Optimization of conversion of diospyros lotus l. Myricitrin to Myricetin by citric acid treatment

Citric acid treatment conditions for converting Diospyros lotus leaves to myricetin were optimized using the response surface methodology. The contents of myricitrin and myricetin in extracts of Diospyros lotus leaves were measured using high performance liquid chromatography (HPLC). From several organic acids screened, citric acid produced the highest content of myricetin, and was therefore selected for the conversion of myricitrin from Diospyros lotus leaf extracts. The treatment method of adding citric acid was optimized by the response surface methodology (RSM) using the Box-Behnken design (BBD) with three variables: molar concentration of citric acid (X1: 50∼150 mM), reaction temperature (X2: 85∼95°C) and reaction time (X3: 3∼7 h). RSM analysis revealed that the content of myricitrin and myricetin was highly impacted by the citric acid concentration, whereas reaction temperature had the lowest effect. To verify accuracy of the prediction, the myricetin content was determined under optimal conditions, and the result obtained (1,224.99 mg/100 g DLP) was similar to those predicted. Based on these results, we propose the use of citric acid treatment to increase the yield of myricetin from Diospyros lotus leaves.