Background: The overproduction of nitric oxide (NO) is known to involve in various inflammatory processes. A methanol extract of the tubers of Ophiopogon japonicus was found to strongly inhibit NO production. The present paper deals with the isolation, structural identification and NO inhibitory effect of five compounds isolated from the MeOH extract of O. japonicus tubers.
Results: Three new compounds were elucidated to be (2R)-(4-methoxybenzyl)-5,7-dimethyl-6-hydroxyl-2,3-dihydrobenzofuran (1), 2-(2-hydroxyl-4-methoxy-benzyl)-5-methyl-6-methoxyl-2,3-dihydrobenzofuran (2), and 2-(4-hydroxy-benzyl)-5,6-dihydroxybenzofuran (3). In addition, two known compounds were isolated from a natural source for the first time including 2-(4-methoxy-benzyl)-6,7-dimethoxyl-2,3-dihydrobenzofuran (4), and 2-(4-methoxy-benzyl)-6,7-methylenedioxy-2,3-dihydrobenzofuran (5). The absolute configuration of compound 1 was determined by experimental and calculated circular dichroism spectra. The effects of the isolated compounds on LPS-induced NO production in RAW264.7 cells were evaluated. Compound 1 and 2 showed the inhibitory activity with IC50 values of 11.4 and 29.1 μM, respectively.
Conclusions: The class of 2-benzyl-2,3-dihydrobenzofuran is uncommon in nature. In this work, three such compounds were isolated from O. japonicus. Two of them showed promising anti-inflammatory activity by inhibition of NO production.
Keywords: 2-Benzyl-2,3-dihydroxybenzofuran; 2-Benzyl-benzofuran; Dihydrobenzofuran; Inhibition of NO production; Ophiopogon japonicas.