Spectrum-effect relationship of antioxidant activity in Vitex negundo var. cannabifolia leaves based on HPLC-ECD

In order to study the spectrum-effect relationship between fingerprint and antioxidant activity of the leaves of Vitex negundo var. cannabifolia, the fingerprints of 18 batches of V. negundo var. cannabifolia leaves were established by high performance liquid chromatography-electrochemical detection (HPLC-ECD), and the cluster analysis of medicinal materials from different sources was performed simultaneously. The main phenolic compounds from V. negundo var. cannabifolia leaves were identified and determined. The contents of total phenolics and total flavonoids in V. negundo var. cannabifolia leaves were analyzed, and the antioxidant activities in vitro were evaluated by the methods of DPPH radical scavenging capacity, ABTS radical scavenging capacity, oxygen radical absorbance capacity and ferric ion reducing ability power. The spectrum-effect relationships of V. negundo var. cannabifolia leaves were analyzed by Pearson correlation analysis, gray relational analysis and partial least square regression analysis. The results were as follows: (1) The fingerprints of V. negundo var. cannabifolia leaves were established with 21 common peaks and a total of 10 peaks were identified. The order of content was chlorogenic acid > isoorientin > luteoloside > isovitexin > isochlorogenic acid A > isochlorogenic acid C > protocatechuic acid > orientin > isochlorogenic acid B > neochlorogenic acid. The similarity among the samples from different producing areas was high, and the values were ranged from 0.816 to 0.983. (2) The results of the cluster analysis showed that the content of the compounds had a certain influence on the classification and the samples from different sources were divided into three categories, among which the samples from the south and the north were different. (3) The contents of total phenolics and total flavonoids in V. negundo var. cannabifolia leaves were 15.82 to 61.83 mg·g-1 and 27.85 to 157.65 mg·g-1, respectively, and the antioxidant activity of all samples from V. negundo var. cannabifolia leaves existed differences. (4) The spectrum-effect relationship indicated that the antioxidant activity of V. negundo var. cannabifolia leaves was the result of the synergistic effect of many compounds, and compounds such as peak 9 (isoorientin), peak 4 and peak 5 (chlorogenic acid) made the greatest contribution to the antioxidant activity of V. negundo var. cannabifolia leaves. V. negundo var. cannabifolia has good antioxidant activity, and the main activity indexes are isoorientin and chlorogenic acid. This study can provide a reference basis for the screening and quality control of antioxidant components in V. negundo var. cannabifolia.