JUP and leukemia: flavonoid-rich fractions from fermented Pg juice and aqueous extraction of Pg pericarps are strong promoters of differentiation in human HL-60 promyelocytic leukemia cells, which are detected by nitro blue tetrazolium reducing activity, non specific esterase activity, specific esterase activity, and phagocytic activity, whereas flavonoid-rich fractions from fresh Pg juice only show a relatively mild differentiation-promoting effect.