Japonicins A and B from the flowers of Inula japonica

Two new flavonols japonicins, A (1) and B (2), along with nine known flavonoids were isolated from an antidepressant fraction, which was separated from the 70% alcohol extract of the flowers of Inula japonica Thumb. The structures of compounds 1 and 2 were determined as 3,3',4',5,9,10-hexahydroxy-12-methylchroman[2,3-h]flavone and 8-(1-(3,4-dihydroxyphenyl)ethyl)-3,3',4',5,7-pentahydroxyflavone by the analyses of physical constants and spectral data. The special flavonoid structure having the substituent 1-phenylethyl at C-8 position was discovered for the first time.