Pestacin:: a 1,3-dihydro isobenzofuran from Pestalotiopsis microspora possessing antioxidant and antimycotic activities

Pestalotiopsis microspora, an endophytic fungus native to the rainforest of Papua New Guinea, produces a 1,3-dihydro isobenzofuran. This product, pestacin, is 1,5,7-trisubstituted and exhibits moderate antifungal properties and antioxidant activity 11 times greater than the vitamin E derivative trolox. Antioxidant activity is proposed to arise primarily via cleavage of an unusually reactive C-H bond and, to a lesser extent, through O-H abstraction. Isolation of pestacin was achieved by extraction of culture fluid with methylene chloride followed by silica gel chromatography. Structure was established by X-ray diffraction and C-13 and H-1 NMR. The X-ray data demonstrate that pestacin occurs naturally as a racemic mixture. A mechanism for post-biosynthetic racemization is proposed. (C) 2003 Elsevier Science Ltd. All rights reserved.