Phytochemical investigation of schizozygia coffaeoides baill. (apocyncaceae) for antimicrobial principles
The air dried and ground stem bark of Schizozygia coffaeoides was extracted with dichloromethane/methanol (1:1) by cold exhaustive percolation. This crude extract was subjected to different chromatographic techniques which led to the isolation M two steroids [stigmasterol (1) and ,B-sitosterol-3-0-glucoside (2)] and five alkaloids [schizozygine (3), 6,7-dehydro-19p-hydroxyschizozygine (4), schizogaline (5), isoschizogaline (6) and 3-oxo- 14a, 15a-epoxyschizozygine (7)]. Similarly the chromatographic separation of the root extract of Schizozygia coffaeoides led to the isolation of two steroids [1 and 2], five alkaloids [3,4, 6,7 and isoschizogamine (8)] and two anthraquinones [cassiamin A (9) and cassiamin B (10)]. The structure of these compounds were elucidated using spectroscopic methods including, IH and 13C NMR, COSY, NOESY, HMBC, HMQC and MS. Among the isolated compounds 7 is a new compound while 1 and 2 are isolated for the first time from the genus; while compounds 9 and 10 are reported for the first time from the family Apocynaceae. The crude extracts showed antimicrobial activity against Cryptococcus neoformans and Asperginus niger. Compound 4 showed antifungal activity against the fungi Cryptococcus neoformans, Candida albicans and Aspergillus niger at 1 mg/disc. Compound 5 and 8 showed antimicrobial activity against Staphylococcus aureus at 3 mg/disc. The antiplasmodial activities of the crude and two of the isolated compounds [3 and 5] were performed against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. The crude [IC5o = 11.19 ﾱ 1.56 ug/ml (W2), 8.35 ﾱ 1.52 ug/rnl (D6)], compound 3 [IC5o = 26.83 )lM (W2), 33.52 )lM (D6)] and compound 5 [IC5o = 13.06 )lM (W2), 23.24 )lM (D6)] showed good to moderate antiplasmodial activities. Hydrogenation of compound 3 was carried out to give dihydroschizozgine (11). The antimicrobial activity of this compound was also tested, but no significant activity was observed at 2.5 m /disc.
University of Nairobi, Kenya