K2s2o8

Formic acid, methanol, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), acetylacetone, NaOH, K₂S₂O₈, and Ehrlich reagent were obtained from Beijing Chemical Plant. Platycodin D, arbutin, platycodin D₃, platycoside E, syringin, chlorogenic acid, baicalin, and luteolin reference products were obtained from China Institute of Pharmaceutical Biological Products Identification. The chromatographically pure acetonitrile and methanol were obtained from J.T. Baker Co., USA. Tyrosinase, l-tyrosine, sodium hyaluronate, and hyaluronate were obtained from Beijing Solebo Technology Co., Ltd. The original 264.7 cells and B16F10 cells were purchased from the Cell Resource Center of the Shanghai Institute of Biological Sciences, China and stored in the laboratory of a medical college affiliated with the Changchun University of Chinese Medicine. Dulbecco's Modified Eagle's Medium (DMEM), fetal bovine serum, and antibiotics (penicillin and streptomycin) were obtained from Gibco USA. Triton X-100, α-MSH, ELISA kit (NO, IL-6, TNF-α), and cell counting kit-8 (CCK-8) kit were obtained from Changchun Baijin Biotechnology Co., Ltd. Pure water was obtained from Wahaha Food Co. Ltd.

All reagents used in the experiment were of analytical grade unless otherwise mentioned. FA (Fig. 1a) was obtained from the Chinese Food and Drug Inspection Institute (Beijing, China). AgNO₃, KIO₄, K₂S₂O₈, KOH, hydrochloric acid, sodium metabisulphite, sodium borate, and EDTA were obtained from Beijing Chemical Reagent Company (Beijing, China). Luminol was purchased from TCI Shanghai (Shanghai, China). Ag(iii) stock solution was prepared in accordance with a previously described method.^{19 (link)} Experimental water was ultrapure water.