Hydroxysulochrin, a tea pollen growth inhibitor from the fungus Aureobasidium sp

A new plant growth regulator, hydroxysulochrin (1), together with sulochrin (2) was isolated from the culture filtrate of Aureobasidium sp. grown on a malt extract medium. The structures of 1 and 2 were established by spectroscopic methods. 1 and 2 inhibited tea pollen tube growth by 41% and 36% of the control value at a concentration of 100 mg/l, respectively. However, 1 and 2 showed no inhibitory effect on the growth of lettuce seedlings from 0.1 mg/l to 100 mg/l.