Plant secondary metabolites Dr. Muayad S. Shawkat University of Baghdad College of Science Department of Biotechnology

Plant secondary metabolites are a diverse group of molecules that are involved in the adaptation of plants to their environment but are not part of the primary biochemical pathways of cell growth and reproduction. These compounds are played many important rules in plant life such as involved in defense against herbivores and pathogens, regulation of symbiosis, control of seed germination, and chemical inhibition of competing plant species (allelopathy), and therefore are an integral part of the interactions of species in plant and animal communities and the adaptation of plants to their environment.

In addition, plant secondary metabolites are also associated with improved nutritive value and may have beneficial effects on animal health. Growing interest in the potential health-promoting effects of plant secondary metabolites in human foods has prompted research on their potential to prevent or treat cancer, circulatory disease, and viral infection. The mechanisms by which these substances have beneficial effects on health may also be related to their toxic effects, and the difference between toxicity and beneficial effects may be dose- and structure-dependent. The term “plant extract" determines the part/parts of a plant used for preparing medicine (for example: leaves, flowers, seeds, roots, barks, stem....etc). Studies on the use of plant extracts for controlling disease have shown the importance of natural chemicals (phytochemicals) as possible sources of non-phytotoxic and easily biodegradable, alternative fungicides and antibiotics

Preparing the plant Material: Plants were dried before extraction. freeing of plant under study from contamination From other plants from disease Extraction: as the term is used pharmaceutically, involves the separation of medicinally active portions of plant or animal tissues from various parts of plants by using selective solvents in standard extraction procedures. Selection of the solvent depends on the polarity of solvent and solubility of the desired components of the material.

General methods Extraction: choosing of the precise method of extraction depend on texture and water content of the plant material. Maceration the whole or coarsely powdered crude drug is placed in a container with the solvent and allowed to stand at room temperature for a period of at least 3 days with frequent agitation until the soluble matter has dissolved.

2. Hot Continuous Extraction (Soxhlet) In this method, the finely ground crude drug is placed in a porous bag or “thimble” made of strong filter paper, which is placed in chamber E of the Soxhlet apparatus. The extracting solvent in flask A is heated, and its vapors condense in condenser D. The condensed extractant drips into the thimble containing the crude drug, and extracts it by contact. When the level of liquid in chamber E rises to the top of siphon tube C, the liquid contents of chamber E siphon into flask A.

CO2 Photosynthesis Primary carbon metabolism pyruvate Pentose phosphate pathway Phosphoenol pyruvate Acetyl Co-A TCA Cycle Erythrose-4-phosphate Aliphatic amino acid Shikimic acid Malonic acid Pathway Nitrogen containing compounds Mevalonic acid Pathway Aromatic amino acids Phenolic compounds Terpenes

Main Groups of plant secondary metabolites A/ Terpenoids B/ Nitrogen containing secondary metabolites C/ Phenolic compounds

The 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

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

Nitrogen containing compounds! Alkaloids (pseudo-, True-, proto-) Extremly heterogenous group alkali like have important pharmacological properties further classified in to 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. resrpine Imidazol alkaloids , e.g. pilocarpine

Pyridine and piperidine e.g. lobeline, nicotine Phenylalkylamines: e.g. Ephedrine Pyridine and piperidine e.g. lobeline, nicotine Tropane e.g. Atropine.

Quinoline e.g.quinine and quinidine Isoquinoline e.g. papaverine Phenantheren e.g. Morphine

Indole e.g.ergometrine Imidazole e.g. pilocarpine Purine e.g. caffeine

Steroidal e.g. Solanum and Veratrum alkaloids Terpenoid e.g. Taxol

Cyanogenic glycosides widely distributed in plants volatile poisons e.g. Lotustraline Glucosinolates contain nitrogen and sulpher volatile toxins strong deterrent

Cyanogenic Glycosides

Non-Protein amino acids found in plants of the family leguminosae e.g. Canavanine resemble in structure with arginine there are not incorporated in to protiens

Phenolics Plants produce a variety of compounds that contain one or more phenol groups - called phenolics Thousands of phenolics occur in plants

Phenolics Large group of diverse compounds Many serve as defense compounds against herbivores and pathogens Some function in support – primary cmpd Some attract pollinators Some absorb UV light Some reduce growth of competitors

Tannins They are high molecular weight phenolic compounds They are widely distributed in plants. capable of precipitation of animal proteins

Classification of Tannins: Not hydrolysable, no sugar in mol.

Uses of Tannins: 1) Antioxidant. 2) Antidiarrheal. 3) Antidote for heavy metals poisoning. 4)Treatment of burns, ulcers, inflammations 4) Astringent to stop bleeding (hemorrhage) 5)Treatment of Hemorrhoids. 6) Tanning industry.

Lignin a complex phenolic Primary metabolite - secondary cell wall component occurs in all vascular plants Structural function Also protective because deters herbivores due to its toughness Blocks growth of many pathogens because only small group of fungi can degrade

Flavinoids One of the largest classes of phenolics Carbon skeleton has 15 carbons with two benzene rings connected by a 3-C bridge -C3-

Anthocyanins Colored flavinoids - red, pink, blue, purple pigments Attract animal pollinators and seed dispersers

cyanidine 3-rutinoside Anthocyanin cyanidine cyanidine 3-glucoside cyanidine 3-rutinoside B peonidine peonidine 3-glucoside peonidine derivative 안토사이아닌의 색은 고리B에 결합한 치환기에 의해 결정되는데 OH기의 숫자가 증가하면 장파장의 흡수가 잘되서 청색을 나타내며 OH기가 CH3(메틸)기로 치환되면 단파장이 잘 흡수되어 더 적색을 나타낸다. 그래서 OH기가 3’, 4’ 위치에 붙어있는 시아니딘은 적자주색을 나타내고, 3’이 메틸기로 치환된 피오니딘은 다홍색을 나타낸다.

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-B damage Appeared to be involved in legume roots in attracting N-fixing bacteria

Some applications of Important plants and their compounds in biotechnology

Green Tea (Camellia sinensis) Polyphenols from leaves anti-cancer inhibiting tumor initiation and cell proliferation anti-oxidant

Wine Grape (Vitis vinifera) Contains over 50 different flavonoid phenolics including resveratrol and catechins Reduces heart disease by inhibiting platelet aggregation, lowering LDL (low density lipoproteins) and acting as antioxidants

Ginger (Zingiber officinale) from the rhizome Over 12 compounds with anti-oxidant activities greater than vitamin E anti-tumor anti-emetic (inhibits vomiting)

Garli c (Allium sativum) Onion (Allium cepa) Organo-sulfur compounds from leaves Anti-carcinogenic and anti-microbial Anti-atherosclerosis and anti-hypertensive Toxic in high amounts

Soybeans (Glycine max) Contains phytoestrogens like isoflavones Reduces health risks associated with menopause: osteoporosis and heart disease in women Reduces prostrate, colon and breast cancer

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