Aimed at investigating the concentrations and taste contribution of the oak-derived ellagitannins castalagin and vescalagin as well as their transformation products acutissimin A/B, epiacutissimin A/B, and beta-1-O-ethylvescalagin in red wine, a highly sensitive and accurate quantification method was developed on the basis of LC-MS/MS-MRM analysis with matrix calibration. Method validation showed good recovery rates ranging from 102.4 +/- 5.9% (vescalagin) to 113.7 +/- 15.2% (epiacutissimin A). In oak-matured wines, castalagin was found as the predominant ellagitannin, followed by beta-1-O-ethylvescalagin, whereas the flavano-C-ellagitannins (epi)acutissimin A/B were present in significantly lower amounts. In contrast to the high threshold concentration levels (600-1000 micromol/L) and the puckering astringent orosensation induced by flavan-3-ols, all of the ellagitannin derivatives were found to induce a smooth and velvety astringent oral sensation at rather low threshold concentrations ranging from 0.9 to 2.8 micromol/L. Dose/activity considerations demonstrated that, among all the ellagitannins investigated, castalagin exclusively exceeded its threshold concentration in various oak-matured wine samples.