Picrasma javanica Bl., a medicinal plant used for the treatment of malaria in traditional medicine was evaluated for antimalarial activity. Primary screening demonstrated that the chloroform extract of the bark possessed the highest yield of antimalarial activity. Chemical isolation and purification of the active alkaloidal part yielded three different pure alkaloid components. Among these, one component was identified as the known major bark alkaloid, 4-methoxy-l-vinyl-fi-carboline, and a second new alkaloid, 6-hydroxy-4-methoxy-l-vinyl-fi-carboline. Complete characterization of the remaining alkaloid was not possible due to its inferior yield. The two identified alkaloids showed in vitro antimalarial activity against multi-drug resistant Thai isolates of Plasmodium falcipamm.

Preparations from the plant Celartrus paniculatus Willd. have been used for treatment of malaria and other febrile illness in the traditional medicine practices of Thailand. Crude solvent extracts from the root bark and stem of C. paniculatus were screened for antimalarial activity against P . falcipamm using an in vitro culture system. A fraction of the chloroform extract of the root bark showed the bighest antimalarial activity. An active principle was isolated and characterized from the chbloroform fraction and identified as a quinonoid triterpene, pristimerin. Wben tested in vitro against various multidrug resistant isolates of P . falcipamm, pristimerin was less active than the conventional antimalarial drugs tested.

The medicinal plant, Brucea javanica (L.) Merr.(Simaroubaceae) was examined for antimalarial properties. Among different crude solvent extracts of the fruit, the chloroform extract was shown to have the most potent in vitro antimalarial activity. Three active compounds were isolated and purified from the chloroform extract. These compounds were confirmed as bruceine A, bruceine B hydrate and bruceine C by UV, IR, NMR and mass spectra. When tested in vitro against multi-drug resistant isolates of P. falciparum bruceine A and bruceine B hydrate were similar in activity (1D50 of 8.66 and 8.15 nglml) whereas bruceine C had an 1D50 of 1.95 ng/ml. These compounds were comparable in in vitro activity to the new antimalarial drug, mefloquine (1D50 of 6.26 ng/ml).

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