Abstract
Natural products remain a source of new drugs. Many plant-derived drugs have been introduced to the market and used as medicine in today’s society. However, only a small percentage of plants have been investigated for their chemical constituents and medicinal properties. This study aimed to determine the phytochemical constituents of species belonging to genera that have historical medicinal uses or known biological activities. Five species belonging to three families were investigated in this study: Croton dichogamus Pax (Euphorbiaceae family), Crinum sp. 6538, Crinum hardyi Lehmiller and of Crinum sp. 5629 (Amaryllidaceae family), and Toona sinensis M. Roem (Meliaceae family). The families and genera which were chosen for this study have been reported to possess various classes of compounds with different biological activities including anti-cancer activity. A total of thirty-three compounds were isolated in this study, of which five compounds were new and one was a new isomer. The roots of Croton dichogamus yielded fifteen compounds including four known sesquiterpenoids (CD.1-CD.4), one new enantiomer of a known sesquiterpenoid (CD.5), four known ent-clerodane diterpenoids (CD.6-CD.9), two new ent-halimane diterpenoids (CD.10-CD.11), one known crotofolane (CD.12), two new crotofolane diterpenoids (CD.13-CD.14) and one known triterpenoid (CD.15). The bulbs of Crinum sp. 6538, Crinum hardyi and of Crinum sp. 5629 gave nine compounds: one new alkaloid (CF.2), seven known alkaloids (CF.1, CF.3, CF.4, CF.5, CF.6, CH.1 and CS.3) along with an alkaloid salt (CF.7). The stem bark of Toona sinensis yielded nine compounds: five known triterpenoids (TS.1-TS.5), two known flavonoids (TS.6-TS.7) and two common phytosterols (TS.8-TS.9). The structures of these compounds were determined using nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry, electronic circular dichroism and optical rotation measurements. Some of the isolated compounds were screened in vitro for cell viability against Caco-2 (Human Colorectal Adenocarcinoma) cell lines by using the neutral red assay. CD.5 showed some activity with an IC50 of 24.1 µM. Selected compounds were submitted to the National Cancer Institute (NCI) in the USA for testing at one dose of 15 µg/ml NCI60 cell line panel. The mean values of growth inhibition of all compounds did not meet the criteria for further testing against the five-dose NCI60 cell line panel.