Exploring the unique antioxidative and anti-inflammatory properties of aging black lemon (Citrus limon L. Brum. F.)

The aging black lemon is a dried citrus fruit, generally made from lemon, which is lightly thermal processed until it takes on the appearance of blackish-brown leather. This study aimed to determine the phenolic and flavonoid components in aqueous black lemon extract (ABLE). FRAP was used to determine the antioxidant capacity of ABLE. The effects of ABLE on LPS-induced NO production in macrophages (RAW264.7) were investigated by measuring the amount of nitrite released into the culture medium using the Griess reaction. For the anti-inflammatory effects, pro-inflammatory mediators, including iNOS, TNF-α, and NF-κB, were examined by Western blotting. In addition, UPLC/MS/MS data of ABLE presented higher concentrations of gallic acid, protocatechuic acid, vanillic acid, p -coumaric acid, ferulic acid, luteolin, naringenin, hesperetin, and diosmetin than fresh lemon. Based on the results, we consider ABLE to have outstanding anti-inflammation properties by polyphenols and flavonoids and is a great functional food for inflammation-related diseases. • The best aging conditions of black lemons have been clarified. • Aging black lemon has good potential for anti-oxidation and anti-inflammation. • The possible active components of anti-oxidation and anti-inflammation were discussed in aging black lemons. • A possible mechanism for the anti-inflammation of aging black lemons is proposed.