CATECHINS AND METHYLXANTHINES IN TWENTY-THREE BLACK TEA INFUSIONS BY HPLC: CORRELATIONS WITH ASTRINGENCY
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Abstract
Simultaneous detection of flavanols [catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechingallat (ECG), epigallocatechingallate (EGCG)], gallic acid (GA), theogalline, methylxanthines (caffeine, theobromine, theophylline) were performed on 23 black tea infusions. A hypersil-ODS column (4.6 mm I.D. x 250 mm) with methanol: distilled water: formic acid (19.5:80.2:0.3, v:v:v) as a mobile phase was used for optimizing the RP-HPLC separation (R(2)=0.9997). Total flavanols varied from 1.423 to 12.051 mg 100 mg(-1) whereas EGCG was the major catechin in all of the infusions (0.356-5.972 mg 100 mg(-1)) (p<0.01). Caffeine levels were high (4.002-8.657 mg 100 mg(-1)) followed by theobromine and theophylline (p<0.01). Black tea contained 0.134-1.392 mg/100 mg of GA, and 0.156-1.241 mg 100 mg(-1) of its ester theogalline. An 8-member trained sensory panel judged black tea infusions for astringency. The correlations between the total catechins and astringency (y=1.675+6.631 In X) (R(2)=0.9551) were extremely high at the 95 percent confidence level (X=total catechin, y=astringency) and total interactions on astringency were obtained.