4.1.4.2 Comprising of C, H, and O only: A wide spectrum of plant constituents containing C, H and O have been identified.
Examples:
(A) Alcohols:
(a) Geraniol (or Lemonol): It is an olephenic terpene alcohol constituting the major portion of oil of rose and oil of palmarosea. It is also found in many volatile oils, for instance: citronella, lemon grass etc.
(b) Menthol (or Peppermint Camphor): It is a monocyclic terpene alcohol obtained from peppermint oil or other mint oils or prepared synthetically on large scale by carrying out the hydrogenation of thymol.
(B) Aldehydes:
(a) Citral: It is an aliphatic terpene aldehyde present in oil of lemon grass, lemon, lime, ginger
root and in the oils of several Citrus species etc. The citral from natural sources is a mixture
of two isomers geraniol and neral.
(b) Vanillin: It is a cyclic terpene aldehyde. It occurs in vanilla in potato parings, in Siam benzoin, Peru balsam, clove oil etc. It is made synthetically either from guaiacol or eugenol; also from waste (lignin) of the wood pulp industry.
(C) Ketones:
(a) Carvone: It is a monocyclic terpene ketone. dl-Carvone is found in gingergrass oil; d-carvone is found in caraway seed and dill seed oils, l-carvone is found in spearmint and kuromoji oils.
(b) Camphor: It is a bicyclic terpene ketone. It naturally occurs in all parts of the camphor tree, Cinnamonum camphora T. Nees & Ebermeier; while 3/4th of the camphor consumed in USA is manufactured from pinene as the racemic form.
d-camphor: is found in oil of sassafras, rosemary, lavender and sage;
l-camphor: is found in lavender and artemisia;
dl-camphor: is found in oil of sage and in oil of Chrysanthemum sinense var. japonicum.
(D) Phenols:
(a) Thymol: It is a monocyclic phenol. It is obtained from the volatile oil of Thymus vulgaris L. and Monarda punctata L. and several spices of Ocimum. Commercially it is synthesized from p-cymene, m-cresol and piperitone.
(b) Eugenol (or Allyguaicol): It is a dihydric phenol and is the main constituent of several important essential oils, such as: oil of clove, oil of cinnamon leaf, oil pimenta.
(c) Myristicin: It is a trihydric phenol occurs in oils of nutmeg, mace, French parsley, dill oils and carrot.
(d) Apiole: It is a tetrahydric phenol which occurs in Dill oil (Anethum graveolus L.) and known as Apiole (Dill); and also in Parsley oil (Petroselinum sativum Blanchet, Sell) and termed as Apiole (Parsley).
(E) Quinones:
Examples:
Anthraquinone Glycosides: A plethora of glycosides having aglycone moieties related to anthracene are present in such drugs as aloe, rhubarb, senna, frangula and cascara sagrada. In general, the glycosides on hydrolysis give rise to corresponding aglycones which are di-, tri-, or tetrahydroxyanthraquinones or invariably structural modifications of these compounds.
Examples: Frangulin-A upon hydrolysis yields emodin and rhamnose as shown below:
(F) Acids:
(a) Caffeic acid: It is the constituent of plant and isolated from green coffee beans. It probably occurs in plants only in conjugated forms e.g. chlorogenic acid.
(b) Ferulic acid: It is widely distributed in small amounts in various plants species. It is isolated from Ferula foetida Reg.
(G) Esters:
(a) Pyrenthrins (Pyrethrin I & Pyrethrin II): It is the active insecticidal constituents of pyrethrum flowers.
(b) Methyl Salicylate: It is present in a number of oils, namely: wintergreen oil, betula oil, sweet birch oil, teaberry oil.
(H) Lactones:
(a) Podophyllotoxin (Syn: Condyline, Podofilox, Martec): It is an antineoplastic glycoside found in the rhizomes of North American Podophyllum peltatum L.
(b) α-Santonin: It is an anthelmintic isolated from the dried unexpanded flower heads of Artemesia maritima L., sens lat.
(I) Terpenoids:
(a) Gibberellins: It represents a class of plant growth hormones first isolated from the cultures of Gibberella fujikuroi (Sawada) Wollenweber.
(b) Primaric Acid: It is obtained from American rosin, French galipot and from Pinus maritima
Mill.
(J) Carotenoids:
(a) Xanthophyll (Syn: Vegetable lutein; Vegetable lutenol; Bo-Xan): It is one of the most widerpread carotenoid alcohol present in nature. It occurs in egg-yolk, nettles, algae, and petals of many yellow flowers. It also occurs in the coloured feathers of birds.
(b) β-Carotene: It is most abundantly distributed in the plant and animal kingdom. In plants it occurs invariably with chlorophyll. It acts as a precursor of Vitamin A. It was first isolated from carrots and hence bears its name. It usually represents the natures ‘red’ colouration in plant kingdom.
(K) Steroids:
(a) Cevadine: It is one of the steroidal alkaloids obtained from Veratrum viride. American or Green hellebore from its dried rhizome and roots.
(b) Digitoxin: It is a cardiotonic steroidal-glycoside obtained from Digitalis purpurea L;D. lanata and other species of Digitalis. About 10 Kilo leaves yield only 6 Grams of pure digitoxin.
(c) Ergosterol: It is usually obtained from yeast that synthesizes it from simple sugars such asglucose. The damp yeast yield about 2.5 g ergosterol; however, the particular variety of yeast is very important.
REFERENCES
Ashutosh Kar (2003), Pharmacognosy and Pharmaco biotechnology, 2nd Edition
‘Handbook of Medicinal Herbs’ (2001), J.A. Duke, CRC-Press, London, 1st Edn.
William Charles Evans (2002), Trease and Evans Pharmacognosy 15th Edition by: Trease, Bailliere Tindall; Evans.
Ramstad (1956), E., ‘Modern Pharmacognosy’, McGraw Hill, London.
