Determination of total catechins in tea extracts by HPLC and spectrophotometry.Nat Prod Res. 2009; 23(1):93-100.NP
HPLC and spectrophotometric methods were developed for the determination of total catechins in tea extracts. A comparison was made of the two methods after validation. The HPLC method was carried out using a Hypersil ODS C(18) column and a methanol-0.2% acetonitrile gradient elution. This method showed good resolution of individual catechins, and was found to be precise for the quantification of total catechins (summed individual catechins). The spectrophotometric method was used to monitor the change in absorbance that occurs during the reaction between catechins and vanillin-HCl reagents. The determining wavelength was confirmed as 505 nm, where the catechin-vanillin complex showed peak absorbance. The developed spectrophotometric method performed with varying results, when three calibration curves, respectively based on catechin (C), epicatechin (EC) and epigallocatechin gallate (EGCG), were employed. The C and EC calibration curves resulted in decreased contents of total catechins, while the EGCG calibration curve led to results equivalent to the HPLC assays above, suggesting that a proper choice of standard is necessary for the spectrophotometric determination of total catechins. The two methods can be used for the routine determination of total catechins in catechin-containing products.