Effect of Rheedia longifolia leaf extract and fractions on the [P2X.sub.7] receptor in vitro: novel antagonists?

Recently, the [P2X.sub.7] receptor has been reported to be associated with chronic inflammatory and neuropathic pain. Because Rheedia longifolia extract has analgesic and anti-inflammatory activity, we evaluated the in vitro inhibitory potential of methanol extract and fractions from its leaves on the [P2X.sub.7] purinergic receptor. The activity of [P2X.sub.7] was studied with a dye uptake assay and with the whole-cell patch clamp technique in mouse peritoneal macrophages treated with methanol extract of R. longifolia leaves and fractions. The dye uptake was evaluated by flow cytometry and fluorescence microscopy. The R. longifolia extract and some fractions showed an inhibitory effect on the [P2X.sub.7] purinergic receptor in a dose-dependent manner. The ethyl acetate fraction exhibited the most potent inhibitory effects. The methanol extract and the butanol fraction showed the same inhibitory effects, despite their lower potency compared with the other fractions. The R. longifolia extract and some of its fractions may be anti-inflammatory because of their inhibitory effect on the [P2X.sub.7] receptor. Further investigation is needed to determine the pattern of inhibition and selectivity. Chromatographic analysis indicated the presence of bisflavonoids in the methanol extract fractions. A member of this chemical family is the most probable active compound responsible for the [P2X.sub.7] inhibitory effects present in the R. Longifolia extract and fractions. KEY WORDS: * anti-inflammatory and analgesic effect * inflammation * [P2X.sub.7] antagonist * Rheedia longifolia