Compounds isolation and biological activities of Piptadeniastrum africanum (hook.f.) Brennan (Fabaceae) roots

Abstract Ethnopharmacological relevance The dicotyledonous plant Piptadeniastrum africanum (hook.f.) Brennan (Fabaceae) is used in traditional medicine to treat various human complaints including bronchitis, cough, various urino-genital, meningitis, abdominal pain, wound treatment malaria and gastrointestinal ailments and as a purgative and worm expeller. Aim of the study: The present study describes the phytochemical investigation and the determination of the antimicrobial, antiplasmodial and antitrypanosomal activities of fractions and compounds extracted from Piptadeniastrum africanum roots. Materials and methods Isolated compounds were obtained after several chromatographic techniques. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR) and by comparing their NMR data with those found in literature. In vitro antimicrobial activity of samples was evaluated using the microdilution method on bacteria (Escherichia coli, Proteus mirabilis, Staphylococcus aureus) and fungi (Candida krusei) strains while in vitro cell-growth inhibition activities were assessed against two parasites including Trypanosoma brucei brucei and Plasmodium falciparum strain 3D7. The cytotoxicity properties of samples were assayed against HeLa human cervical carcinoma. Results Five compounds were isolated and identified as: tricosanol 1, 5α-stigmasta-7,22-dien-3-β-ol 2, betulinic acid 3, oleanolic acid 4 and piptadenamide 5. All the five compounds are reported here for the first time from the roots of P. africanum. The hexane-ethyl acetate (EtOAc) 50% fraction exhibited moderate antibacterial activity against P. mirabilis (MIC 250 μg/mL) while the other fractions and the isolated compounds showed a weak antimicrobial activity. Only the EtOAc fraction presented a moderate antimalarial activity with an IC50 of 16.5 μg/mL. The MeOH crude extract and three fractions (Hexane, Hexane-EtOAc 25% and EtOAc-MeOH 25%) exhibited significant trypanocidal activity with IC50 values of 3.0, 37.5, 3.8 and 9.5 μg/mL, respectively. Conclusion These results demonstrated a scientific rational of the traditional uses of P. africanum and indicate that this plant should be further investigated to identify some of the chemical components that exhibited the activities reported from this study and therefore may constitute new lead candidates in parasiticidal drug discovery.