Distribution of Steroid like Compounds in Plant Flora
Medicinal herbs constitute an effective source of traditional (Ayurvedic, Unani and Homeopathy) and modern medicine. The plant is a biosynthetic laboratory, not only for chemical compounds, but also a multitude of compounds like glycosides, alkaloids etc. These exert physiological and therapeutic effect. The compounds that are responsible for medicinal property of the drug are usually secondary metabolites. Alkaloids, glycosides, neutral principles, resins, oleoresins, sesquiterpene lactones are some of the common active constituents of medicinal herbs. The article reviews distribution of steroid like compounds and their pharmacological importance.
1The practice of medicinal herbs for treating the diseases is very well known from ancient times. There are number of synthetic medicines which have been derived from medicinal herbs. Digioxin, Aspirin, Reserpine, Ephedrine, Quinine, Vincristine, Vinblastine, Taxol, Artemisinin, Hypericin, Silymarin are some noteworthy examples and their mechanism of action is beyond doubt as far as efficacy is concerned. Number of studies is available to show their effectiveness. These are regarded as active constituents of the herbs and are present in standardized form in the herbal extracts, if not isolated as single entity.
In addition to the alkaloids, glycosides, resins, oleo-resins, aromatic & volatile oils, neutral principles etc, a number of other compounds are also known to exists in plant flora which are responsible for curative action of the herbs, although are relatively less known compounds. Recently some light has been thrown on steroid like compounds present in number of medicinal herbs. Chemically the compounds are known as sterols and are considered to be derivatives of the steroids. They resemble in structure with steroids and modern clinical studies have supported their role as anti inflammatory and analgesic agents.
2Beta -sitosterol is the most commonly studied sterol compound isolated from number of medicinal herbs and it has shown effectiveness in reducing serum cholesterol levels. 3Modern studies have indicated the usefulness of beta-sitosterol in benign prostate hypertrophy and the compound has been detected in Serenoa Repens commonly known as Saw Palmetto. 4The medicinal herb has been traditionally used in treating prostate symptoms the clinical trials have shown promise in stages 1 & 2 in reducing difficulties associated with BPH but it has nothing to do with enlarged size of the gland. In addition the medicinal herb is known to contain sterols including beta sitosterol-3-o-glycosides, beta-sitisterol-3-o-glycosides, beta-sitosterol-fatty acid esters and their glycosides.
5,6,7 Disogenin is another compound present in number of herbs like Hedichyum spicatum, Trigonella foenum- graecum, Pueraria tuberosa & Dioscorea villosa. Oral contraceptives & sex hormones are derived from Disogenin. It is extracted from medicinal herbs as well as prepared commercially. Due to wide the distribution of the compound in above herbs, they have been used in various types of sexual disorders like impotency. 8Ruscogenins are other compounds present in Yucca liliaceae that are used in treating pain and inflammation of arthritis and rheumatism. Yucca filamentosa is other known species, which contains Ruscogenin as active principle. 9,10Ruscogenins are also present in Ruscus aculeatus and in animal tests; there was increase in venous tone and an electrolyte-like reaction on the cell wall of the capillaries.
Smilax officinalis is medicinal herb that is known to contain steroid like compounds-saponin glycosides and according to some researchers actually the herb contains male hormones. 11It also has been used in herbal medicine as an anti-inflammatory agent in curing arthritis and rheumatism. Rubus idaeus, commonly called as raspberry, is also known to contain such type of compounds.
12 Phyto-estrogens are group of pharmacologically active compounds present in Asparagus officinalis where they are known as Asparagosides A, B, D, F, G, H $I . Although the herb finds application in female sexual disorders but effectiveness for the claimed application has not been sufficiently documented. 13In Asparagus adscendens, active compounds are called Shatavarins 1-4 and in clinical studies they shown estrogen like activity. According to Mitchell Deborah these phyto-estrogens inhibit the conversion of testosterone to dihyrotestosterone, thereby increasing the count of testosterone in the body. Co- incidentally the role of the herb has been described in old texts of Ayurveda as sexual tonic. Coriander sativum [commonly known as fennel] also contains phyto- estrogens and has shown promise in treating premenstrual syndrome. Some glycosides on hydrolysis produce aglycones like gitogenin and tigogenin, which also are being used in steroid synthesis.
14 Balsamdendron commiphora mukul commonly known as Guggul contains special group of compounds called Guggulsterones, which range from E to Z. 15,16,17They are known as active principle of the herb and accounts for the use of the herb in hyperlipidemia and arthritis. 18Withania sominifera commonly known as Ashwagandha contain pharmacologically active compounds called Withanolides, which are considered to be responsible for various applications of the herb as adaptogen and immunomodulator. 19Withaferin-A is the most important group of Withanolide and has shown promise as potent anti cancer agent. 20The Withanolides are basically steriod lactones and various types have been isolated.
A special group of compounds called cardioactive steroids [better known as cardiac glycosides] deserves special mention. Digitalis purpurea, Stropanthus gratus and Urginea indica are reputed remedies as cardiac tonics. Clinically they find application in congestive cardiac failure. All of them contain steroid saponins as active constituents. 21Calotropis procera is known to contain cardioactive glycoside calotropine, which has shown an antitumor effect in vitro on human epidermiod carcinoma cells of the rhinopharynx. Besides it also acts as expectorant and diuretic.
In Homeopathic system of medicine, Convallaria majalis is a reputed remedy in various heart diseases. It also contains cardioactive steroid glycosides, which vary in the herb according to geographical source, and main active constituents are convalloside, convallatoxin and convallatoxol. In clinical studies they have shown positive inotropic effect on the myocardium and it lowers the elevated left ventricular pressure as well pathologically raised venous pressure.
Glycyrrhiza glabra works like steroids but without any side effects. The roots contain glycrrhizin and allied compounds. Research has indicated that it is anti inflammatory, hel;ps in biosynthesis of cholestrol and also promotes excretion of cholestrol.
From above it can be concluded that that sterol compounds are less known for their medicinal importance. Some of them have been isolated and researchers are studying hard to find their exact mode of action. In future a number of compounds can be expected from the sterols that can provide us with life saving drugs. The only need of the hour is to investigate the compounds with open mind so that maximum benefit can be withdrawn from them.
Monday, September 25, 2006
Distribution of Steroid like Compounds in Plant Flora