Cyanidin and malvidin from Oryza sativa cv. Heugjinjubyeo mediate cytotoxicity against human monocytic leukemia cells by arrest of G2/M phase and induction of apoptosis

Oryza sativa cv. Heugjinjubyeo (Gramineae), anthocyanin-pigmented rice, having dark purple grains, is known broadly as enriched rice with an improved taste. Two bioactive compounds were isolated from the 0.5% HCl-ethyl alcohol soluble fraction of the aleurone layer of O. sativa cv. Heugjinjubyeo through an activity-monitored fractionation and isolation method. From spectral analysis, the cytotoxic components were the anthocyanidins cyanidin (1) and malvidin (2). The 50% growth inhibitory concentrations (IC50) of cyanidin and malvidin on U937, human monocytic leukemia cells, were 60 and 40 mug/mL, respectively. These compounds showed cytotoxicity through the arrest of the G(2)/M phase of cell cycle and induction of apoptosis.