Cleistopholis patens (Benth.) Engl. and Diels (Annonaceae) is a large tree found throughout West Africa. Two previous studies on the stem and root bark have resulted in the isolation of sesquiterpenes and alkaloids (1,2). Alcoholic extracts of the root bark of C. patens showed significant anticandidal activity. As a part of our continuing search for new anticandidal drugs from natural sources, we report herein our results on the bioassay directed isolation of the active anticandidal component of C. patens. The dried, ground root bark was extracted by percolation with n-hexane (inactive) and then with 95% EtOH. The active alcoholic extract was partitioned between CHCl3 and H2O. The active CHCl3 extract was chromatographed over silicic acid using CHCl3 and a stepwise gradient of increasing percentage of MeOH/CHCl3 as eluent. Fractions were pooled on the basis of tlc analysis. The anticandidal activity was concentrated in a fraction (500 mg) that was eluted with 5% MeOH in CHCl3. Further purification of this fraction over neutral alumina using EtOAc/n-hexane as eluting solvent resulted in the isolation of the active component as a yellow crystalline material having mp 153-155". This substance was identified as the previously reported alkaloid, eupolauridine [1] (2-4), by comparison with an authentic reference sample. Eupolauridine [1] exhibited a significant zone of inhibition against three test strains of C. albicans. The minimum inhibitory concentration (MIC) of eupolauridine was found to be 1.56 pg/ml for each of the three strains in yeast-nitrogen broth. By comparison, the MIC value of amphotericin B, the current drug of choice for disseminated candidiasis, is 0.39 pg/ml. Consequently, eupolauridine was considered a promising potential new antifungal drug. Because only small amounts were isolated and much larger quantities are necessary for in vivo evaluation, eupolauridine [1] was prepared by synthesis as previously reported (3). All of the synthetic intermediates were also evaluated for anticandidal activity. One of the intermediates [2] was also shown to be active against Candida. This intermediate is also the known alkaloid onychine, which has been reported from C. patens (2) and originally reported from Onychopetalum amazonirum (5). The original structure reported for onychine [3] (5) and reported in C. patens (2) and elsewhere (6) has been shown to be incorrect (7,8); the correct structure is represented by 2. While the structure reported for onychine [2] (7,8) appears to be based on solid chemical evidence, a COSY spectrum of dihydroonychine [4] (2,5) clearly showed long-range couplings between H-9 and the protons of the methyl group independently confirming structure 2 for onychine. The physical and spectroscopic data reported for 1 and 2 (2,6,7) agree well with the data obtained here except for the 13C-nmr assignments for onychine [2]. The 1H-nmr assignments (2,6) were confirmed by examining the COSY spectrum of 2. The 13C-nmr assignments reported here (see Experimental section) differ significantly with those reported previously (2) and were established by utilizing 1H-13C heteronuclear correlations and by examining the proton-coupled data. The quaternary center assignments (1, 4a, 4b, 8a, 9a) were confirmed by utilizing selective low power decoupling techniques (irradiation at H for H-2, H-3, H-5, H-6, H-7, H-8, and CH3). Onychine is comparable to eupolauridine in its anticandidal activity with an MIC value of 3.12 pg/ml against C. albicans B3 11 in yeast-nitrogen broth. Therefore, onychine is also considered a potential candidate for further development. Studies are currently in progress to evaluate the in vivo efficacy and toxicity of eupolauridine and onychine, and those results will be reported elsewhere.