Secondary Metabolites: Functions, Examples and Structures PDF

SECONDARY METABOLITES PRIMARY METABOLITES „ Molecules which are products of major pathway and directly involved in plant’s vital processes „ Found in all plants „ Commercially important as food sources „ Examples: carbohydrates (sucrose, starch, cellulose) proteins (amino acids)...

SECONDARY METABOLITES PRIMARY METABOLITES „ Molecules which are products of major pathway and directly involved in plant’s vital processes „ Found in all plants „ Commercially important as food sources „ Examples: carbohydrates (sucrose, starch, cellulose) proteins (amino acids) lipids (fatty acids) nucleic acids chlorophyll SECONDARY METABOLITES „Metabolic diversion of a product from a major pathway „Restricted in distribution „Function in plant defense, pollination and competition „Commercially important in medicines and industries PRINCIPAL GROUPS OF SECONDARY METABOLITES (BASED ON BIOSYNTHETIC CRITERIA) „ Terpenoids – from acetyl coA via mevalonic acid pathway Examples: essential oils (menthol, camphor), lycopene, limonene, saponin, taxol, carotenoid, sterol, rubber PRINCIPAL GROUPS OF SECONDARY METABOLITES (BASED ON BIOSYNTHETIC CRITERIA) „ Phenolics – from erythrose-4-phosphate and phosphoenol pyruvate via shikimic acid pathway Examples: simple phenolics (vanillin, salicylic acid), flavonoids (anthocyanin, flavone and isoflavonoid), lignin, tannin PRINCIPAL GROUPS OF SECONDARY METABOLITES (BASED ON BIOSYNTHETIC CRITERIA) „ Nitrogen-containing compounds – from amino acids Examples: alkaloids, cyanogenic glycosides, non-protein amino acids (canavanine) SOME WELL-KNOWN ALKALOIDS FUNCTIONS OF SECONDARY METABOLITES „ Defend plants against herbivore and pathogen attack (primary function) Examples: terpenes (essential oils, saponin, rubber) phenolics (lignin, tannin, isoflavonoid) nitrogen-containing compounds (alkaloid, cyanogenic glycoside) „ Serve as attractants for pollinators and fruit-dispersing animals Examples: terpenes (carotenoid) phenolics (anthocyanin, flavone) nitrogen-containing compounds (betacyanin) „ Agents of plant-plant competition Examples: simple phenolics WHY ARE PLANTS NOT POISONED BY THEIR OWN TOXIC SECONDARY METABOLITES? „ Stored as inactive precursors separate from their activating enzymes „ Have modifications rendering them insensitive to the toxic effects „ Stored away from sensitive metabolic processes