Optimizing the Salt-Processing Parameters of Achyranthes bidentata and Their Correlation with Anti-Osteoarthritis Effect

Abstract

Achyranthes bidentata is always salt-processed before being prescribed for treating osteoarthritis. Yet the salt-processing parameters have not been optimized, and the specific bioactive constituents responsible for the osteoarthritis effect of salt-processed A. bidentata have not been fully elucidated. In this study, a Box–Behnken experimental design was chosen for the optimization of the salt-processing parameters of A. bidentata, including stir-frying time, concentration of brine, and soak time. Meanwhile, HPLC–Q-TOF-MS was utilized to analyze the chemical profiles of various batches of raw and salt-processed A. bidentata. The anti-inflammatory potential of nine batches of both raw and salt-processed A. bidentata was assessed via a cyclooxygenase-2 (COX-2) inhibitory assay. A gray correlation analysis was conducted to correlate the peak areas of the compounds in raw and salt-processed A. bidentata with their COX-2 inhibitory effects. Finally, the optimal salt-processing conditions are as follows: soak time: 29 min; concentration of brine: 1.8%; stir-frying time: 4.4 min. Twenty-nine compounds were identified. Eight compounds were found to have a strong positive correlation with anti-inflammatory activity, as confirmed by the COX-2 inhibitory assay. Notably, this is the first report of the COX-2 inhibitory effects of sanleng acid, stachysterone D, dihydroactinidiolide, N-cis-feruloyl-3-methoxytyramine, 9,12,13-trihydroxy-10-octadecenoic acid, azelaic acid, and dehydroecdysone.