Secondary metabolites

Metabolites, Secondary metabolites are derived from primary metabolites, Why secondary metabolites, Phenolics, Terpenoids, Alkaloids, Special nitrogen metabolites, Cuticular compounds .The major classes of these found in plants

1. FUNDAMENTALS OF BIO CHEMISTRY (BIC – 102) Submitted by, Jayasankar.p (2015037019) SECONDARY METABOLITES

2. Metabolites Primary metabolites : Molecules that are essential for growth and development of an organism. Secondary metabolites : molecules that are not essential for growth and development of an organism.

3. Secondary metabolites are derived from primary metabolites

4. Why secondary metabolites? Chemical warfare to protect plants from the attacks by predators, pathogens, or competitors Attract pollinators or seed dispersal agents Important for abiotic stresses Medicine Industrial additives

5. SECONDARY METABOLITES Organic compounds produced by the plants which have no direct role in the growth and development are called as secondary metabolites. Estimates suggest that there are about 100,000 secondary compounds that are produced by the plants and the structures of more than 15000 alkaloids, 300 terpenes , several thousand phenyl propanoids , 1000 flavonids , 500 quinones , 700 polyacetylenes and 800 non- protien amino acids have already been characterized.

6. These secondary compounds produced by plants are grouped into five major groups. Phenolics Terpenoids Alkaloids Special nitrogen metabolites Cuticular compounds

7. PHENOLICS: Phenolics are a group of compounds characterized by at least one aromatic ring bearing one or more hydroxyl group. Most of the thousands of phenolics known to date are of plant origin. Phenolics are synthesized by the shikimate pathway . Phosphoenolpyruvate and erythrose-4-phosphate are the precursors for phenolics for phenolics biosynthesis.

8. The major classes of phenolics found in plants S.NO. class Carbon skeleton Example 1 . Simple phenols C6 catechol 2 . Hydroxybenzoates C6- C1 Gallic, catechuic acid, salicyclic acid 3. Hydroxycinnamates C6-C3 Caffeic acid, coumaric acid 4. Naphthoquinones C6-C4 Juglone

9. 5. Xanthones C6-C1-C6 Hydroxyxanthone 6. Stilbenes C6-C2-C6 Resveratrol 7. Flavonoids C6-C3C6 Quercetin 8. Polyphenols (C6-C3)n (C6-C3-C6)n Lignins , condensed tannins

10. Functions of phenolics : Phenolics are of great important as cell wall compounds.they form part of cell wall structures such as lignins , cutin and suberins , which provide mechanical support and function as barriers against microbial attack. The flavonoids and anthocyanins contribute to flower and fruit colours . This is important for attracting insescts and animals to the plant for pollination and seed dispersal. Plants rich in polyphenols were used as tanning agents in leather industries.

11. Phenolics also play a defensive role in plants by protecing against predators. Simple phenolic acids, polyphenolics like tannis and phenolic resins at the plant surface are effective feeding deterrents. Phenolic also function as single molecules in the interaction between nitrogen fixing bacteria and leguminous plants. These plants exude flavonoids which act selectively in Rhizobia as inducers of nodulation gene transcription. Phenolic pigments of fruits are most widespread food colours occurring in fruit juices, wines and jams. Anthocyanins have considerable potential in the food industry as safe and effective food additives.

12. More Phenolics Some phenolics form polymers . Tannins are astringent to the taste. They give dryness (astringency) to dry wines. They can also be used to tan leather. They often give water a tea-colored look. Tannins are common in pines and oaks. Lignin is a major structural component of wood. The exact structure of lignin is complex and not known.

13. Myristicin from Nutmeg

14. Anthocyanins

15. Tannins

16. Terpenoids Terpenoids are dimers and polymers of 5 carbon precursors called isoprene units (C 5 H 8 ). Terpenoids often evaporate from plants and contribute to the haze we see on hot sunny days. They are expensive to make; they often take 2% of the carbon fixed in photosynthesis; carbon that could otherwise be used for sugars.

17. Terpenoids : Terpenes are lipids which have the basic five carbon unit called isoprene. They are also called isoprenes . Plants produce a great variety of isoprenoids . Some of these are primary metabolites such as plant hormones , carotenoids and steroids . However, majority of these compounds are secondary metabolites. Terpenoids are biosynthesized by acetate- mevalonate pathyway . The precursor used is acetyl CoA . Terpenes are classified according to the number of five carbon units present in the molecule.

18. Classification of terpenoids class Number of carbons Hemiterpene 5 Monoterpene 10 Sesquiterpene 15 Diterpene 20 Sesterterpene 25 Triterpene 30 Tetraterpene 40 polyterpene 5n

19. Functions of terpenoids : Monoterpeniods interfere with basic metabolic, physiological, and behavioural functions of insects. Some exhibit acute toxicity, whereas otheres function as repellents, attractants, antifeedants or affect growth, development and reproduction . A number of monoterpenes possess antimicrobial activity. Steols are triterpenoids and play structural role in plants. Saponis and glycosidic triterpenoids protect plants against fungal attack.

20. Sesquiterpenoids function as feeding deterrents, insect juvenile hormones, pheromones and plant growth regulators abscisic acid . An alkaloid diterpene , ryanodine is one of the most potent naturally occurring insecticides against lepidopteran larvae. Some diterpenses such as agugarns and clerodin function as insect antifeedant . Gibberellic acids, are diterpenses that function as growth regulator. Hemigossypolone , gossypol and heliocides are toxic and antifeedants to several insects.

21. Beta-carotene

22. Pine Resin

23. Rubber Tapping

24. Alkaloids Alkaloids generally include alkaline substances that have nitrogen as part of a ring structure. More than 6500 alkaloids are known and are the largest class of secondary compounds. They are very common in certain plant families, especially: Fabaceae – peas and beans Asteraceae - sunflowers Papaveraceae - poppies Solanaceae – nightshade, tomato Apocynaceae - dogbanes Asclepiadaceae - milkweeds Rutaceae - citrus

25. ALKALOIDS: Alkaloids are nitrogen containing compounds having at leave some basicity . They usually heterocyclic and occur primarily in higher plants and some micro organisms. They usually exhibit significant physicological activity in humans and animals and represent one of the largest and most diverse groups of secondary products. Poisons – conine Narcotics – morphine Stimulants – caffeine Medicine – Taxol

26. Classification of alkaloids True alkaloids – possess heterocyclic ring and are derived from amino acids. Eg . Nicotine, Quinine. Protoalkaloids – Do not possess heterocyclic ring but are derived from amino acids. Eg , colchicine Pseudoalkaloids – Not derived from amino acids. Eg . Caffeine, theophylline .

27. Functions : Alkaloids play a defense role in plants against insets other arthropods and vertebrates . Some alkaloids have allelopathic effects. Some alkaloids possess physicological actions in humans . For example vinblastine and vincristine are potent anticancer drugs. Alkaloids act as reserve substances able to supply nitrogen. They are end products of detoxification meachanisms . Some alkaloids function as antimicrobial compounds.

28. Pharmaceutial uses of alkaloids Many alkaloids exhibit marked pharmacological activity, and some fine important uses in medicine. Atropine, present in datura species is used widely in medicine as anticholinergic drug. It is also used to dilate the pupil eye surgery. Morphine and codeine are narcotic analgesics, and codeine is also an antitussive agent, less toxic and less habit-forming than morphine. Colchicines, from the corms and seeds of the autumn crocus, is used as a gout suppressant. Caffenine , which occurs in coffee, tea, and cocoa is a central nervous system stimulant; it is used as a cardiac and respiratory stimulant and as an antidote to barbiturate and morphine pensioning.

29. Codeine from opium poppy

30. Atropine – from Belladonna aka Deadly Nightshade

31. Quinine from Chinchona

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