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Plant Metabolites & Ergastic Cell Contents

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Plant Metabolites & Ergastic Cell Contents

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  1. Plant Metabolites & Ergastic Cell Contents

  2. Primary metabolites chlorophyll AA’s Nucleotides Simple CHO’s Membrane lipids *** ARE FOUND THROUGHOUT THE PLANT KINGDOM Fx: Important roles in growth and development photosynthesis respiration solute transport translocation nutrient assimilation differentiation Primary Metabolites

  3. Definition: All organic compounds Have no direct function in growth and development Also called secondary products or natural products Differ from 1º metabolites in that they have a restricted distribution in the plant kingdom Therefore: Only particular secondary metabolites are found in only one specific plant species or a taxonomically related group of species. Secondary Metabolites

  4. Secondary Metabolite Fx • Initially thought to be functionless end products of metabolism or metabolic waste products • Responsible for characteristics, odours, pungencies & colours of plants. Others give plants their medicinal, culinary or poisonous values. • They are synthesized to aid the producing plant’s survival.

  5. Secondary Metabolite Function • Ecological functionsin plants: protect against herbivory • Protect against infection by microbial pathogens • Attract pollinators & seed distributing animals • Act as agents for plant-plant competition

  6. Evolution of 2º Metabolites • 2º Metabolites evolved through mutations in the basic metabolic pathways •  appearance of new compounds • happened to be toxic or a deterrent to herbivores and pathogens • As long as they were not toxic to the plant itself and were produced at a low metabolic cost • They gave the plants containing them greater reproduction fitness than undefended plants (plant-plant competition) • Undefended plants therefore left more descendants while the protected plants left less • And passed their defensive traits on to the next generation

  7. The defence compounds (secondary metabolites) that increase reproductive fitness of plants by warding off fungi, bacteria and herbivores, also make them undesirable as food by humans. • Many NB crop plants have been artificially selected for producing relatively low levels of these compounds, which make them more susceptible to insects and disease • (e.g. of Wheat)


  9. Terpenes • Terpenes are lipids • synthesized from acetyl CoA or from the basic intermediates of glycosides

  10. Phenolic compounds • Phenolic compounds arearomatic substances • Formed via the Shikimic acid Pathway or the Malonic acid pathway

  11. Nitrogen-containing compounds • e.g. alkaloids • synthesized from AA’s

  12. Active Plant Constituents

  13. Sugars (glucose, xylose) Starches (energy stores) Cellulose (structural support) Gums & mucilage Carbohydrates

  14. Very complex CHO’s Found in excellent vulnerary, demulcent & emollient herbs. E.g. Marshmallow & Plantain Gums & Mucilages

  15. Relax Gut lining Relax Respiratory System Reduce irritation and inflammation (GIT, Respiratory, US) MO: soak up large amounts of water  sticky jelly: dry irritated skin, inflamed/painful tissues Some stimulate immune system: e.g. Acemannan (Aloe vera) Gums & Mucilage Fx

  16. Occurs in plants in various forms Constituent of volatile oils & sterols Attar of Rose Menthol in peppermint Waxes (beeswax) Cutins Plant Alcohols

  17. Phenol = basic building block for many plant constituents Simple/complex in nature Fx: anti-inflammatory Anti-septic E.g. Salicylic acid (Willow) Eugenol (Clove) Thymol (Thyme) Phenols

  18. Anti-spetic (Garlic/Thyme oil) Stimulate tissue  irritation e.g. Mustard  numbing e.g. Camphor oil). Aid digestion CNS action Insect repellent Anti-inflammatory Anti-allergenic Volatile Oil Function

  19. Closely related to tannins & flavonoids Phenols Fx: powerful anti-oxidants Protect circulation from damage: especially circulation of the heart, hands, feet & eyes. E.g. Crataegus spp. Proanthrocyanins

  20. Fx – give herbs their astringent & heamostypic action Act on proteins and form a protective layer on the skin & mucous membranes Bind the tissues of the gut Reduce diarrhoea & internal bleeding Externally: Rxing burns, sealing wounds & reducing inflammation. Heal infections of the eye, mouth, vagina, cervix & rectum (mucous membrane tissues) Tannins - phenols Tannins

  21. (smell of cut grass) Limited effects on the body Di-coumarol, (metabolite)  powerful anti-clotting agent. Functions: Allopathic: Basis for warfarin (thrombosis in small doses): Horse Chestnut (Rat poison in large doses) Visnaga – powerful smooth muscle relaxant Coumarins

  22. Plants containing anthraquinones  effective purgatives (& good natural dyes) Senna & Aloe Also make stool more liquid (Constipation) Fx: gently stimulate colon 8-12 hrs after ingestion (stimulate peristalsis) Can only Fx when natural bile is present. Tend to cause colonic pain (over-stimulate colon wall) Anthraquinones

  23. Glycosides • Flavonoids • Saponins • Phenolic glycosides • Cardiac Glycosides • Cyanogenic Glycosides

  24. One of the most common group of plant constituents Polyphenols Wide range of actions Anti-spasmoidic Anti-inflammatory Anti-oxidant Diuretic Circulatory Stimulants Cardiac stimulants Anti-viral hepatic Flavonoids

  25. Pharmaceutical Chemists  synthesis of cortisone (anti-inflammatory) & sex hormones Saponins in herbs do not act in the same way  body can use them as building blocks to form appropriate chemicals. Fx: anti-inflammatory Expectorant Aid nutrient absorption Saponins

  26. Discovered from Foxglove (1785)  recognised to support a failing heart Many flowering plants contain cardiac glycosides Fx: increase heart efficiency Steady tachycardia NO CARDIAC STRAIN Strong diuretic Cardiac Glycosides

  27. Based on cyanide (toxic) Small doses Sedative Relaxant effect on heart & muscle Wild cherry bark: suppress & soothe dry, irritating coughs. Fruit kernels (apricot) Cyanogenic Glycosides

  28. Group of chemicals with an exceedingly bitter taste Wide diversity of structure Most belong to the iridoids, some to terpenes Fx: stimulate digestive juices & appetite Aid the liver Anti-biotic Anti-fungal Anti-tumour Play specific roles depending on herb & chemical combination e.g. Valerian & Devil’s claw Bitter Principles

  29. The most potent group of plant constituents Effect: body & mind Some: effect on lungs, liver, nerves, GIT Fx in plant: ± source of excessive N2. (makes them pharmacologically active). Divided into 13 groups based on their chemical structure (no general effects) E.g. Atropine (Atropa belladonna)  reduce spasms, relieve pain & dry up bodily secretions Alkaloids

  30. Found exclusively in the Brassica Family (Mustard & Cabbage) Instant blistering & inflammatory effect on the skin Applied to painful areas to increase blood flow Helps remove excessive waste products Eating: produce a strong pungent taste. Glucosilinates

  31. Found in many medicinal plants Lemon peel: Vitamin C Carrot: Vitamin A Brewers Yeast: B-vitamins Nasturium/watercress: Vitamin E Vitamins

  32. Minerals • Plants draw minerals from the soil and convert them into a form which is easily absorbed & used by the body. • Kelp: I2 • Dandelion: K • Horsetail: Silica • Nettle: Fe & Ca • Brewers Yeast: Chromium


  34. Calcium Oxalate • Numerous crystals occur in plants • Ca-oxalate is one of the most common • Like trichomes & stomata, it also has diagnostic value • X polymorphs are characteristic in x plant spp.

  35. Crystal Systems • In plants  2 crystal systems exist • All crystal polymorphs belong to one of these systems • Systems • Tetragonal System • Monoclinic System • Systems differ • in the amount of water they attain • OD

  36. Composition: CaC2O4.3H20 Arises from supersaturation of the cell sap with calcium oxalate Includes Prisms Cluster crystals (rosette aggregates) microsphenoids Tetragonal Crystal System

  37. Monoclinic Crystal System • Chemical composition: CaC2O4.H20 • Form in the presence of excess oxalic acid • Crystal forms include • Some prisms • Needle-like crystals (raphides) • Sphaero-crystals

  38. When using Calcium oxalate crystal types as a diagnostic tool: Crystal type Size Distribution Should all be noted. NB!!!

  39. Crystal Function • Uncertain • More abundant in plants growing in arid regions. • Ca: Causes epithelial cells to swell • Deter herbivory?

  40. Crystal Forms • Prisms • Cluster Crystals • Microsphenoids • Raphides • Sheaero-crystals

  41. Found in Cardamom Small single prisms Starch masses in parenchyma Prisms – Elletaria cardamomum

  42. Black henbane Single prisms Some have a crystalline outgrowth (plug) Twin prisms In crystal layer of spongy mesophyll cells (directly below palisade tissues) Prisms – Hyosciamus niger

  43. Senna * Single prisms * Occurs in parenchyma cells * Surrounds bundles of pericyclic fibres * Forms a crystal sheath Prisms – Cassia senna

  44. Found in Liquorice * Single prisms * Occurs in parechyma tissue * Surrounds xylem & phloem * Forms an incomplete crystal sheath Prisms – Glycyrrhiza glabra

  45. Cascara senega Crystal sheaths Similar to liquorice Occurs with the phloem fibres Complete crystal sheaths Prisms – Rhamnus purshianus

  46. Atropa belladonna Aggregates occur in a crystal layer Below palisade tissues When a single cell contains an aggregate of microsphenoids  idioblast Microsphenoids

  47. Occur Singly E.g. Ipecavanha In bundles E.g Squill Raphides

  48. Diagnostic Value of Calcium Oxalate Crystals • Absence of crystals • Different form • Different size  all used to identify adulterants or allied species from medicinal herbs.

  49. E.g. Digitalis purpurea: (used medicinally) no calcium oxalates D. thapsi: (not used medicinally) - small prisms Diagnostic Value of Calcium Oxalates

  50. E.g. Atropa belladonna: Leaves have micro-sphenoids Phytolacca leaves: have raphides Diagnostic Value of Calcium Oxalate Crystals