TLC separation of catechins and theaflavins on polyamide plates

The potential of polyamide as adsorbent for separation of nine compounds — (±)-catechin (DL-C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin gallate (EGCg), theaflavin (TF1), theaflavin 3-gallate (TF2A), theaflavin 3′-gallate (TF2B), and theaflavin 3,3′-digallate (TF3) — was studied. Polyamide TLC plates dried with a hair dryer, application as bands, and development in a horizontal chamber gave the best results. Detection was performed using iron(III) chloride-ethanol reagent. Twofold development with chloroform-methanol 2:3 ( v/v ) as mobile phase resulted in the separation of TF1, TF2A, TF2B, and TF3 from all the other compounds. EGCg, ECg, and EGC were separated but EC and DL-C were not separated from each other. The best mobile phase for each of the compounds is reported. The best separation of the five main catechins (EC, DL-C, EGC, ECg, and EGCg) was achieved by use of n -butanol-acetone-acetic acid 5:5:3 ( v/v ). In addition, separation of the flavonols myricetin, quercetin, kaempferol, and rutin and the phenolic acids gallic acid, chlorogenic acid, and caffeic acid was achieved by twofold development with chloroform-methanol 2:3 ( v/v ). The applicability of the method was checked by screening of extracts of green, black, oolong, and pu-erh tea.