Daylilies (Hemerocallis) are used medicinally in eastern Asia and extracts of the plant had been shown to inhibit cell proliferation and induce
cancer cells to undergo differentiation. In our studies of the constituents of Hemerocallis fulva var. 'Kwanzo' roots, we isolated a series of new [kwanzoquinones A (1),
B (2), C (4), D (5), E (6), F (7), G (9)] and known [2-hydroxychrysophanol (3) and
rhein (8)]
anthraquinones. These compounds were tested in order to determine their potential roles as
cancer cell growth inhibitors. Kwanzoquinones A-C and E,
kwanzoquinone A and B monoacetates (1a and 2a),
2-hydroxychrysophanol, and
rhein inhibited the proliferation of human breast, CNS, colon, and
lung cancer cells with GI50 values between 1.8 to 21.1 microg/mL. However, upon exposure of the
cancer cells to the GI50 concentrations of the bioactive
anthraquinones, most of the
cancer cell lines exhibited higher than anticipated levels of cell viability. Co-incubation of the
anthraquinones with
vitamins C and E increased the viability of
breast cancer cells. In contrast,
vitamins C and E potentiated the cytotoxic effects of the
anthraquinones against the
colon cancer cells. None of the
anthraquinones inhibited the activity of topoisomerase.