Identification of phenolic compounds from a unique citrus species, finger lime (Citrus australasica) and their inhibition of LPS-induced NO-releasing in BV-2 cell line

Abstract

In this study, a unique citrus species (Citrus australasica) was selected, and its fruit characteristics, phenolic compounds and ability to inhibit inflammation were preliminarily studied. Finger lime fruits showed distinctive features in shape, size, weight, colour, total soluble solids, water-soluble pectin, sugar and acids contents. Combining UPLC-HRMS and UPLC-DAD analysis, 31 phenolics, 1 secoiridoid derivative and 1 neolignan glycoside were preliminarily identified and quantified. The phenolics composition of finger limes showed cultivar and tissue specificity. Antioxidant evaluation showed that extracts from finger lime cultivar of ‘XiangBin’ exhibited better antioxidant capacities than cultivar of ‘LiSiKe’, especially in peel. LPS-induced NO-releasing model was performed in the mouse microglia BV-2 cell line. Results illustrated that finger limes inhibited the NO-releasing and the inflammation-related cytokines including IL-1β, IL-6 and TNFα elevation. QRT-PCR revealed that finger lime extracts alleviated LPS-induced upregulation of iNOS, IL-6, JAK2, TNFα, TLR2, TLR4, IL-1β, NF-κB and LPS-induced downregulation of IκBα. This study may expand our knowledge on the physiochemical characteristics and bioactive properties of citrus fruits.