Effects of picking time and drying methods on contents of eight flavonoids and antioxidant activity of leaves of Diospyros lotus L.

The leaves of Diospyros lotus L. have many bioactivities such as antioxidant, liver protection and anti-inflammation, in which flavonoids are the main active components. In the study, high performance liquid chromatography (HPLC) method was established to simultaneously determine the contents of eight flavonoids, including myricetin, quercetin and their monoglycoside in the Diospyros lotus L. leaves. The methodological verification showed that the developed method had good linearity, precision, accuracy and reproducibility. During the leaves of Diospyros lotus L. picked from April to October, the contents of eight flavonoids in the samples picked in May were significantly higher than those in other times, and myricitrin content was highest. The total amount of eight flavonoids in freeze-dried samples was significantly higher than those of samples processed by shadow-dried at room temperature and oven-dried at 40 °C. Antioxidant activity of the sample was significantly affected by the picking time and drying method. The antioxidant activities were linearly correlated with the contents of the total flavonoids and myricitrin (Mytr), indicating that Mytr was the main antioxidant ingredient of sample. In a word, the paper lays a foundation for the qualitative and quantitative analysis of eight flavonoids in the leaves of Diospyros lotus L., the preparation of active ingredients and the study on the quality standards of the leaves.