Benzophenones and biflavonoids antioxidants from Rheedia edulis fruits (Clusiaceae)
As part of our ongoing studies of antioxidants from tropical edible fruits, we have studied Rheedia edulis Seem. Planch. & Triana [synonym: Garcinia intermedia (Pittier) Hammel]. Rheedia edulis is native to the Central American lowland tropical rain-forest, and it has sweet-tasting, yellow fruits that mature in late January to March. Guttiferone A, 8-desoxygartanin, podoscarpusflavone A, amentoflavone, and friedelin have previously been identified in the leaves of this species. The fruits were extracted in methanol and partitioned with chloroform, ethyl acetate, and n-butanol. The methanol extract displayed low antioxidant activity (IC50=118.1±0.94µg/ml) in the DPPH assay. The chloroform and ethyl acetate partition showed high activity, 23.4±1.28µg/ml and 41.4±3.66µg/ml respectively, while the n-butanol partition had moderate activity (68.0±1.41µg/ml). Guttiferone A, guttiferone E, isoxanthochymol, fukugetin, and volkensiflavone have been identified so far in the fruits of this species. Guttiferone A and isoxanthochymol were isolated and identified with 1D and 2D NMR experiments. Guttiferone E, isoxanthochymol, fukugetin and volkensiflavone were identified by HPLC and LC-MS using previously isolated standards. The antioxidant activity of these compounds has previously been reported, except for guttiferone A (IC50=46µM) which is comparable to gallic acid (IC50=35µM). A mixture of two benzophenones has been isolated as yellow oil and is currently under investigation.