Two spiroketal derivatives with an unprecedented amino group and their cytotoxicity evaluation from the endophytic fungus Pestalotiopsis flavidula

Abstract Two new spiroketal derivatives with an unprecedented amino group, 2′-aminodechloromaldoxin ( 1 ) and 2′-aminodechlorogeodoxin ( 2 ), along with one known analogue dechloromaldoxin ( 3 ), were isolated from the plant endophytic fungus Pestalotiopsis flavidula. Their structures were elucidated on the basis of extensive spectroscopic analysis. The purification was cytotoxicity-guided which indicated the extract, fractions and compounds were evaluated in vitro for anti-proliferative activity against a panel of human cancer cell lines. The results showed compounds 1 and 2 with moderate cytotoxicity while 3 was inactive, which suggested -NH 2 group might play a very important role for their cytotoxicity. This is the first study for P. flavidula and the first time to report the spiroketal derivatives as alkaloids from the Pestalotiopsis genus.