Chapter 3 - Secondary Metabolites PDF

**[CHAPTER 3 - SECONDARY METABOLITES]** 1. Alkaloids: a. These **basic** compounds have **one or more nitrogen** atoms as a part of **heterocyclic** system. b. They are often toxic to humans especially when taken in high doses. c. **Precursors of alkaloids are ami...

**[CHAPTER 3 - SECONDARY METABOLITES]** 1. Alkaloids: a. These **basic** compounds have **one or more nitrogen** atoms as a part of **heterocyclic** system. b. They are often toxic to humans especially when taken in high doses. c. **Precursors of alkaloids are amino acids** such as aspartic acid, lysine, tryptophan, and tyrosine. d. They are mostly found in flowering plants. e. Many of the plant alkaloids are specific and are present in a definite plant species. f. Alkaloids have been studied for wide range activities including anticancer, anti-cholinergic, diuretic, antihypertensive, emetic, antimicrobial, antiviral, anti-inflammatory, antidepressant and anti-diarrheal activity g. Examples of alkaloids drugs (): i. Morphine ii. Quinine iii. Ephedrine iv. Strychnine v. Nicotine 2. Glycosides: h. These compounds are composed of a carbohydrate (glycone) and a non-carbohydrate (aglycone) part. The two parts are joined together by glycosidic bond. i. **Biological activity of glycosides mainly depends on the chemical nature of the aglycone part**. j. Cardiac glycosides, an important class of glycosides they are used in the treatment of different CVS disorders, and recently for neurodegenerative diseases and cancer. k. Some **glycosides such as glucosinolates and cyanogenic glycosides** produce cyanide compounds that are highly toxic for their predator. l. It's important to know the sugar form the non- sugar part, to identify it's a glycoside or not. 3. Phenolics: m. These are the compounds **having "OH" group** present in their structure. n. Flavonoids, tannins, lignins, anthocyanins and phytoalexins are all included in phenolics. o. phenolic compounds also impart some organoleptic characteristics like color, odor and taste to many plant species. p. Their subtypes include:  4. Flavonoids: q. Flavonoids are phenolic compounds having a **fifteen-carbon nucleus**. r. They exist either freely (aglycones) or in conjugation with sugars such as D-glucose or as methylated derivatives. s. Flavonoids possess activities such as antimicrobial, antioxidant, anti-gout, anti-inflammatory, anti-atherosclerotic, anti-thrombogenic, anti-ulcer, antidiabetic, vasorelaxant, oestrogenic, anticancer, spasmolytic and hepatoprotective activities. They have also been found to be useful in the treatment of CVS diseases. 5. Tannins: t. These are high molecular weight polyphenolic compounds and exist in the form of polymers of flavonoids. u. These are water soluble and have the ability to bind with different enzymes and proteins, making them inactive. vi. Insects which feed on such plants die due to undernourishment and enzymatic failure. v. The **astringent** action of many plants is due to the presence of tannins in them w. Tannins can be classified into two major groups namely; vii. Hydrolysable tannins viii. condensed tannins x. Hydrolysable tannins (Toxic to Humans) contain glucose molecules esterified with phenolic compounds ix. Enzymes known as tanninases hydrolyze the esters present in molecules. They are usually harmful to the human body and may damage liver, kidney and GIT. x. Those tannianses enzymes also helps them to bind to different enzymes and proteins of insects or predators in general to kill and protect themselves. y. Condensed tannins (Safe to Humans) consist of large number of flavonoid units linked to each other by carbon-carbon bonds. 6. Terpenoids: z. Most abundant of all chemical classes. a. Classified into monoterpenoids, diterpenoids, triterpenoids and sesquiterpenoids b. This classification is based on the presence of the number of isoprene units (C5H8) in the structure. c. The **essential oils** found in plants mainly comprises of mono and sesquiterpenoids d. Oils usually have fragrance and also protect plant from excessive heat and from insect attack. 7. Steroids and sterols: e. The structure of plant **sterols is similar to that of cholesterol** consisting of a **cyclopentenophenanthrene ring**. f. Steroids have a structure closely resembling to that of sterols g. In plants they are mostly combined with sugars to form glycosides. h. Plant sterols and steroids possess biological activities such as anticancer, antimicrobial and antihypercholesterolemic activities. 8. Saponins: i. Compounds having soap like properties as they produce frothing when their aqueous solution is vigorously shaken. j. Contain **triterpenoids attached with sugar groups** k. Biological activities including antifungal, antiparasitic, antidiabetic, anti-inflammatory and expectorant properties. l. They are toxic if injected due to their ability to cause **haemolysis**. 9. Detection of alkaloids: S.NO TEST NAME RESULTS ------ --------------- ----------------------------------- 1 Mayer's White or creamy precipitates 2 Valser's White precipitate 3 Wagner's Reddish brown precipitate 4 Dragendorff's Reddish brown precipitate 5 Hager's Production of yellow precipitates 10. Detection of Glycosides: m. Borntragers test n. Legals test 11. Phenolics and tannins: o. FeCl3 test p. Gelatin test q. Lead acetate test r. Alkaline reagent test  12. Toxic plants: s. They cause the following side effects: xi. Skin Irritation xii. Allergic reactions xiii. Mild GIT disturbance xiv. Highly toxic plants t. **Water Hemlock:** xv. Active ingredient: Cicutoxin xvi. MOA: 1. non-competitive antagonist of the gamma-aminobutyric acid (GABA) receptor xvii. Effect of the toxin: 2. Painful convulsions, abdominal cramps, nausea, and death 3. who survive are often afflicted with amnesia or lasting tremors u. **Deadly Nightshade (*Atropa belladonna*):** xviii. Active ingredients: 4. Atropine and Scopolamine xix. Route of transmission: 5. physical contact with the leaves may cause skin irritation. xx. Effect of the toxin: 6. causes paralysis in the involuntary muscles of the body, including the heart. v. **White Snakeroot:** xxi. Active ingredient: **Tremetone** xxii. Route of transmission: 7. meat and milk from poisoned livestock can pass the toxin to human consumers xxiii. Effect of toxin: 8. Cytotoxic and hepatotoxic 9. loss of appetite, nausea, weakness, abdominal discomfort, reddened tongue, abnormal acidity of the blood, and death. w. **Rosary Pea:** xxiv. **Active ingredient:** Abrin, ribosome-inhibiting protein. xxv. Route of transmission: 10. Jewellery 11. seeds that are scratched, broken, or chewed can be lethal. xxvi. Effect of toxin: 12. prevents protein synthesis within cells and can cause organ failure x. **Oleander:** xxvii. **Active ingredient:** lethal cardiac glycosides known as **oleandrin and nerine** xxviii. Route of transmission: 13. Eaten 14. Skin contact with the leaves. xxix. Effect of toxin: 15. eaten, oleander can cause vomiting, diarrhea, abnormal pulse, seizures, coma, and death 16. contact with the leaves and sap is known to be a skin irritant