Proanthocyanidins (PACs) are naturally occurring ﬂavonoids possessing health beneﬁcial bioactivities. Their quantiﬁcation often utilizes the 4-dimethylaminocinnamaldehyde (DMAC) spectrophotometric assay with the assumption that molar absorption coeﬃcients (MACs) are similar across the various PAC species. To assess the validity of this assumption, individual PAC monomers and oligomers were examined for their absorbance response with DMAC. Our results have shown that PAC dimers and trimers with interﬂavan linkage variations exhibited diﬀerential absorbance response. Absence of A-type linkage between the terminal and second units in PAC molecule not only impacts absorbance intensity at 640 nm but also elicits a prominent secondary 440 nm absorbance peak. Cranberry (A-type) and cocoa (B-type) oligomeric PACs exhibited diﬀerential absorbance (MACs) relationship with degree-of-polymerization. Thus, PAC structural variations have considerable impact on the resulting MAC. The use of DMAC assay in PAC quantiﬁcation, especially in comparing across speciﬁc oligomers and compositions, should not assume MACs are similar.
Link to Purchase Publication