Chemical Constituents from Citrus changshan‐huyou and Their Anti‐Inflammatory Activities

A systematically chemical investigation of Citrus changshan-huyou Y.B.Chang resulted in the isolation and structure determination of twelve known natural products, including limonoid, nootkatone, scoparone, β-sitosterol, 3,3',4',5,6,7,8,-heptamethoxyflavone, nobiletin, tangeretin, naringin, hesperidin, neohesperidin, 3,5-dihydroxyphenyl β-D-glucoside, β-sitosterol-D-glucoside. The structure modification of the most abundant compound limonin further led to eight limonoid derivatives, including epi-limonol, epi-limonyl acetate, and six new compounds epi-limonol A, limonol A, limonol B, epi-limonol B, epi-limonol C, epi-limonol D, which enlarged the chemical diversity of limonin related limonoids. The structures of the new limonoid derivatives were identified by extensive spectroscopic analysis. In bioassay, all the isolates, the semi-synthetic derivatives and the previously isolated limonoids in our natural product library were subjected for anti-inflammatory activities evaluation, and several limonoids exhibited the inhibition of TNF-α release.