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Purpose: In a continuation of our search for novel antifungal compounds from higher plants, the standard extract of the bark of Pithecellobium racemosum was found to have good activity against important AIDS-related opportunistic yeasts., Methods: The extract was subjected to bioguided fractionation using silica gel column chromatography which led to purification of triterpene glycosides. The structures of these compounds were determined by a combination of spectroscopic (IR, NMR, HRMS) and chemical methods., Results: Compound 1 is a new glycoside, 3-O[alpha-L-arabinopyranosyl (1-2)][alpha-L arabinopyranosyl (1-6)]2-acetoamido-2-deoxy-beta-D-glucopyranosyl oleanolic acid and Compound 2 was identified as the known compound 3-O-[alpha-L-arabinopyranosyl (1-2)]alpha-L-arabinopyranosyl (1-6)] 2-acetamido-2-deoxy-beta-D-glucopyranosyl echinocystic acid., Conclusions: Compound 1 is a new glycoside, 3-O-[alpha-L-arabinopyranosyl (1-2)]alpha-L-arabinopyranosyl (1-6)]-2-acetoamido-2-deoxy-beta-D-glucopyranosyl oleanolic acid and exhibits moderate antifungal activity against T. mentogrophytes, C. albicans and S. cerevisiae with MIC values of 6.25, 12.5 and 12.5 micrograms/ml respectively.

Purpose: Deoxoartemisinin is a semisynthetic antimalarial with potential for treatment of multiple drug resistant malaria. Metabolism studies were conducted to aid in future drug development., Methods: Microbial model systems were employed which have been shown to be good predictors of mammalian drug metabolites. Metabolism studies using rats were also performed., Results: Three microbial metabolites of deoxoartemisinin were identified (2, 3, and 4). Metabolite 3 was also found in rat plasma. HPLC/MS analyses were performed on the rat plasma using 2, 3, and 4 as standards. All metabolites were thoroughly characterized by 1H and 13C-NMR. An additional rat plasma metabolite was revealed and it was shown not to be 9 alpha-hydroxyartemisinin., Conclusions: Deoxoartemisinin was metabolized to three microbial metabolites. Metabolism by rats showed the presence of two metabolites in the plasma, one of which was the same as the microbial metabolite.

In simulated stomach acid (aqueous 0.01 M HCl, 37 degrees C) beta-arteether decomposed (half-life, 441 +/- 17 min) to dihydroartemisinin, which subsequently rearranged to a new compound (1) having an endoperoxide group and an aldehyde group. The in vitro antimalarial activity of dihydroartemisinin is similar to that of beta-arteether, whereas compound 1 had approximately 1/10th the activity of beta-arteether. Compound 1 was prepared in sufficient quantities to afford samples for biological evaluation and a complete chemical characterization with 1H- and 13C-NMR and mass spectrometry. While beta-arteether would be somewhat unstable in the stomach, if the drug were administered on an empty stomach (emptying time, approximately 30 min) as a suspension or tablet, sufficient quantities of intact arteether may reach the small intestines, where it would be stable and readily absorbed. Its decomposition products, dihydroartemisinin and 1, may also contribute to the antimalarial activity of the administered drug following oral administration.

Drummondin C (1) is an antibiotic isolated from a bioassay-directed fractionation of Hypericum drummondii (Grev. & Hook.)T.&G. It showed significant activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis and the acid-fast bacterium Mycobacterium smegmatis. Two structural units of drummondin C, the 8-acetyl-5,7-dihydroxy-2,2-dimethylchromene (6) and 5-acetyl-3-methyl-filicinic acid (9), were synthesized to determine the relative importance of the two substructure portions to the antibiotic activity of the compound. The low antimicrobial activity of 6 and 9 demonstrates the necessity of both units for the antibiotic activity of drummondin C.

The substitution of two deuterium atoms on the alpha-carbon of the primaquine side chain was found to produce a sevenfold decrease in the rate of conversion of primaquine to carboxyprimaquine by enzymatic oxidative deamination, but the deuterium substitution was found to have no significant effect on the in vitro antimalarial activity or on in vitro hepatocyte toxicity. Placing a single methyl group on the alpha-carbon was found to produce only a slight decrease in the rate of oxidative deamination. Although metabolic attack occurred adjacent to either the aniline nitrogen or the aliphatic amine, metabolic attack occurred primarily adjacent to the more basic nitrogen at the 1'-position, even when this position bore a methyl substituent. Primaquine, the alpha-dideutero analogue, and the alpha-methyl analogue were all found to have about the same in vitro antimalarial activity as determined in the liver hepatocyte assay.

Primaquine (I), a 6-methoxy-8-aminoqumoline derivative used for the treatment of malaria has previously been shown to be metabolized to 8-(3-carboxy-l-methyl-propylamino)-6-methoxyquinoline by both micro-organisms and laboratory rats. Reported herein is the synthesis of this novel metabolite.

Following the administration of primaquine diphosphate (20 mg/kg IP), six metabolites of primaquine were found in the bile of rats. Quantitative HPLC of the metabolites revealed that the sum of the six metabolites excreted in the bile represented a quantitative recovery of the dose of primaquine.

Rhesus monkeys were administered primaquine diphosphate (6.0 to 10.5 mg/kg, I.V.), and plasma samples were analyzed by high performance liquid chromatography for the presence of the unchanged drug and the major metabolite , 8-(3-carboxy-l-methylpropylamino)-6-methoxyquinoline (II). Primaquine had an unusually high affinity for tissue compartments which produced a rapid initial drop in plasma concentration. Within 15 minutes, the plasma concentration of II far exceeded that of primaquine. 35 to 83 % of the primaquine dose was converted to II; moreover, metabolite II possessed much lower affinity for the tissue compartments than primaquine itself.

Investigation of derivatization of primaquine (1) with various perfluoroacylating reagents revealed that the quinoline ring portion of the drug undergoes unexpectedly facile acylation. Chemical and spectral evidence in support of the assigned structures is presented and discussed. Results of the evaluation of these new primaquine derivatives for antimalarial activity is reported.

Primaquine, an 8-aminoquinoline antimalarial, is shown to undergo unexpectedly rapid aromatic proton exchange with the medium. At a pH less than 4, the exchange of C-5 is so fast as to be unmeasurable by proton nmr methods. At a pH of 6-6.5 the half-time for exchange is 4 to 5 minutes. This unexpectedly high rate of exchange of a carbon-proton with medium may provide an important clue to the biological activity of primaquine.

Following the synthesis of reference standards of the primaquine metabolites, a high-performance liquid chromatographic (HPLC) analytical method for carboxyprimaquine, its glycine conjugate, and its glucuronide conjugate in urine samples was developed. After the administration of primaquine, only trace quantities of primaquine and carboxyprimaquine (each less than 1% of dose) and no significant quantity of the two conjugates of carboxyprimaquine were excreted in the urine. When carboxyprimaquine was administered, only 0.3% of the dose was excreted in the urine. When carboxyprimaquine glycinate was administered, the compound was found in the 700- to 1300-µg/ml concentration range in the urine within the first few hours. Using (14)C-labeled primaquine, six new metabolites were found in the urine and partially characterized. The purported metabolites of primaquine (8-amino-6-methoxyquinoline, 5-hydroxyprimaquine, and 6-desmethyl-5-hydroxyprimaquine) were not found in the urine. A field screening test for the quantitation of primaquine metabolites in urine was also investigated. The inexpensive, but sensitive assay was found to give results that closely paralleled the more complex HPLC method and it was moderately well correlated with the total radioactivity in the urine samples.

Several 6-chloro-5-nitropyrimidines were synthesized, and their antifungal activity was tested. Some derivatives were equipotent or superior to amphotericin B in vitro but their relatively high toxicity in mice and their chemical instability discourage further evaluation.

4-Methylprimaquine (4-MPQ), an 8-aminoquinoline antimalarial drug, was subjected to microbial metabolism studies in an effort to isolate, identify, and predict the probable mammalian metabolite(s). Preliminary screening with a number of strains of Aspergillus indicated that several species were capable of metabolizing 4-MPQ to one major metabolite based on thin-layer chromatographic analysis. Preparative scale conversion of 4-MPQ using whole-cell suspensions of Aspergillus ochraceus afforded one major metabolite (4-MPQ-I). Based on spectroscopic and chemical evidence, the structure of the metabolite is proposed as 6-methoxy-8-(3-carboxyl-l-methylpropylamino)-lepidine.