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The crude methanol extract of the stem wood of Quassia amara L. inhibited both the basal and LH-stimulated testosterone secretion of rat Leydig cells in a dose-dependent fashion. Fractionation of the extract by chromatography gave quassin (1) and 2-methoxycanthin-6-one (2); compound 1 proved to be the bioactive agent.

After removing lipophilic material, the ground root bark of Quassia africana Baill. (Simaroubaceae) was extracted with ethanol 95 %. Partitioning between chloroform, ethyl acetate and water yielded three crude extracts. Pronounced activities were shown by the chloroform and ethyl acetate crude extracts against Herpes simplex, Semliki forest, Coxsackie and Vesicular stomatitis viruses. By repeated column chromatography and preparative thin layer chromatography on silica gel, two quassinoids, i. e., quassin and simalikalactone D were isolated. Structures of the pure compounds were established primarily using NMR spectroscopy. Mass spectral information confirmed the assigned structures. Simalikalactone D was responsible, at least in part, for the high antiviral activity observed for the chloroform crude extract. Quassin showed no activity. For quassinoids the ester group at C-15 and the epoxymethano bridge between C-8 and C-13 appeared to be important structural features in order to exhibit a pronounced antiviral activity.

A microdilution technique was developed for the assessment of in vitro cytotoxicity against KB cells derived from a human epidermoid carcinoma of the nasopharynx. The test was used to determine the cytotoxicity of a series of quassinoids, isolated from Brucea javanica, and which have previously been shown to demonstrate activity against Plasmodium falciparum. The 50% effective dose (ED50) for 7 quassinoids tested against KB ranged from 0.008 microgram/ml for bruceantin, the most cytotoxic of the compounds tested to greater than 5 micrograms/ml for bruceolide, the least toxic tested. The activities of the quassinoids against KB did not parallel the known activities of the quassinoids against Plasmodium falciparum suggesting that the quassinoid mode of antimalarial action is not a simple cytotoxic effect and lends support to further investigation of the structure activity relationships within this group of compounds.

Three quassinoids from the roots of Eurycoma longifolia Jack were evaluated for antimalarial activity against nine Plasmodium falciparum isolates obtained from patients infected with chloroquine-resistant malaria. The results indicated that eurycomanol, eurycomanol 2-O-beta-D-glucopyranoside, and 13 beta, 18-dihydroeurycomanol possessed antimalarial activity with IC50 values of 1.231-4.899 microM, 0.389-3.498 microM, and 0.504-2.343 microM, respectively, compared with 0.323-0.774 microM for chloroquine.

Inhibition of the uptake of 3 H-thymidine into TLX-5 mouse lymphoma cells has been used to assess the cytotoxicity of extracts and fractions of BRUCEA JAVANICA. Six bruceolides, two dehydrobruceolides and a dihydrobruceolide have been isolated from roots, fruits and stems. Bruceine A was the major bruceolide of the roots and of the fruits. The potent antineoplastic bruceolides, bruceantin and bruceantinol, previously isolated from B. ANTIDYSENTERICA and B. GUINEENSIS have been isolated together with the novel compounds dehydrobruceine A and dihydrobruceine A. Bruceantarin and dehydrobruceine B, not previously reported from this species, and bruceines B and C were also isolated. The identification of these nine compounds by means of their UV, EIMS, CIMS, FDMS and 1 H NMR spectra is discussed.