Zulema Piñeiro | PubMed Health

PubMed2004

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.

Catechin↗

PubMed2002

In-line pressurized-fluid extraction-solid-phase extraction for determining phenolic compounds in grapes.

A new method of pressurized-fluid extraction coupled in-line with solid-phase extraction has been used for the extraction of phenolic compounds from grapes. The full extraction method is performed under an inert atmosphere. Five different solvents have been assayed using different extraction pressures and temperatures. Using two extraction stages with two different solvents, water and methanol, quantitative recovery for most of the assayed compounds has been found in the second extract. Only the most polar phenolic compound, gallic acid, was found distributed in both extracts. The application to real samples allows for a clean-up of the extracts. Cinnamic esters like caftaric acid, cis and trans-coutaric acids were found only in the methanolic extract. The reproducibility for the new method was measured using both an inert solid spiked with standards and grapes. Using between 202 and 424 microg of spiked standards, the resulting relative standard deviations were less than 5%, with the exception of gallic acid (RSD=13%). For grapes, the resulting RSD were 11% for trans-coutaric acid, 10% for caftaric acid and 6% for cis-coutaric acid.

Phenols↗