Cytotoxic and antimicrobial activities of substituted phenanthrenes from the roots of Combretum adenogonium Steud Ex A. Rich (Combretaceae)

AIM The aim of this study was to isolate the bioactive compounds from the roots of Combretum adenogonium and assess for its antibacterial and cytotoxic properties. MATERIALS AND METHODS The extract was obtained using 20% aqueous ethanol and further subjected to fractionation with 1:1 n-butanol/water. Chromatographic analyses of the n-butanol fraction led to the isolation of compounds (1-3). The compounds (1-3) were assayed for antibacterial activities using two-fold microdilution methods and cytotoxicity using brine shrimps lethality assay. RESULTS Following spectroscopic analyses the compounds were established as 2,3,8-trihydroxy-4,6-dimethoxyphenanthrene (1a) and 2,3,8-trihydroxy-4,6-dimethoxy-9,10-dihydrophenanthrene (1β). Compound 2 was derived from 2,3,8-trihydroxy-4,6-dimethoxyphenanthrene condensation with methyl acetate while Compound 3 was derived from 2,3,8-trihydroxy-4,6-dimethoxy-9,10-dihydrophenanthrene condensation with methyl propionate. These compounds (1-3) were active against Pseudomonas aeruginosa with minimal inhibitory concentration-value of 0.16 mg/ml. The compounds (1-3) also exhibited significant toxicity with LC50 (95% confidence interval [CI]) of 12.11 (7.32-20.05) µg/ml compared to standard anticancer drug, cyclophosphamide which had LC50 (95% CI) value of 16.37 (12.01-22.31) µg/ml. CONCLUSION These compounds add for a novel structure that can be synthesized, further screened for in vitro and in vivo models and clinical trials in order to evaluate its potential for further development as new anticancer agent.