Five eudesmane-type sesquiterpene glycosides, named sonneratiosides A-E (1-5), were isolated from the leaves of Sonneratia alba (Lythraceae). The aglycone of sonneratioside A was identified as cryptomeridiol also known as proximadiol. X-ray crystallographic analysis of sonneratioside A confirmed its structure and its absolute stereochemistry. Eudesmol β-D-glucopyranoside (6) was also isolated from nature for the first time. The tyrosinase inhibitory activity was assayed for the new compounds together with seven known compounds. Among them, arbutin (12) showed the expected activity and luteolin 7-O-rutinoside (10) showed comparable activity to arbutin.
Keywords: Eudesmane; Lythraceae; Sesquiterpene; Sonneratia alba; Sonneratioside; Tyrosinase inhibitory activity.