Extractives from Guttiferae. Part XXII. The isolation and structure of four novel biflavanones from the heartwoods of Garcinia buchananii Baker and G. eugeniifolia Wall

Evidence is presented to show that the four biflavanones, GB-1, GB-1a, GB-2, and GB-2a, first isolated from the heartwoods of Garcinia buchananii Baker and G. eugeniifolia Wall, possess structures in which 4′,5,7-trihydroxyflavanone (naringenin) is linked at C-3 to the 8-(or 6-) position of the following flavanones: 3,4′,5,7-tetrahydroxyflavanone (aromadendrin), 4′,5,7-trihydroxyflavanone, 3,3′,5,7-pentahydroxyflavanone, (taxifolin), and 3′,4′,5,7-tetrahydroxyflavanone (eriodictyol). The biosynthesis of the GB biflavanones is discussed.