| Abstract
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Through bioactivity-directed fractionation, six cytotoxic constituents have been characterized from the bark of Plumeria rubra L. collected in Bandung, Java, Indonesia. Three iridoids, fulvoplumierin, allamcin, and allamandin, as well as 2,5-dimethoxy-p-benzoquinone, were found to be active constituents of the P. rubra petroleum ether- and chloroform-soluble extracts. Cytotoxic compounds isolated from the water-soluble extract of the bark were the iridoid, plumericin, and the lignan, liriodendrin. Five additional iridoids, 15-demethylplumieride, plumieride, usd\alphausd-allamcidin, usd\betausd-allamcidin, 13-O-trans-p-coumaroyplumieride and the flavonoid glycoside, plumerubroside, were obtained as inactive constituents. Plumerubroside was found to be novel naturally occurring gallocatechin type flavan-3-ol glycoside to have been characterized. Five cytotoxic constituents have been isolated from the roots of Eurycoma longifolia Jack, collected in Samarinda, Indonesia. For canthin-6-one alkaloids, namely, 9-methoxycanthin-6-one, 9-methoxycanthin-6-one-N-oxide, 9-hydroxycanthin-6-one, 9-hydroxy-canthin-6-one-N-oxide, and one quassinoid, eurycomanone, were found to be cytotoxic principles. Two additional isolates, usd\betausd-carboline-1-propionic acid and 7-methoxy-usd\betausd-carboline-1-propionic acid were not significantly active against these cultured cells. However, eurycomanone and 7-methoxy-usd\betausd-carboline-1-propionic acid were found to demonstrate significant antimalarial activity as judged by studies conducted with cultured Plasmodium falciparum strains. 9-Methoxycanthin-6-one-N-oxide,9-hydroxycanthin-6-one,9-hydroxycanthin-6-one-N-oxide and 7-methoxy-usd\betausd-carboline-1-propionic acid were established as being novel compounds. The structures of the isolates from P. rubra and E. longifolia were identified or elucidated through the use of some modern nmr technique, in addition to chemical methods.
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