Inhibition of the NLRP3 Inflammasome by a Quercus Serrata Extract and Isolation of the Component Compounds for the Treatment of Arthritis

Quercus serrata belongs to the Fagaceae family. There are 600 known species of Quercus worldwide. Q. serrata is distributed nationally in Korea, Japan, and China and grows to a height of 10–15 m. It exhibits a light grey bark with longitudinal furrows; the leaves are 6–12 cm long and 2.5–5 cm wide. The Quercus genus reportedly exhibits several types of bioactivity, including antioxidant, anti-inflammatory, antifungal, antimicrobial, and anticancer activity. Additionally, it has been reported that Quercus produces diverse phytochemicals, including tannins, flavonoids, and triterpenoids. Herein, we describe the column chromatographic isolation of five compounds from a Q. serrata extract. The compounds included caffeic acid (1), myricetin-3-O-cellobioside (2), phloroglucinol (3), (S)-2,3-HHDP-D-glucopyranoside (4), and pedunculagin (5). We assessed the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity, antioxidant activity, NLR family pyrin domain-containing 3 (NLRP3) inflammasome (including NLRP3, ASC, and caspase-1) inhibitory effects, and collagenase inhibition activity of the Q. serrata extract and its constituent compounds. Our results indicated that the Q. serrata extract and the isolated constituent compounds showed inhibitory activity with reference to nitric oxide production, inflammasome component expression, and collagenase activity. Our findings imply that the Q. serrata extract and the isolated constituent compounds are potential candidates for the treatment of inflammatory diseases such as arthritis.