Subramaniam Sotheeswaran

Canaliculatol, an antifungal resveratrol trimer from Stemonoporous canaliculatus

Abstract A new resveratrol trimer, canaliculatol, has been isolated from the bark of Stemonoporus canaliculatus . Canaliculatol showed antifungal activity against the fungus, Cladosporium cladosporioides. The structure and stereochemistry of canaliculatol is reported in this paper.

Triterpenoids and coumarins from the leaves of calophyllum cordato-oblongum

Abstract The hot light petrol extractives of the leaves of Calophyllum cordato-oblongum gave D:A-friedo-oleanan-3-one, 28-hydroxy-D:A-friedo-oleanan-3-one (canophyllol) and three new coumarins: cordatolides A and B and oblongulide.

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.

Terpenoid and biflavonoid constituents of Calophyllum calaba and Garcinia spicata from Sri Lanka

Abstract A new bark acid, isochapelieric acid (cis-chapelieric acid), chapelieric acid, friedelin, friedelan-3β-ol, canophyllal, canophyllol, friedelan-3β,28-diol, canophyllic acid and amentoflavone have been isolated and characterized from leaf extractives of Calophyllum calaba. 13CNMR spectra of methyl chapelierate and methyl isochapelierate have been recorded and interpreted. Leaf extractives of Garcinia spicata afforded an unidentified long chain carboxylic acid, friedelin, friedelan-3β-ol, sitosterol and the biflavanones GB-1, GB-1a, GB-2a and morelloflavone. Chemotaxonomic significance of the occurrence of some of the above foliar constituents in Calophyllum and Garcinia species is discussed.

Polyphenols from Stemonoporus species

Abstract Methanol extracts of the bark of six Stemonoporus species have been investigated. A new polyphenol, stemonoporol, has been isolated from four species. The polyphenols, copalliferol A and vaticaffinol are reported for the second time. Formic acid treatment converted stemonoporol to copalliferol A.

Minor xanthones of Hypericum mysorense

Abstract 2-Hydroxyxanthone, 1,7-dihydroxyxanthone, 1-hydroxy-7-methoxyxanthone, 6,7-dimethoxy-1-hydroxyxanthone and a new natural product, 2-hydroxy-3-methoxyxanthone, have been isolated and characterized from the phenolic fraction of the chloroform extract of the timber of Hypericum mysorense . The presence of simple xanthones in this genus supports the classification of Hypericum in the subfamily Hypericoideae in Guttiferae.

Horsfieldin, a lignan and other constituents from Horsfieldia iryaghedhi

Abstract A new lignan, horsfieldin [2-(3-hydroxy-4-methoxyphenyl)-6-(3,4-methylenedioxyphenyl)-3,7-dioxabicyclo(3,3,0)octane], d -asarinin, (−)-dihydrocubebin, dodecanoylphloroglucinol, myristic acid, trimyristin and sitosterol have been isolated and characterized from the hot methanol extract of Horsfieldia iryaghedhi seeds. The absolute configuration of the lignans and the chemotaxonomic significance of their occurrence is discussed.

Calocalabaxanthone, the putative isoprenyl precursor of calabaxanthone from Calophyllum calaba

Abstract The bark of Calophyllum calaba var. calaba contains a new xanthone, 2,8-di-(3-methylbut-2-enyl)-1,3-dihydroxy-7-methoxyxanthone (calocalabaxanthone), the precursor of 5-hydroxy-8-methoxy-2,2-dimethyl-7-(3-methylbut-2-enyl)-2H,6H-pyano-(3,2-b)-xanthen-6-one (calabaxanthone). In addition the bark contains calabaxthone and the other constituents isolated earlier from Calophyllum calaba var. worthingtonii .

3,5,7,3′,5′-Pentahydroxyflavan and 3α-methoxyfriedelan from Humboldtia laurifolia

Abstract The leaf, bark and timber extractives of Humboldtia laurifolia were investigated and the following compounds have been isolated: O -acetyloleanolic aldehyde, a sitosteryl ester, lupeol, sitosterol, a fatty acid, 5,7,4′-trihydroxyflavone (apigenin), (2 R ,3 R )-3,5,7,3′,5′-pentahydroxyflavan and 3α-methoxyfriedelan. The latter two compounds are new natural products.

(-)-5-Methylmellein and catechol derivatives from four Semecarpus species

Abstract Four Semecarpus species endemic to Sri Lanka, S. gardneri , S. obscura , S. subpeltata and S. walkeri , were investigated. The fruits of these species are rich in 3-alk(en)yl-catechols and the timber extractives of three species contained (−)-5-methylmellein.