CHEMICAL STUDIES ON MEDICINAL PLANTS FROM CONVOLVULACEAE, EUPHORBIACEAE AND BRASSICACEAE FAMILIES

Abstract

The isolation and examination of natural products from the plants have drawn the attention of chemists and pharmacologists from the very early days. Natural products, the secondary metabolic products of plants, include many classes of organic compounds like alkaloids, steroids, terpenoids, flavonoids, coumarins etc. The knowledge of chemical constituents of plants is needed for the discovery of new therapeutic agents and for obtaining valuable information in regard to new sources of economic materials and novel chemical structures often leading the chemists to modified semisynthetic compounds. A knowledge of plant constituents is also valuable in the area of chemotaxonomy and biosynthesis. Indian medicinal Plants have been the basis of the Ayurvedic and Unani systems of medicine and are extensively used by the folk. In view of the information gathered from the local people and the subsequent literature survey on a large number of plants, it was found that certain species of Gonvolvulaceae,Euphorbiaceae and Brassicaceae are medicinally important. Moreover there are a number of: Plant species of these families on which either a very little or no chemical work has been done. Thus, chemical .. 11 examination of four local plant species namely Bvolvulus nummularius Linn (Convolvulaceae), Bisckofia .iavanioa Blume (Euphorbiaceae), Poinsettia pulcherrima Wind (Euphorbiaceae) and Arabidopsis thaliana (L) Heynh (Brassicaceae) was undertaken. The thesis begins v/ith an introduction to the topic giving a brief account of the importance of plant chemistry, a review of medicinal importance and chemical work done on some important plants of Convolvulaceae, Euphorbiaceae and Brassicaceae families. Bvolvulus nummularius Linn, often used in neuralgia* helmintis, liver disorders and abdominal pains, was extracted with petroleum ether and ethanol successively. The petroleum ether extract on chromatography over silica gel afforded three compounds identified as triacontane, hentriacontane and p-sitosterol. The ethanolic extract was extracted with petroleum ether, ethylacetate and n-butanol successively. The latter two extracts were combined and resolved into ether soluble and methanol soluble portions. The ether soluble portion on chromatographic separations yielded luteolin and 3',4',5',7-tetrahydroxyflavone the occurrence of which in nature has been reported for the first time. The methanol soluble portion furnished two new glycosides namely Ill 3',4',5*,7-tetrahydroxyflavone~7-0-rhamnoside, designated as evolvuside A and 3',4',5',7-tetrahydroxyflavone-7-0- glucoside, designated as evolvuside B. The leaves of Bischofia ,javanica Blume which is used in helmintis, dysentry and sores were extracted with Petroleum ether, benzene and ethanol successively. The petroleum ether extract was fractionated into methanol insoluble and methanol soluble portions. Methanol insoluble portion on column chromatography on silica gel afforded triacontane while the methanol soluble portion gave three compounds identified as p-amyrin, friedelin and p-sitosterol. The benzene extract was chromatographed to obtain friedelin, P-sitosterol and ursolic acid. The ethanolic extract was dissolved in water and extracted with petroleum ether, ethylacetate and n-butanol. The ethylacetate extract was resolved into chloroform and methanol soluble parts. The chloroform soluble part on chromatography afforded chrysoeriol, fisetin and quercetin while the methanol soluble portion yielded two glycosides which were characterized as luteolin-5-0-glucoside and quercitrin. The dried and powdered leaves of Poinsettia pulcherrima Wind were extracted with petroleum ether and ethanol successively. The petroleum ether extract on .. iv chromatography over silica gel afforded octacosanol, octacosanoic acid, lupeol acetate and 0-sitosterol. The ethanolic extract was further fractionated, with petroleum ether, ethylacetate and n-butanol. The latter two fractions were combined and resolved into chloroform soluble and methanol soluble portions. The chloroform soluble fraction on chromatographic separation afforded 3,4'-dimethylquercetin and quercetin, while the methanol soluble portion yielded fisetin-3-0-glucoside, kaempferol-3-0-rutinoside and rutin. The chemical investigation of fresh fruits of Poinsettia pulcherrima led to the isolation of epigermanicyl acetate, germanicyl acetate, octacosanol, germanicol andp-sitosterol. Arabidopsis thaliana (l) Heynh., which is uecid in curing viral fevers and sores, was collected in the month of March. The dried and powdered Plant material was extracted with petroleum ether, benzene and ethanol. The petroleum ether and benzene extracts on chromatography gave octacosane, triacontanol and p-sitosteroi. The ethanolic extract was repeatedly extracted with petroleum ether, ethylacetate and n-butanol. The latter two extracts were combined and resolved into chloroform soluble and methanol soluble portions. The chloroform extract on chromatographic separation yielded 3,4'-dimethylkaempferoi, and apigenin, . • V while the methanol soluble portion afforded kaempferol and kaempferol-3-0-glucoside. The isolated compounds were characterized by spectroscopic methods such as IR,UV,MH and MS. Chemical methods such as degradation, hydrolysis, methylation, acetylation were also used for structural elucidation. Wherever possible, the known compounds were compared with authentic samples.