According to national surveys, 7.5% of the US population reports using botanical dietary supplements (DSs), which may or may not be labeled for their bioactive content. As part of the Botanical initiative for the Dietary Supplement Ingredient Database (DSID), a pilot study of green tea (GT) DSs was designed to chemically evaluate their levels of flavan-3-ols or catechins, especially epigallocatechin gallate (EGCG). The goal was to evaluate analytical methods for individual catechins and examine the relationships between label claims and analytical results for EGCG and total catechins. Two lots of 32 DSs containing GT as the only or primary botanical were purchased in various market channels and sent for analysis to three laboratories experienced with the analysis of GT. The laboratories used reversed-phase high-performance or ultra-high performance liquid chromatography with either ultraviolet absorbance or mass spectrometric detection. Quality control results from all three laboratories showed good agreement with certified values provided by several GT Standard Reference Materials. The analytical data revealed a wide range of levels for individual and total catechin content among the products tested. DSs providing label information for EGCG content had significantly higher EGCG content as compared to DSs without EGCG claims (298± 48 vs. 114 ± 26 mg/day; mean ± SE, n=18 and 14, respectively). As required by law, all analyzed DSs provided the weight of GT leaf/extract on the label. However, this information did not predict analytically determined phytochemical content. At the most common labeled level (500 mg of leaf/extract per serving), a wide range (0.5 – 309.5 mg/serving) of EGCG content was found (n=9). Statistical analysis did not indicate a laboratory effect on catechin measurements. Thus, methods utilized by two commercial and one research laboratory provided consistent results suitable for including in our analytical database.

Botanical initiative for the Dietary Supplement Ingredient Database (DSID): Interlaboratory trial to assess methods for catechins in green tea dietary supplements

254th National Meeting (2017)

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