Optimization of extraction for total flavonoids from olive fruit and its changes at different ripening stages

Response surface methodology was employed to optimize the extraction process of total flavonoids in fresh olive fruit assisted by ultrasonic. And the contents of total flavonoids in picual, frantoio, koroneiki, kaliniot, ezhi, yuntai, pendolino and coratina with six maturities were measured. The aim of the extraction process was to examine the extraction parameters such as solid-liquid ratio, methanol concentration, ultrasonic temperature and ultrasound time, and to obtain the best possible combinations of these parameters for maximizing extraction yield of total flavonoids through response surface methodology (RSM) on the basis of single factor experiments. The results showed that the optimal extraction conditions were as follows : solid- liquid ratio1∶23 (g/m L) , methanol concentration 80%, ultrasonic temperature 48℃, ultrasonic time 30 min. Under this optimum condition, the yield of total flavonoids in olive fruit was 0.8567mg/g. The contents of total flavonoids in eight olive varieties with maturity increasing had slight increase after an initial decline. The highest yield of total flavonoids was ‘koroneiki' (3.9042mg/g) at the first maturity, and the lowest one was ‘yuntai' (0.7189mg/g) at the fourth maturity. The yield of total flavonoids in ezhi and coratina were significantly higher than other varieties after the third maturity.