A new minor homoisoflavonoid from Caesalpinia sappan

Homoisoflavonoid is a special type of flavonoid with the perspectives of both chemical diversity and significant biological activities. During our ongoing studies on the discovery of novel homoisoflavonoids from traditional Chinese medicines, a new minor 3,4-di-O-substituted homoisoflavonoid, 3′,4-di-O-methylepisappanol (1), was isolated from Caesalpinia sappan, and its structure was determined to be (3R,4R)-3,7-dihydroxy-3-(3′-methoxy-4′-hydroxybenzyl)-4-methoxychroman by various spectroscopic analyses. Meanwhile, a known xanthone derivate, 2-methoxy-3-hydroxyxanthone (2) was also isolated, which is the first example from the genus Caesalpinia.