulae indicate their structure and ring numbering: 1- the cardenolide. In the cardenolide (aglycones with 23 carbons), the lactone ring attached at C17 is a butenolide (4 carbons), which is also referred as α,β- unsaturated lactone ring. E.g. the glycosides of digitalis and strophanthus species  Cardenolide (c23) Digitalis glycosides R=CH3 Strophanthus glycosides R=CHO OR CH2OH 2- the scilladienolide (which are referred to as bufadienolide). In the scilladienolide (aglycone with 24 carbons), the lactone ring attached at C17 is a pentadienolide (5 carbons with two double bonds) which is also called a pentenolide. These two types of lactone rings give different reactions to certain color tests. the squill glycosides and, Bufotoxin.  Bufadienolides Squill glycosides R1=OH, R2=H Bufotoxin R1 & R2 = ester group The glycone portion at position C-3 of cardiac glycosides may contain four monosaccharide molecules linked in series. Thus, from a single genin one may have a monoside, a bioside, a trioside or a tetroside. All cardioactive glycosides are characterized by the following structural features 1. The presence of β-OH at position C-3, which is always involved in a glycosidic linkage to a mono, di, tri, OR tetra saccharide. 2. The presence of another β-OH group at C-14. 3. The presence of unsaturated 5 or 6- membered lactone ring at position C-17, also in the β configuration. 4. Additional OH groups may be present at C-5, C-11 and C-16. Nomenclature of cardioactive glycosides The sequence of nomenclatureis as follows: 1- arrange the functional groups and denote their configuration. 2- denote 5 whether α or β. 3- denote the type of glycoside. 4- denote the position of the double bonds. Example: O 3 β hydroxyl- 11-oxo- 5α-card-6,15,20 -trienolide If the compound has one double bond then it is called cardenolide, if has two double bonds then it's called dienolide, but if it has no double bond then it is called cardanolide and bufanolide. Biosynthesis of cardioactive glycosides: Most of the knowledge of the biosynthesis of steroids has been derived from studies of cholesterol production. Aglycones of the cardiac glycosides are derived from mevalonic acid but the final molecules arise from a condensation of a C21 steroid with a C2 unit (the source of C-22 and C-23). Bufadienolides are condensation products of a C21 steroid and a C3 unit Drugs containing cardioactive glycosides 1- Digitalis or foxglove It’s the dried leaf of Digitalis purpurea; F: Scrophulariaceae. Digitalis is from the latin digitus, meaning finger and refers to the finger shaped corolla, purpurea is latin and refer to the purple color of the flower. Constituents The drug contain a large number of glycosides of which the most important from the medicinal view point are: Digitoxin, gitoxin and gitaloxin. The average concentration is about 0.16%. Nearly 30 other glycosides have been identified in the drug e.g. purpurea glycosides A, purpurea glycoside B, gluco-gitaloxin, gluco-digitoxigenin. Primay glycosides with acetylated sugar moieties Digitalis lanata Nearly 70 different glycosides have been detected in the leaves of Digitalis lanata. All are derivatives of five different aglycones, three of which (digitoxigenin, gitoxigenin and gitaloxigenin) also occur in Digitalis purpurea. The other two types of glycosides are derived from digoxigenin and diginatigenin occur in Digitalis lanata but not in digitalis purpurea. the leaves of which are used as a source of the glycosides digoxin and lanatoside C  Lantoside A ,B and E are acetyl derivatives of purpurea A,B and E respectively. Glycosides derived from Digitoxigenin: a- Lanatoside A = Digitoxigenin---DX---DX----DX(AC)---G. b- Acetyl-digitoxin = Digitoxigenin---DX---DX----DX---(AC). c- Digitoxin = Digitoxigenin------DX---DX----DX. d- Purpurea gly A = Digitoxigenin---DX---DX----DX---G DX = Digitoxose, DX (AC)=Acetyldigitoxose,G = Glucose. Mechanism of action It act through inhibition of Na+/K+ ATPase enzyme (membrane bound enzyme). This enzyme keep K+ inside the cell and Na+ outside the cell; so when this enzyme is inhibited K+ transport back into the cell is blocked and its concentration in the extracellular fluid increases, at the same time Na ions will enter the cell and this will promote or facilitate the entry of Ca +2 which are essential for the contraction of actin and myosine. Therefore these agents used in the treatment of congestive heart failure. 2- Strophanthus Is the dried ripe seeds of strophanthus kombe or strophanthus hispidus F: Apocyanaceae. The principal glycosides are K- strophanthoside, K-strophanthin-B and cymarin, all based on the genin strophanthidin Constituents: k-strophanthoside, also known as strophoside. Is the main glycoside in both S.kombe and S.hispidus. it is composed of the genin strophanthidin coupled to a trisaccharide consisting of cymarose, β-glucose and α- glucose. Strophanthin is used I.V. as a cardiotonic. Ouabin (G-strophanthin) It is obtained from S.grantus (F: apocynaceae) Uses: it is a most polar cardioactive glycosides Act as a cardiotonic. i.v. for prompt therapeutic effect. It is absorbed so slowly and irregularly from the alimentary canal that the oral administration is not recommended and is even considered unsafe.  Ouabin (G-strophanthin) (ouabagenin, the sugar is rhamnose) Ouabagenin differs from K-strophanthidin in having 2 additional (OH) groups at C-1 and C-11 and having a alcoholic group at C- 10 instead of the aldehydic group. 3- Oleander Is another plant that contains cardiac glycosides. The leaves of Nerium oleander ( F: Apocyanaceae) have been used to treat cardiac insufficiency. The main constituent is oleanderin (is a promising agent for anticancer treatment). Oleander has historically been considered a poisonous plant because some of its compounds may exhibit toxicity, especially to animals, when consumed in large amounts. sugar Oleanderin 4-(bufadienolide) squill bulb of the white variety of Urginea maritima known as white or Mediterranean squill, or of Urginea indica known in commerce as indian squill, F: liliaceae. The genins of squill glycosides differ from those of the cardenolides in two important aspects: 1- They have six membered doubly unsaturated lactone ring in position C-17. 2- They have at least one double bond in the steroid nucleus. Uses: as an expectorant but it also possesses emetic, cardiotonic and diuretic properties. Red squill consists of the bulb of the red variety of Urginea maritima, which is mostly used as rat poison