Plants Secondary Metabolites

PLANTS SECONDARY METABOLITES By Dr. Sheeba Naz  INTRODUCTION  Plants produce a variety of compounds that can be divided into primary metabolites and secondary metabolites.  Primary Metabolites:  Compounds that are essential for the survival of the plant (...

PLANTS SECONDARY METABOLITES By Dr. Sheeba Naz  INTRODUCTION  Plants produce a variety of compounds that can be divided into primary metabolites and secondary metabolites.  Primary Metabolites:  Compounds that are essential for the survival of the plant (sugars, proteins and amino acids).  Secondary Metabolites:  Produced in other metabolic pathways are not essential to the plant’s growth, but the plants suffer without them.  Secondary metabolites have many uses.  Some are beneficial, and others can be toxic PRIMARY METABOLITES  Molecules that are essential for growth and development of an organism.  Examples:  1.Carbohydrates  2.Proteins  3. Lipids  4.Vitamins  5. Nucleic acid components SECONDARY METABOLITES  Organic compounds /phytochemicals: not directly involved in the normal growth, development or reproduction of the plant.  Classified: Terpenes, Phenolic compounds and Nitrogen containing compounds.  Biosynthesis: derived from primary metabolism pathways  Extracted: from plants using organic solvents and modern separation techniques for isolation.  Economic importance: antimicrobial, pharmaceuticals, plant defense against herbivores, fragrance, stimulants, toxicity, attractant, plant breeding, physiological stress response, and allelopathtic effect.  Possibly over 250,000 secondary metabolites in plants  Classified based on common biosynthetic pathways where a chemical is derived.  Four major classes:  Alkaloids  Terpenoids  Phenolics  Glycosides ALKALOIDS  Alkaloids are secondary metabolites.  Low molecular weight  Primarily composed of nitrogen  Compounds have a ring structure and a nitrogen residue.  Most are derived from amino acids  (i.e., tyrosine, tryptophan, ornithine or argenine, and lysine).  Widely used in medicine  Indole alkaloids is the largest group in this family, derived from tryptophan  Applied to basic nitrogenous compounds of plant origin that are physiologically active.  Organic nitrogenous compounds with a limited distribution in native nature. NITROGEN CONTAINING COMPOUNDS!  Alkaloids  important pharmacological properties:  further classified into many groups - Pyridine alkaloids , e.g. nicotine - pyrrolidine alkaloids , e.g. stachydrine - piperidine alkaloids , e.g. coniine - tropane alkaloids , e.g. atropine - quinoline alkaloids , e.g. quinine - Isoquinoline alkaloids , e.g. berberine - Quinolizidine alkaloids , e.g. lupinine - Indol alkaloids , e.g. resprine CHARACTERISTICS  Bitter in taste.  Derived from amino acids that are most often serve as alkaloidal precursors  (Phenylalanine, tyrosine, tryptophan, histidine, anthranilic acid, lysine and ornithine).  Insoluble or sparingly soluble in water, but the salts formed on reaction with acids are usually freely soluble.  Most are crystalline solids although a few are amorphous.  Free alkaloids are usually soluble in polar solvents like ether, chloroform  Some alkaloids are liquid because of lack of oxygen in their molecules.  (e.g. coniine, nicotine, spartenine) SOURCES AND OCCURRENCE OF ALKALOIDS  Alkaloids can occur in plant kingdoms; among the angiosperms  Leguminosae  Papaveraceae  Ranunculaceae  Rubiaceae  Solanaceae  Berberidaceae are outstanding alkaloid-yielding plants USES OF ALKALOIDS IN PLANTS  Poisonous agents which protect plants against insects and herbivores.  For regulatory growth factors  Reserve substance capable of supplying nitrogen or other elements necessary to the plant’s economy NAMING FOR ALKALOIDS  From the generic name or the genus of the plant yielding them (e.g. vinblastine and vincristine. atropine).  The specific name or species of the plant yielding alkaloids ( e.g belladonnine).  All names of alkaloids should end in “-ine”. ~ A prefix or suffix is added to the name of a principal alkaloid from the same source. (quinine, quinidine, hydroquinine) PHARMACOLOGIC ACTION OF ALKALOIDS  Analgesic (morphine, codeine)  Narcotics (strychnine, brucine which are central stimulant)  Anti malarial ( quinine)  Anti pyretic (fever)  Anti cancer (vincristine)  Mydriatics (atropine) Eye problems  Anti inflammatory  Ephedrine (rises in blood pressure, bronchodilator)  Reserpine (produce fall in excessive hypertension) USES  Antimalarial  It has a skeletal muscle relaxant effect.  It is widely used for the prevention and treatment of nocturnal recumbency (leg cramps)  Vincristine- (Anti-cancer)  Vinca alkaloids- The Vinca alkaloids are a subset of drugs that are derived from the periwinkle plant, catharanthus roseus.  Serpentine- Isolated from rauwolfia serpentina  Treat high blood pressure  treat insect stings and the bites of venomous reptiles  The known alkaloid is caffeine.  It has protective properties for the plants it comes from: cocoa, coffee and tea.  TERPENOIDS Isoprene C5 is the basic unit of the terpenoids Production in Plants: * Flowers  * Leaves  * Fruit Biological Role (volatile and non-volatile):  -Flavour, fragrance, scent  -Antibiotics  -Hormones  -Membrane lipids  -Insect attractants  -Insect antifeedants TERPENES  Terpenoids are made of isoprene units and are found in all plants.  They are the largest group of secondary metabolites and are very volatile, which means they evaporate easily.  Isoprene: to protect the plant from heat.  Essential oils give plants their fragrance.  In some plants, to deter herbivores and protect the plant from dangerous pathogens.  Use essential oils for aromatherapy and medicine.  In aromatherapy, essential oils are used to improve the mood and mental functioning.  In alternative medicine, essential oils have more benefits.  Used for skin issues, respiratory ailments and as antiseptics.  Taxol, which has become important in the medical field.  It is used to treat ovarian and breast cancer.  Taxol comes from the bark of the Pacific yew tree.  Other sources of taxol include a fungus that grows on the tree and needles of the European yew.  The final type of terpenoid is the one that is the most familiar to us: rubber.  It is the largest of the terpenoids because it contains over 400 isoprene units.  Rubber is obtained from latex, which is a fluid produced by Hevea brasilenis.  Use rubber in shoes, erasers, tires, gloves. CLASSIFICATION OF TERPENES  Type of Number of Isoprene Terpene Carbon Atoms Units  Hemiterpene, sesquiterpene, diterpene, triterpene, tetraterpene,  C5, C10, C15, C20, C30, C40  Hemiterpenes consist of a single isoprene unit  Isoprene itself is considered the only hemiterpene TERPENOIDS --IMPORTANT MOLECULES  C5-hemiterpenes -e.g. Isoprene  C10-monoterpenes -e.g. Limonene  C15-sesquiterpene -e.g. Abscisic acid (ABA)  C20-diterpene -e.g. Gibberellin  C30-triterpne -e.g. Brassinosteroids  C40-tetraterpenes -e.g. Carotenoids  > carbons -polyterpenes-e.g. Ubiquinones, Rubber  Monoterpenes consist of two isoprene units and have the molecular formula C10H16.  Examples: geraniol, limonene and terpineol.  Sesquiterpenes consist of three isoprene units and have the molecular formula C15H24.  Examples: humulene, farnesenes, farnesol.  Diterpenes are composed of four isoprene units and have the molecular formula C20H32.  They derive from geranylgeranyl pyrophosphate.  (precursor of taxol).  Sesterterpenes, terpenes having 25 carbons and five isoprene units, are rare relative to the other sizes  Example: geranyl farnesol.  Triterpenes consist of six isoprene units and have the molecular formula C30H48.  The linear triterpene squalene, the major constituent of shark liver oil  Squalene is then processed biosynthetically to generate either lanosterol or cycloartenol , the structural precursors to all the steroids.  Sesquarterpenes are composed of seven isoprene units and have the molecular formula C35H56.  Sesquarterpenes are typically microbial in their origin.  Example: ferrugicadiol  USES:  Vitamin A representative Diterpenes  Squalene (shark liver oil) isoprene units (triterpenes)  Farnesol used as:  1. Perfumes  2. Pesticides  3. Pheromones  4. Anti- tumour agent  5. Antibacterial drug   Taxol is a terpenoid  "the best anti-cancer agent” by National Cancer Institute  Has remarkable activity against advanced ovarian and breast cancer, has been approved for clinical use. PHENOLICS  The final type of secondary metabolites has recently become very popular due to their health benefits: the phenols.  The phenols consist of a hydroxyl group (–OH) attached to an aromatic ring.  Phenols are found in nearly all parts of the plant and in nearly every plant on the planet.  The first group of phenols is the flavonoids.  Flavonoids are water-soluble pigments found in the vacuoles of plant cells.  Flavonoids can be further divided into three groups: anthocyanins, flavones and flavnols. FLAVINOIDS  One of the largest classes of phenolics  Carbon skeleton has 15 carbons with two benzene rings connected by a 3-C bridge ANTHOCYANINS  Colored flavinoids - red, pink, blue, purple pigments  Attract animal pollinators and seed dispersers  Anthocyanins range in color from red to blue and purple.  The color depends on the pH of the environment.  Anthocyanins are mostly found in grapes, berries and have a wide range of health benefits.  Use to protect against heart disease, diabetes and even cancer when they are consumed.  They are also appearing in skincare products to slow down the aging process.  The next two groups have white or yellow pigments.  They are called flavones and flavnols.  Phenols attract pollinators to the plants and even impact how plants act with one another. FLAVONES AND FLAVONOLS  Also flower pigments  Absorb UV not visible light - not visible to human eye but visible to many insects - maybe be attractants, nectar guides  Also present in leaves where they protect against UV- damage  Appeared to be involved in legume roots in attracting N- fixing bacteria ASPIRIN  Medically relative phenol is salicylic acid, which is the active ingredient in aspirin.  It comes from the bark of the willow tree.  It has been used to effectively treat aches and fevers  It also has cosmetic uses. GLYCOSIDES  A molecule in which a sugar is bound to another functional group via glycosidic bond  Compound formed from a simple sugar and another compound by replacement of a hydroxyl group in the sugar molecule.  Many drugs and poisons derived from plants are glycosides.  More important in medicine than a lot of drugs  Glycosides Action Great efficacy in numerous heart ailments, for example, congestive heart Cardiac glycosides failure, arrhythmia. Alcoholic glycosides Antiinflammatory, antipyretic and analgesic effects Steviol glycosides Natural sweetener Thioglycosides Allelopathic, antiseptic effects Phenolic glycosides Urinary antiseptic effect Antirheumatic, antiseptic, antiinflammatory, imparts characteristic color Anthocyanins to the flowers Cyanogenic glycosides Protects against predators through their unpalatability Anthraquinone Laxative and purgative effects Dilate coronary arteries, block calcium channels, antispasmodics, Coumarin antibiotics Flavonoid glycosides Strengthen blood capillaries by decreasing its fragility, antioxidant effect Expectorant, antiinflammatory effects, diuretics, and urinary tract Saponin disinfectants LATEX  Found in nature is a milky fluid found in 10% of all flowering plants (angiosperms).  It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums that coagulate on exposure to air.  It is usually exuded after tissue injury.  In most plants, latex is white, but some have yellow, orange  It serves mainly as defense against herbivorous insects.  Natural rubber is the most important product obtained from latex  It is used to make many other products as well, including mattresses, gloves, and balloons in chewing gum, and glues ESSENTIAL OIL  An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants.  Also known as volatile oils, ethereal oils  They are used in perfumes, cosmetics, soaps and other products, for flavoring food and drink, and for adding scents to incense and household cleaning products  It is used in numerous skincare products to treat acne, large pores and dermatitis.  The final type of phenol is important to the structure of the plant and is called lignin.  It adds stiffness and strength to cell walls of the plant cells.  Lignin supports the branches and size of terrestrial plants  It also allows the cell wall to be waterproof and protects the plant from fungal attacks. Thank you