Flavonoid composition of orange peel and its association with antioxidant and anti-inflammatory activities

Dried citrus peel derived from Citrus reticulate!, also called chenpi, possesses a complex mixture of flavonoids and has a history of traditional use to treat a variety of digestive disorders. We compared three sources of conventional chenpi from California (USA), Guangxi, Zhejiang, and two sources of nchenpi, which contain greater nobiletin content, from Sichuan and Xinhui (China). Xinhui orange peel extract (OPE) had highest content of polymethoxylated flavones, along with greatest capacity to scavenge 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-l-perylhydrazyl (DPPH), and 2,2'-azobis-2-methyl-propanimidamide, dihydrochloride (AAPH) radicals and nitric oxide (NO). OPE also had higher NO, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) inhibitory activity than an equivalent mixture of flavonoids (P < 0.05). In conclusion, nobiletin is a good chemical marker for assessing the anti-inflammatory potential of OPE from different sources. Obtaining nchenpi from either Sichuan or Xinhui provided potentially superior health benefits compared to conventional chenpi sources. (C) 2016 Elsevier Ltd. All rights reserved.