Validated HPTLC and antioxidant activities for quality control of catechin in a fermented tea (Camellia sinensis var. assamica)

Miang, a Thai traditional fermented tea (Camellia sinensis var. assamica), is exploited as nutraceutical and cosmeceutical ingredients despite limited standardization studies. Thus, this research aimed to develop a simple and rapid method for miang quality control using catechin and high‐performance thin‐layer chromatography (HPTLC) validated according to the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) and the Association of Official Analytical Collaboration (AOAC). The developing solvent consisting of toluene: ethyl acetate: acetone: formic acid (6:6:6:1 v/v/v/v) showed acceptable specificity with R (f) value of 0.54 ± 0.02 and linearity with correlation coefficient of 0.9951. The recovery was 98.84%–103.53%, and the RSD of intra‐ and inter‐day precision was 0.70%–3.00% and 1.93%–4.94%, respectively. Miang ethyl acetate fraction is suggested to be attractive ingredient due to rich catechin (25.78 ± 0.53%), prolonged stability at 40 (◦)C, and strong antioxidants determined by the assays of ABTS (IC(50) = 3.32 ± 0.74 mg/ml), FRAP (89.05 ± 15.49 mg equivalent of FeSO(4)/g), and inhibition of lipid peroxidation (IC(50) = 4.36 ± 0.67 mg/ml).