Terpenoids from Citrus unshiu Peels and Their Effects on NO Production

Two new compounds, 3-methyl-but-2-en-1-yl-1-O-β-xylopyranosyl-(1ʺ→2ʹ)-O-β-glucopyranoside (1) and 1-O-β-glucopyranosyl-6-hydroxy-2-methyl-hep-2-enoic acid (2), along with sixteen known terpenoids were isolated from the peels ofCitrus unshiu Markov. Their structures were elucidated based on extensive NMR analyses ( 1 H NMR, 13 C NMR, DEPT, COSY, HMQC, and HMBC) and high-resolution mass spectrometry. In addition, all isolates (1 - 18) were tested their effects on nitric oxide (NO) production in RAW264.7 cells. Limonin (15) showed to inhibit LPS-induced NO production in a concentration-dependent manner without cytotoxicity.