Constituintes químicos e avaliação das atividades antioxidante, anticolinesterásica e antiinflamatória cutânea de Coutarea hexandra (Jacq.) k. Schum. (Rubiaceae)

Abstract

This work describes the isolation and structural elucidation of some chemical constituents as well as antioxidant, anticholinesterasic and skin anti-inflammatory activities of extracts and some of the isolated compounds from Coutarea hexandra (Jacq.) K. Schum. (Rubiaceae). In the antioxidant assays, extracts from roots and leaves, when compared to positive controls used, free scavenger radical and inhibited the formation of peroxide of the linoleic acid. In the anticholinesterase and anti-inflammatory assays, at 0.6 mg/ear, some extracts from roots were effective in inhibiting the effects of the anticholinesterase enzyme and the formation of ear edema. The phytochemical investigation of some active extracts from roots resulted in the isolation of three phytosteroids (sitosterol, stigmasterol and sitostenone), a diterpene (2β,3α-dihydroxy-11-oxo-ros-5-ene), two triterpenes (2β,3α-dihydroxy-11,16-dioxo- 5-ene-octanor-cucurbitacin and 23,24-diidrocucurbitacin F 25-acetate) and five 4-phenylcoumarin derivatives [5,7,8-trimethoxy-4-(3,4-dihydroxyphenyl)coumarin, 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl)-coumarin, 5,7,8-trimethoxy-4-(p-methoxyphenyl)coumarin, 5,7-dimethoxy-4-(3-hydroxy-4-methoxyphenyl)coumarin,and 5,7-dimethoxy-4-(p-methoxyphenyl) coumarin]. These compounds had their structures elucidated based on their NMR spectral data and by comparison with literature data. Among isolated compounds, 2β,3α-dihydroxy-11,16-dioxo-5-ene-octanorcucurbitacin and 2β,3α-dihydroxy-11-oxo-ros-5-ene are being reported for the first time; 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl)coumarin are being described for the first time as natural product and 5,7,8-trimethoxy-4-(3,4-dihydroxy-phenyl)coumarin occur for the first time in the Coutarea genus. In the anti-inflammatory assays, 5,7-dimethoxy-4-(pmethoxyphenyl) coumarin, 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl) coumarin, 5,7-dimethoxy-4-(3-hydroxy-4-methoxy-phenyl)coumarin and 23,24-dihydro-cucurbitacin F 25-acetate, at 0.6 mg/ear, inhibited the edema by 35, 67, 19 and 30%, respectively. In the DPPH assays, 5-hydroxy-7-methoxy-4-(p-hydroxyphenyl)coumarin (43.70 0.21 μg/mL) and 5,7,8-trimethoxy- 4-(3,4-dihydroxyphenyl)coumarin (20.85 0.53 μg/mL) free scavenger radical with IC50 values comparable to ascorbic acid and gallic acid, respectively. In the anticholinesterase assays, 2β,3α-dihydroxy-11-oxo-ros-5-ene showed inhibition of this enzyme.