The determination of antioxidants continues to be interested, since the oxidative damage is thought to be one of the main mechanisms involved in nearly all chronic renal pathologies. A highly sensitive high performance liquid chromatography-electrochemical detection (HPLC-ECD) method was developed for evaluating the antioxidant properties of Salvia miltiorrhiza (Dan Shen). The method was optimized with respect to selectivity and sensitivity. Chromatographic conditions, including mobile phase pH value, buffer concentration, buffer type, organic solvent type, gradient profile and flow rate, were systematically investigated. Low pH value (2.8), low buffer concentration (20 mmol/L NaH2PO4), a shallow water-acetonitrile gradient, and a flow rate of 0.2 mL/min were the determined optimal conditions for the quantitative analysis of aimed five antioxidants from 14 batches of Dan Shen samples. The described method provided a good recovery (>95%), a very wide linear range (up to 104 for all analytes), a good precision (RSDs<4.01%), and a high sensitivity (LOQ of caffeic acid, 1.5 μ g/L). Compared with UV detection, the described ECD method was also more effective for evaluating the antioxidant properties of Dan Shen, as it provided highly selective detection of electro-active antioxidants.
Keywords: antioxidant; gradient elution; herbal medicine (HM); high performance liquid chromatography-electrochemical detection (HPLC-ECD); phenolic compound.