Xanthones from heartwood

New oxygenated xanthones were characterized from heartwood, root and leaf extracts of H. geminiflorum [74,75], namely a) 2, 3-dihydroxy-... 

Bhanu S, Scheinmann F, Jefferson A 1975 Xanthones from the heartwood of Calophyllum ramiflorum. Phytochemistry 14 298-299... 

Rama Rao, A.V., Sarma, M.R., Venkataraman, K. and Yemul, S.S. (1974) A benzophenone and xanthone with unusual hydroxylation patterns from the heartwood of Carcinia pedunculata. Phytochemistry 13(7), 1241-1244. 

Benzophenones are derived from several pathways. In higher plants, most benzophenones arise by cyclization of a polyke-tide chain of three malonates added to a hydroxybenzoic acid precursor (Manitto, 1981). Cyclization occurs via a Claisen condensation mechanism (Fig. 10.14). These compounds serve as precursors for xanthones in many plants. In some instances [e.g., in the heartwood of Symphonia globulifera (Clusiaceae)], the benzophenone and the corresponding xan-thone co-occur [in this case maclurin (33) and 1,3,5,6-tetra-hydroxyxanthone (34)] (Weiss and Edwards, 1980). 

Owen P J, Scheinmann F 1974 Extractives from Guttiferae. Part XXVI. Isolation and structure of six xanthones, a biflavanoid, and triterpenes from the heartwood of Pentaphalangium solomonse Warb. J Chem Soc Perkin Trans I 1018-1021... 

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