Showing papers by "John H. Cardellina published in 1998"

HIV-inhibitory and cytotoxic oligostilbenes from the leaves of Hopea malibato.

Abstract: Three new oligostilbenes, malibatols A (1) and B (2) and dibalanocarpol (3), together with one known oligostilbene balanocarpol (4), were isolated from the organic extract of the leaves of Hopea malibato. The structure elucidation of these compounds was based on the interpretation of their chemical and spectral data. Compounds 3 and 4 exhibited very modest HIV-inhibitory activity, while compounds 1 and 2 were cytotoxic to the host cells (CEM SS) in the antiviral assay.

Structure-activity requirements for flavone cytotoxicity and binding to tubulin

Abstract: A series of 79 flavones related to centaureidin (3,6,4‘-trimethoxy-5,7,3‘-trihydroxyflavone, 1) was screened for cytotoxicity in the NCI in vitro 60-cell line human tumor screen. The resulting cytotoxicity profiles of these flavones were compared for degree of similarity to the profile of 1. Selected compounds were further evaluated with in vitro assays of tubulin polymerization and [3H]colchicine binding to tubulin. Maximum potencies for tubulin interaction and production of differential cytotoxicity profiles characteristic of 1 were observed only with compounds containing hydroxyl substituents at C-3‘ and C-5 and methoxyl groups at C-3 and C-4‘.

Pyranocoumarins from tropical species of the genus Calophyllum: a chemotaxonomic study of extracts in the National Cancer Institute collection.

Abstract: (+)-Calanolide A, a novel dipyranocoumarin from the Malesian tree Calophyllum lanigerum var. austrocoriaceum, and a closely related compound, (-)-calanolide B, isolated from Calophyllum teysmannii var. inophylloide, are representatives of a distinct class of nonnucleoside HIV-1 specific reverse-transcriptase inhibitor under development as an AIDS chemotherapeutic. NCI repository specimens totalling 315 organic extracts from 31 taxa of Calophyllum were analyzed for related pyranocoumarins using a simple TLC system. A total of 127 extracts was initially classified as "positive"; eight out of the 31 taxa examined, representing perhaps 28 species already described (1/7-1/8 of all the species in this genus), contained prenylated coumarins, suggesting that these compounds, while sometimes abundantly present, are not widespread in the genus. Representative members of the TLC-positive extracts were partitioned between CH2C12 and 25% aqueous MeOH; the CH2C12-soluble materials were then analyzed by TLC and 1H NMR to confirm the presence of pyranocoumarins. The anti-HIV activity of the partitioned extracts are also presented. This study suggested that there are several distinctive coumarin chemotaxonomic markers distinguishing species of this genus.

The Lobatamides, Novel Cytotoxic Macrolides from Southwestern Pacific Tunicates†

Abstract: Novel macrolides, lobatamides A-F (1-6), have been isolated from shallow water Australian collections of Aplidium lobatum, from a deep water collection of Aplidium sp., and from an unidentified Philippine ascidian. Full details of the isolation and structure elucidation of 1-6 are provided herein, along with results and analyses of the testing of lobatamides A-D (1-4) in the NCI human tumor 60 cell-line screen. The lobatamides share a common core structure with the recently described salicylihalamides, which were isolated from a Haliclona sp. sponge. COMPARE analyses of the mean-graph differential cytotoxicity profiles of the lobatamides and the salicylihalamides showed high correlations with each other but not with members of the NCI's standard agents database. These compounds, therefore, appear to comprise a new mechanistic class, meriting further antitumor investigations.

(-)-Frondosins A and D, HIV-Inhibitory Sesquiterpene Hydroquinone Derivatives from Euryspongia sp

Abstract: (-)-Frondosins A and D, two sesquiterpene hydroquinone metabolites, were isolated and identified from the HIV-inhibitory organic extracts of the marine sponge Euryspongia sp. In contrast to the dec...