Mechanism of growth inhibitory effect of cape aloe extract in ehrlich ascites tumor cells.

Cape aloe (Aloe ferox Miller) has been a herb well known for its cathartic properties and has also been used popularly as a health drink (juice, tea and tonic) in the United States and in Europe. Cape aloe extract also has been reported to possess several pharmacological effects, such as anti-inflammatory, anti-bacterial, anti-fungal and protective effect against liver injury. However, the investigations on an anti-tumor activity in cape aloe extract are very few and subsequent mechanisms have not been well elucidated. In this study, we examined the effect of the selective growth inhibitory activity of cape aloe extract and found that the cape aloe extract, especially the dichloromethane (CH(2)Cl(2)) extract, caused a dose-dependent growth inhibitory effect in Ehrlich ascites tumor cells (EATC), but not in mouse embryo fibroblast (NIH3T3) cells, which was used as a normal cell model. Furthermore, the CH(2)Cl(2) extract caused an accumulation of cells in the G1 phase and a decrease of cells in the S and G2/M phase of the cell cycle and inhibited DNA synthesis in a dose-dependent manner. In addition, other results suggest that cell cycle arrest and inhibition of proliferation in EATC by the CH(2)Cl(2 )extract are associated with decreased retinoblastoma protein (Rb) phosphorylation.

Chemical constituents of cape aloe and their synergistic growth-inhibiting effect on Ehrlich ascites tumor cells.

The constituents of cape aloe were investigated after a preliminary screening of the growth-inhibiting effect on Ehrlich ascites tumor cells (EATC) of several extracts of this plant. Ten compounds were isolated from the dichloromethane (CH(2)Cl(2)) extract that showed the strongest activity, and their structures were elucidated as aloe-emodin (1), p-hydroxybenzaldehyde (2), p-hydroxyacetophenone (3), pyrocatechol (4), 10-oxooctadecanoic acid (5), 10-hydroxyoctadecanoic acid (6), methyl 10-hydroxyoctadecanoate (7), 7-hydroxy-2,5-dimethylchromone (8), furoaloesone (9), and 2-acetonyl-8-(2-furoylmethyl)-7-hydroxy-5-methylchromone (10) based on MS and various NMR spectroscopic techniques. Compounds 2-7 were isolated for the first time from cape aloe. Compounds 4-7 and 10 showed a significant growth-inhibiting effect, and compound 1 exhibited a remarkable synergistic effect on compounds 8-10, which was not observed with the treatment by each compound alone on EATC. These results suggest that the strong growth-inhibiting effect of the CH(2)Cl(2) extract was dependent not on one compound alone, but on the synergistic effect from the combination of compound 1 and the other compounds.