Prenylated benzenepropanoic acid analogues from the Citrus grandis (L.) Osbeck and their anti-neuroinflammatory activity

Phytochemical studies of the air-dried pericarp of Citrus grandis led to the isolation of four new compounds including three prenylated benzenepropanoic acids (2, 3 and 5) and one alkamidic glycoside (6), together with ten known compounds (1, 4 and 7-14). The structures of these compounds were determined by the NMR spectroscopy, optical rotation data and modified Mosher's method. Meanwhile, the anti-neuroinflammatory activities of all isolated compounds were evaluated by detecting the production of nitric oxide (NO) in LPS-stimulated BV2 cells. The results showed that compounds 1, 2, 5 and 13 exhibited strong inhibition effects on NO production in LPS-stimulated BV2 cells. Mechanistically, compounds 1, 2 and 5 could suppress the expressions of iNOS. In addition, compounds 1, 2 and 5 also showed obvious inhibition effects on COX-2 expression, another vital enzyme in the inflammation process, in LPS-treated BV2 cells. These findings shed light on the potent anti-neuroinflammatory effects of Citrus grandis.