Faculty: Pharmaceutical Sciences
Department: Pharmaceutical And Medicinal Chemistry
Ajaegbu E. Eze
Okoye F. B. C
Eboka C. J
Medicinal plants are potential sources of bioactive compounds. Millettia aboensis being common in Nigeria has recently generated significant interest in drug discovery scheme due to its immense potential to contribute to the discovery of new bioactive compounds. This study was aimed at the isolation and structural elucidation of bioactive compounds from M. aboensis. Specific objectives include: extraction and fractionation of the crude extract from the plant parts of the M. aboensis; isolation and structural elucidation of the bioactive secondary metabolites from M. aboensis; bioassay of the bioactive secondary metabolites. The root, leaf, stem and pod of M. aboensis were extracted in methanol using cold maceration. The crude extracts of the various plant parts were fractionated using liquid-liquid method, and the fractions subjected to several chromatographic separation methods: vacuum liquid chromatography, Sephadex LH-20, and semi-preparative HPLC to obtain pure compounds. The resulting fractions and isolated compounds were subjected further to HPLC-DAD analysis. The structures of the isolated compound were elucidated using Mass Spectroscopy, 1D and 2D Nuclear Magnetic Resonance spectroscopy. The crude extracts were screened for cytotoxicity test using mouse lymphoma cell line (L5178Y). The isolated compounds were screened for antioxidant assay using 1,1-diphenyl-2-picrylhydrazyl scavenging method. The root, leaf, stem and pod crude extracts of M. aboensis at 10 µg/ml showed cytotoxic activity against mouse lymphoma cell line (L5178Y) with growth inhibitions of 87.5%, 31.4%, 68.5%, and 36.7%, respectively. Spectral analysis of the compounds showed one new compound genistein-4’-O-arabinofuranoside and four known compounds - decyl pent-2-enedioic acid, epicatechin-3-O-(4-methyl gallate), protocatechuic acid, and gallic acid isolated from the leaf. Seven new compounds - 3,8-dimethoxy pterocarpan, derrisisoflavone M, 4’-methoxy orobol , 3’, 4’-methylenedioxy pterocarpan, 2’,3’-diethyl kaempferol, 3’-methoxy daidzein, derrisisoflavone O and two known compounds - derrisisoflavone G and orobol were isolated from the root. One known compound – luteolin was isolated from pod, while two new compounds - derrisisoflavone L and derrisisoflavone N were isolated from the stem. Of all the compounds screened for antioxidant activity, compounds 3’, 4’-methylenedioxy pterocarpan and luteolin showed good antioxidant activity with IC50 at 83 µg/ml. A total of seventeen bioactive compounds were isolated from the various plant parts of M. aboensis. The high cytotoxicity activity recorded by the root crude extract may be attributed to the derrisisoflavones and pterocarpans present in the root, which have been reported to have cytotoxicity activity. These secondary metabolites isolated from M. aboensis could serve as novel therapeutic compounds.