A comprehensive study of defatted Idesia polycarpa fruit: Phenolic profile and its relation with anti-inflammatory activity in seed, pulp, and whole fruit

Defatted seed, pulp and whole fruit of Idesia Polycarpa Maxin. (I. Polycarpa) are the by-products of the oil extraction process, but have attracted little attention as natural sources of bioactive phenolics. This study aimed to clarify the profiles of phenolic compounds in the extracts from these by-products and their contribution to the anti-inflammatory activity. Twenty-one phenolic compounds were identified, belonging mainly to salicinoid analogues and p-coumaroyl derivatives. Idescarpin was the predominant phenolics in all extracts, especially in seed extract. Nearly half the p-coumaroyl derivatives presented relatively high content in the extracts of pulp and whole fruit. All extracts inhibited the production of nitric oxide (NO) and the mRNA expressions of inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF-α), and interleukin (IL)-6; and suppressed the accumulation of reactive oxygen species (ROS) along with the restoration of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities. Seed extract exerted better potential than the pulp and whole fruit extracts. Furthermore, correlation analysis demonstrated that idescarpin and idesin were the crucial phenolics against inflammation, whereas some p-coumaroyl derivatives contributed to regulating oxidative stress. These findings suggested that phenolic extracts from defatted I. Polycarpa fruit and its parts, especially seed, could be utilized as inflammation inhibitors in the functional food and cosmetics industries.