Chemical and Toxicological Studies of the Phytotoxin, 6α,7β,9α-Trihydroxy-8(14), 15-isopimaradiene-20,6-γ-lactone, Produced by a Parasitic Fungus, Phomopsis sp., in Wilting Pine Trees

A phytotoxin, isopimarane diterpene γ-lactol, 6α,7β,9α-trihydroxy-8 (14),15-isopimaradiene- 20,6-γ-lactone, was isolated from the culture filtrate of the fungus Phomopsis sp., which was obtained from the interior part of the trunk of most wilting Japanese red pines, Pinus densiflora I Sieb, et Zucc. The stereostructure was established by X-ray crystal analysis and spectroanalysis. This γ-lactol was identical with LL-S491, a fermentation product of the fungus Aspergillus chevalieri. The cytotoxic activity of the γ-lactol isopimarane was the same as pentachlorophenol at 150 ppm on cell cultures from Japanese red pine buds.