Isoquercitrin isolated from newly bred Green ball apple peel in lipopolysaccharide-stimulated macrophage regulates NF-κB inflammatory pathways and cytokines.

Apple peel has several bioactive properties. The fruit is grown worldwide, and its ingredients are used medicinally. However, its anti-inflammatory activities are poorly characterized. In this study, isoquercitrin isolated from newly bred Green ball apple peel from Korea showed anti-inflammatory effects. To confirm its anti-inflammatory effects, isoquercitrin was treated with lipopolysaccharide, which induces proinflammatory factors in Raw 264.7 macrophage cells. Proinflammatory effects were measured by real-time polymerase chain reaction and Western blotting as well as enzyme-linked immunosorbent assay. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to define the isoquercitrin concentration nontoxic to cells. Nitric oxide (NO) production, prostaglandin E2, inducible NO synthase, cyclooxygenase-2 (COX-2), and nuclear factor-κB p65 protein expression decreased in a concentration-dependent manner by isoquercitrin. mRNA expression of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, monocyte chemoattractant protein-1, and prostaglandin E synthase 2 (PTGES2) as proinflammatory factors significantly decreased. PTGES2, which was stimulated by COX-2 and involved in PGE2 expression, was inhibited. Therefore, this study rendered isoquercitrin isolated from the newly bred Green ball apple peel as a potential pharmacological alternative to treat inflammation-related diseases. © King Abdulaziz City for Science and Technology 2022.