Lalith Jayasinghe

Antifungal constituents of the stem bark of Bridelia retusa

Antifungal activity guided fractionation of solvent extracts of the stem bark of Bridelia retusa of the family Euphorbiaceae against Cladosporium cladosporioides, furnished new bisabolane sesquiterpenes, (E)-4-(1,5-dimethyl-3-oxo-1-hexenyl)benzoic acid, (E)-4-(1,5-dimethyl-3-oxo-1,4-hexadienyl) benzoic acid, (R)-4-(1,5-dimethyl-3-oxo-4-hexenyl)benzoic acid and (-)-isochaminic acid, together with the known (R)-4-(1,5-dimethyl-3-oxohexyl)benzoic acid (ar-todomatuic acid), 5-allyl-1,2,3-trimethoxybenzene (elemicin), (+)-sesamin and 4-isopropylbenzoic acid (cumic acid). All these compounds showed fungicidal activity on TLC bioautography method at very low concentrations except elemicin.

Ecdysterone from stem of Diploclisia glaucescens

Abstract The stem of Diploclisia glaucescens afforded ecdysterone in a high yield of over 3%. 13 C NMR of the tetraacetate and NOE studies on the triacetate provided further data on the structure and conformation of this phytoecdysteroid. Hemolytic, insecticidal and spermicidal activity are reported for the compound.

Triterpenoids from Anamirta cocculus

Abstract One new triterpenoid, 2α,3β,23-trihydroxy-11α,12α-epoxyolean-28,13β-olide and two new triterpenoid glycosides, β- d -glucopyranosyl-2β,3β,23-trihydroxyolean-12-en-28-oate and 2α,3β-dihydroxy-23- β- d -glucopyranosyloxyolean-12-en-28-oic acid, are reported from the stem of Anamirta cocculus. The major compounds isolated are the already known 2α,3β,23-trihydroxyolean- 12-en-28-oic acid (arjunolic acid) and its 28-O-β- d -glucopyranoside. None of the isolated compounds showed any molluscicidal or antifungal activity.

Hederagenin glycosides from Pometia eximia

Seven new saponins, all glycosides of hederagenin (3 beta,23- dihydroxyolean-12-en-28-oic acid), were isolated from the stem of Pometia eximia along with hederagenin and two known saponins. Their structures were established as 28-O-beta-D-apiosyl(1-->2)-beta-D-glucopyranosyl-, 3-O-alpha-L- arabinofuranosyl(1-->3)[alpha-L-rhamnopyranosyl (1-->2)]-beta-D- xylopyranosyl-, 3-O-beta-D-apiosyl(1-->3)[alpha-L-rhamnopyranosyl-(1-->2)-beta-D- glucopyranosyl-, 3-O-alpha-L-arabinofuranosyl(1-->3)[alpha-L-rhamnopyranosyl- (1-->2)]-beta-L-arabinopyranosyl-, 3-O-beta-D-xylopyranosyl(1-->3)[alpha-L- rhamnopyranosyl(1-->2)]-alpha-L-arabinopyranosyl-, 3-O-beta-D-xylopyranosyl-(1-->3)[alpha-L-rhamnopyranosyl(1-->2)]-beta-D- glucopyranosyl-, 3-O-beta-D-galactopyranosyl(1-->3)[alpha-L-rhamnopyranosyl(1-->2)]-beta- D- glucopyranosyl-hederagenins.

Alkaloids of Uncaria elliptica

Abstract Ajmalicine, formosanine, isomitraphylline and mitraphylline have been isolated from the bark of Uncaria elliptica . Differences in alkaloid content within the species have been observed.

Diploclisin, a bidesmosidic triterpenoid saponin from Diploclisia glaucescens

Abstract The mature stem of Diploclisia glaucescens furnished diploclisin, a new bidesmosidic saponin. The structure of diploclisin was established by chemical and spectroscopic methods as β- d -glucopyranosyl 3β-(β- d -glucopyranosyloxy)-23-hydroxy-30-carbomethoxyolean- 12-en-28-oate.

3-Deoxy-1β,20-dihydroxyecdysone from the leaves of Diploclisia glaucescens

Chemical investigation of methanol extract of the leaves of Diploclisia glaucescens of the family Menispermaceae furnished a new ecdysteroid, 3-deoxy-1beta,20-dihydroxyecdysone. The structure of the new ecdysteroid was established on detailed analysis of spectral data. The 3-deoxy ecdysteroid showed 40% potency of 20-hydroxyecdysone in the spiracle index assay using the fourth instar larvae of the silkworm Bombyx mori.

Ursene carboxylic acids of Uncaria elliptica

The structures of three triterpenoid acids isolated from Uncaria elliptica have been revised following a spectroscopic analysis of the major acid, uncaric acid.