Determination of catechins by means of extraction with pressurized liquids.

The technique of extraction with pressurized liquids is applied for extraction of catechin and epicatechin in tea leaves and in grape seeds. The extracts obtained are then analyzed by HPLC. A comparison has been made of the recoveries obtained employing extraction by magnetic stirring, ultrasound-assisted extraction, and extraction with pressurized liquids. In the three extraction systems, four different pure solvents were utilized, namely water, methanol, ethanol, and ethyl acetate. Methanol produced the best results. For this comparison, an initial step was to check the stability of catechins during the process of extraction using pressurized liquids at high temperature (100-200 degrees C). It has been confirmed that recoveries of these two compounds begin to fall, to below 95%, at 130 degrees C and above. Pressurized liquid extraction using methanol as solvent, produces results, in terms of recovery of catechin and of epicatechin, notably higher than any of the other conditions of extraction tested. The duration of the extraction cycle was also evaluated and re-extractions were performed to ensure the full recovery from the samples. It was found that, forcatechin, the R.S.D. of the method is 3.21%, and for epicatechin the R.S.D. was 2.96% (n = 5). The final optimized pressurized liquid extraction method allows for the determination of catechin and epicatechin in diverse types of samples with a rapid (10 min) and reproducible method.