Secondary metabolites from newtonia paucijuga and erythrina sacleuxii and bioactivities of their extracts.

The phytochemical investigations reported in this dissertation aimed at establishing the chemical constituents, antiplasmodial and antimicrobial activities of the two plants from the family Fabaceae, viz. Newtonia paucijuga and Erythrina sacleuxii. The crude extracts were subjected to chromatographic separation to afford the pure compounds. The antiplasmodial activities were evaluated using malaria imaging assay method, while the antimicrobial activities were carried out by disc diffusion and broth microdilution methods. Mearnsetin-3-O-α-L-rhamnopyranoside (2.26), benzyl-3,4,5-trihydroxylbenzoate (2.28) and, the mixture of stigmasterol (2.37a) and β-sitosterol (2.37b) were isolated from the ethanolic extracts of leaves, root and stem barks of N. paucijuga, respectively. Chromatographic isolation of ethanolic extracts of the E. sacleuxii leaves yielded a new nor-sesquiterpenoid namely, sacleuxenone (2.38). The structure elucidation of the compounds was based on the 1D and 2D NMR, IR and Mass spectral data. The extracts from the leaves, stem and root barks of N. paucijuga and leaves of E. sacleuxii exhibited moderate antibacterial activities with activity index value ranging from 0.3 - 0.5 against Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonia. The most potent were the leaves and stem bark extracts of N. paucijuga (AI = 0.5). The minimum inhibitory concentrations (MIC) for the active extracts ranged from 0.3 - 5.0 mg/mL against S. aureus, P. aeruginosa, K. pneumonia and B. subtilis. All the extracts were active against B. subtilis with MIC value of 0.3 mg/mL. No any activities were observed against all the fungal species tested. On the other hand, all extracts exhibited antiplasmodial activity against Plasmodium falciparum (3D7 strain) with an IC50 value ranging from 2.6 – 24.6 μg/mL with selectivity index (SI) against human embryonic kidney 293 cell lines ranging from 6.5 – 21.0. The most potent antiplasmodial was Newtonia paucijuga root barks extract (NPRE) (IC50 = 2.6; SI = 6.5). Most extracts were safe against HEK 293 cell lines at the concentration of 40 μg/mL. Pure compound were not assayed for their antiplasmodial and antimicrobial activities due to insufficient amount. The study indicated that ethanolic crude extracts from N. paucijuga and E. sacleuxii have antibacterial and antiplasmodial activities and are recommended for further investigations.