Chemical Constituents of the Flowers of Pueraria lobata and Their Cytotoxic Properties.

The flower of Pueraria lobata (Puerariae Flos) is a reddish-purple to violet-purple flower that blooms between July and September. In our preliminary study, Puerariae Flos extract exhibited significant activity against a human ovarian cancer cell line. This research aims to identify the active compounds in Pueraria Flos. By repeated chromatography, one new tryptophan derivative ( 1 ), two new flavanones ( 4 and 5 ), and 19 known compounds, including tryptophan derivatives ( 2 and 3 ), flavonoids ( 6 - 9 ), isoflavonoids ( 10 - 20 ), a flavonolignan ( 21 ), and a phenolic compound ( 22 ), were isolated from a methanol extract of Puerariae Flos. The structures of new compounds were elucidated as 13- N -benzoyl-l-tryptophan-1- N-β -d-glucopyranoside ( 1 ), 2-hydroxy-5-methoxy-naringenin ( 4 ), and 2-hydroxy-5-methoxy-naringenin 7- O - β -d-glucopyranoside ( 5 ). Among the isolates, afromosin ( 17 ), tectorigenin ( 11 ), apigenin ( 8 ), glycitein ( 16 ), (-)-hydnocarpin ( 21 ), irilin D ( 12 ), irisolidone 7- O -glucoside ( 14 ), and genistein ( 10 ) showed cytotoxicity against human ovarian cancer cell line A2780. Apigenin ( 8 ) and (-)-hydnocarpin ( 21 ) were the most active (IC 50 values of 9.99 and 7.36 μM, respectively).