Antioxidants from Uvaria rufa Blume roots

Abstract

In the research for antioxidant from medicinal herbs, the 40 Thai medicinal plants were preliminary evaluated using TLC autographic assay with 2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) as a stable radical. The CH[subscript 2]CI[subscript 2] and butanolic extracts of Uvaria rufa roots (Pee-Puan-Noi) were found to have a promising activity. Therefore, this plant was selected for futher investigation. Chromatographic separation of these two extracts led to the isolation of fifteen known compounds. Six flavonoids, 2,5-dihydroxy-7-methoxy flavanone (1), tectochrysin (2), 5-hydroxy-7-methoxy flavanone (3), 6,7-O,O-dimethylbaicalein (6), 7-O-methylwogonine (7) and 2,5-dihydroxy-6,7-dimethoxy flavanone (8), together with two aromatic compounds, benzyl benzoate (4) and 2-methoxybenzyl benzoate (5), were isolated from the CH[subscript 2]CI[subscript 2] crude extract. While seven alkaloids, liriodenine (9), lanuginosine (10), oxoanolobine (11), roemerine (12), anonaine (13), xylopine (14) and roemeroline (15) were isolated from butanolic crude extract. All the compounds, except for 1, 2, 6 and 7, were isolated from this plant for the first time. The structures of all isolated compounds were elucidated on the basis of spectroscopic methods, as well as comparison with previously reported. The antioxidant capability was determined using three complementary in vitro assays, the DPPH radicals scavenging activity, the superoxide radicals scavenging activity and the inhibition of xanthine oxidase activity. Compound 8 showed the highest scavenging activity on DPPH and superoxide radicals with IC[subscript 50] value 0.16 and 1.03 mg/mL, respectively. In addition, the inhibitory activity against xanthine oxidase, no compounds displayed good activity as a xanthine oxidase inhibitor.