Antioxydant activity, oxidative stability properties of Colza oil, comparison of mechanical agitated and ultrasonic extraction on green tea catechins of Camellia sinensis L.

Ultrasonic extraction “UE” used to optimize the extraction yield of phenolic compounds “PC” from green tea Camellia sinensis L., and compared with mechanical agitated extraction “MAE”.
UE was applied at different times (15, 10 and 5min) and temperatures (25, 60 and 95°C) and MAE was performed at these experimental conditions (15 min, 95°C, 400 rpm). Results demonstrate that the maximum yield of epigallocatechin 3-gallate “EGCG” extracted by UE was significantly (P < 0.05) higher than that obteined using MAE (136 mg/g vs 100 mg/g, respectively). The optimum conditions for the polyphenol compounds “PC” recovery are obtained using UE during 15 min at 95°C (~134.66 mg/g). Four catechins from extracted PC were identified using high-performance liquid chromatography equipped with a diode array detector and liquid chromatography mass spectrometry “HPLC-DAD & LC-MS”: epigallocatechin “EGC”, epicatechin “EC”, epigallocatechingallate “EGCG”, and epicatechin-gallate “ECG”. EGCG is the major compound in polyphenol extracts representing 60 %. The antioxidant capacity of the obtained extracts was also studied. Diphényl-2-pycril-hydrazyl “DPPH” scavenging activity is higher for UE than MAE (~ 90 % vs ~85%). Moreover, the PC obtained by UE added to colza oil had a higher oxidative stability, determined by rancimat than those extracted by MAE method (~30.62 h vs ~21.26 h). Results indicate the suitability of UE method for production of PC as potent antioxidant for stabilization of vegetable oils such as colza oil.