Cytotoxic effects of new bioactive compounds isolated from a Nigerian anticancer plant Melastomastrum capitatum Fern. leaf extract

Abstract

The use of medicinal plants in human's health care delivery system in Nigeria exist for decades. Medicinal plants have been used to treat diseases such as malaria fever, cancers, hypertension, microbial infections, among others in Africa of which Melastomastrum capitatum is one of such plant. The plant has been used to cure many diseases notably cancer of the ovary in women by Fulani herdsmen. Hence, this study was carried out in order to isolate major bioactive compounds from the leaf of M. capitatum, and evaluate their cytotoxic effects on cancer cell lines. Methanol extracted was partitioned successively with solvents of varying polarities in ascending order, bio-monitored by anticancer activities. Fractions with the most anticancer activity after 24 hours’ incubation were purified in a silica gel column chromatography. Isolated bioactive compounds from ethyl acetate leaf extract of M. capitatum were then characterized using GC–MS, while in vitro anticancer activity was determined by MTT bio-assay on MCF-7, HMVII and OV-7 cell lines. Five compounds which are mainly saturated fatty acid esters and phthalate acid derivatives were isolated. They include di-benzofuran, 3-nitro (Z, 211.0; RT, 14.08 min), di‑butyl phthalate (Z, 278; RT,14.09 min), 2,4,7-trioxabicydo (4.4.0)9-decene, 8(4-(4-pentylcyclohexyl) cyclohexyloxy)-3-phenyl (Z, 467; RT, 14.31 min), 9- octadecenoic acid E, oleic acid (Z, 294.45; RT, 15.94 min) and phthalic acid-di(2-propylpentyl) ester (Z, 390.56; RT, 19.44 min). The compounds were cytotoxic against breast cancer cell line MCF-7, woman vagina melanoma cell line HMVII and ovarian cancer cell line OV-7. Two of the compounds showed high selective indices on breast and ovarian cancer cell lines. Oleic acid, Di-benzofuran-3-nitro, 2,4,7-Trio-B (4.4.0)-9D..... and DiBP ester showed IC50 values of 2.12 ± 0.01 μg/mL, 24.13 ± 6.12 μg/mL, 6.03 ± 0.21 μg/mL and 31.01 ± 5.04 μg/mL respectively on OV-7 cell line which were better than the values shown on MCF-7 and HMVII cell lines in vitro. The results showed that M. capitatum leaf extract possessed compounds which are cytotoxic on cancer cells. The plant's leaf might be a source for the discovery of new anticancer drug.