Allergy-preventive flavonoids from Xanthorrhoea hastilis

Allergy-preventive activity was demonstrated for an extract of resins from Xanthorrhoea hastilis R. BR. in a search for allergy-preventive substances from natural sources. By bioassay-directed fractionation of this plant extract, a new flavanone, 3 ',5 '-dihydroxy-7,4 '-dimethoxyflavanone (1), and two new chalcones, 3,5,2 '-trihydroxy-4,4 '-dimethoxychalcone (2) and 5,2 '-dihydroxy-3,4,4 '-trimethoxychalcone (3), were isolated together with five known compounds, 5 '-hydroxy-7,3 ',4 '-trimethoxyflavanone (4), 3 '-hydroxy-7,4 '-dimethoxyflavanone (5), liquiritigenin 7-methyl ether (6), 4,2 '-dihydroxy-4 '-methoxychalcone (7) and sakuranetin (8). The structures of 1, 2 and 3 were elucidated by spectroscopic methods. All of these compounds showed allergy-preventive effects.