[Exploration on feasibility of introducing bioassay method into quality evaluation of Chinese herbal medicines by studying on the correlation between antioxidant activity of Prunella vulgaris and its total phenolic acids content for example].

This paper aims to investigate the correlation between the antioxidant activity of Prunella vulgaris and its total phenolic acids content by measuring the antioxidant activity of different sources and different organs of P. vulgaris and the total contents of protocatechuic acid, protocatechuic aldehyde, caffeic acid, salviaflaside and rosmarinic acid in these samples. Using the 50% methanol extract of P. vulgaris samples as the research object, DPPH method and HPLC method were used respectively to determine the antioxidant activities and the total contents of the above-mentioned five analytes in P. vulgaris samples. 0.5 mL of 50% methanol extract of P. vulgaris reacts with 0.1 mmol•L⁻¹ DPPH ethanol solution for 60 min, then the absorbance of the reaction solution was measured at 517 nm, scavenging rate and IC₅₀ values were calculated by the absorbance and the sample concentration for evaluating the antioxidant activity. HPLC analysis was made on a C₁₈ Epic column, with acetonitrile-0.1% formic acid aqueous solution as mobile phase (gradient elution), and the detection wavelength was set at 280 nm. The correlation between the antioxidant capacity of different habitats and different organs of P. vulgaris and the total contents of five kinds of phenolic acids was analyzed by partial least squares method. The reaction dose-response range of 50% methanol extract of P. vulgaris with 0.1 mmol•L⁻¹ DPPH ethanol solution was 0.300-1.65 g•L⁻¹. When the quantities of potocatechuic acid, protocatechuic aldehyde, caffeic acid, salviaflaside and rosmarinic acid were respectively in 0.007 84-0.980, 0.011 5-1.44, 0.008 64-1.08, 0.080 0-1.00 and 0.079 8-0.998 μg range, their quantities were in good linear relationship with the corresponding peak areas. The average recovery of 5 components were 97.76%, 96.88%, 100.3%, 102.1%, 104.5%, with RSD of 1.8%, 1.6%, 1.7%, 1.6% and 1.7%, respectively. In a certain range of crude drug quantity, the antioxidant activity of each organ of P. vulgaris and total phenolic acids content inside has a good linear correlation. Therefore, in certain quality range of crude drug, DPPH bioassay combined with HPLC content determination can be used for the quality control of P. vulgaris, as is a new method for the quality control of P. vulgaris.