Abstract:
The chemistry of natural products is very important since it has been used in the search for bioactive compounds for management of various human diseases including cancer. The increase in the incidence of cancer coupled with the undesirable side effects observed with chemotherapic agents urges the discovery of new agents from natural sources. In this study the four ethnomedicinal plants; Dovyalis abyssinica (Salicaceae), Solanum mauense (Solanaceae), Syzigium guinense (Myrtaceae) and Croton dichogamous (Euphorbiaceae) were investigated for their unvalidated anticancer activities. Crude extracts for stem bark of S. guinense, fruits of S. mauense, and roots of both D. abbysinica and roots of C. dichogamous were prepared via cold extraction method. The crude extracts were purified by repeated column chromatography and Thin Layer Chromatography. This resulted in various pure compounds which were analysed by use of 1D NMR, 2D NMR spectroscopic techniques and MS spectrometry. The NMR spectral data obtained together with MS data were interpreted, the structures of the compounds elucidated and their chemical structures proposed. A total of twelve compounds were isolated, purified, their chemical structures proposed and four of these compounds were evaluated for their anticancer activity. Two previously reported compounds; β-sitosterol (47) and betulinic acid (21), were obtained from stem bark extracts of S. guinense as well as from the fruits extracts of S. mauense. Two previously reported compounds; Tremulacin (29) and Benzoic acid (48) were isolated from the roots extract of D. abyssinica. Eight compounds were isolated from roots extract of C. dichogamous; Acetyl aleuritolic acid (49), 3β,4β:15,16-diepoxy-13(16),14-ent-clerodadiene (50), 3β, 4β:15, 16-diepoxy-13(16), 14-ent-clerodadien-17,12S-olide (51), 15,16-epoxy-5, 13(16), 14-ent-halimatriene-3-ol (52), crotodichogamoin A (53), crotohaumanoxide (54), crotodichogamoin B (55) and Cadin-1(6),2,4,7,9-penta-ene (56). Selected compounds were evaluated for their anticancer activity by use of cancer cell lines. Betulinic acid (21) was screened against 57 cell lines and only 25 gave positive results. Acetyl aleuritolic acid (49), 15,16-epoxy-5,13(16),14-ent-halimatriene- 3-ol (52) and crotodichogamoin A (53) were also evaluated for their anticancer activity and and their one dose mean value percentage growth at 15 μg/ml were 97.86, 99.39 and 100.6, respectively. The mean values of growth inhibition of the three compounds tested against one dose NCI cell line panel did not meet the standards for further testing against the five-dose NCI cell line panel. The study recommends toxicological studies be done on the medicinal plants extracts to enhance their full exploitation.
