B. M. Ratnayake Bandara

Antimicrobial alkaloids from Zanthoxylum tetraspermum and caudatum.

Two benzophenanthrene alkaloids, 8-acetonyldihydronitidine and 8-acetonyldihydroavicine were isolated from Zanthoxylum tetraspermum stem bark along with liriodenine, sesamin, lichexanthone and (+)-piperitol-gamma,gamma-dimethylallylether. The species endemic to Sri Lanka, Z. caudatum, contained sesamin, savinin, liriodenine, decarine and 8-O-desmethyl-N-nornitidine. 8-Acetonyldihydronitidine and 8-acetonyldihydroavicine showed significant antibacterial activity while the former along with liriodenine was strongly antifungal. Savinin exhibited potent spermicidal activity. Both savinin and sesamin exhibited significant insecticidal activity.

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.

An antifungal constituent from the stem bark of Butea monosperma

The petroleum and ethyl acetate extracts of the stem bark from Butea monosperma displayed antifungal activity against Cladosporium cladosporioides. The active constituent of low polarity was isolated by bioassay-monitored chromatographic fractionation, and identified as (-)-medicarpin by comparison of physical data. The antifungal activity of (-)-medicarpin was found to be greater than that of Benlate, a standard fungicide, while (-)-medicarpin acetate also exhibited significant activity against C. cladosporiodes.

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.

Two chemically distinct groups of calophyllum species from Sri Lanka

Abstract The leaf extracts of Calophyllum moonii and C. walkeri were investigated. The former contained neoflavonoids whereas the latter had calozeylanic acid. Distribution of natural products in the leaf extracts of seven Calophyllum species has been reviewed and the existence of two chemically distinct groups in Calophyllum species has been recognized.

Acridone alkaloids and coumarins from Pleiospermium alatum.

Abstract The root bark of Pleiospermium alatum afforded five alkaloids, five coumarins, lupeol and stigmasterol. One of the acridones, 1,5,6-trihydroxy-2,3-dimethoxy-10-methyl-9-acridone is a new compound while another, 1-hydroxy-2,3,5,6-tetramethoxy-10-methyl-9-acridone, is a new natural product. Chemotaxonomic aspects of the occurrence of acridone and coumarins in Pleiospermium is discussed. Seselin, one of the coumarins encountered displayed significant antifungal activity against Cladosporium cladosporioides .

An antifungal chromene from Eupatorium riparium

Abstract Methylripariochromene A (6-acetyl-7,8-dimethoxy-2,2-dimethylchromene), a root constituent of Eupatorium riparium , displayed antifungal activity against five of the seven fungal species tested. The chromene showed a toxicity to the fungus Colletotrichum gloeosporioides , a tropical pathogen, comparable to that of a commercial fungicide, although the chromene appeared to be fungistatic.

Ent-kauranes and oleananes from Croton lacciferus

Abstract The roots of Croton lacciferus furnished three ent -kauranoids, two of which are new natural products, and two oleananes. Two of the kauranoids showed moderate insecticidal activity against Aphis craccivora .

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.

Diterpene alcohols from Croton lacciferus

Abstract The roots of Croton lacciferus afrorded a novel ent -kauranoid and three other ent -kauranoid alcohols, one of which is a new natural product, together with 2,6-dimethoxybenzoquinone. The benzoquinone displayed antifungal activity against Cladosporium cladosporioides