Isolation of chemically well-defined semipreparative liquid chromatography fractions from complex mixtures of proanthocyanidin oligomers and polymers.

•Tens of different tannin fractions were produced from a single plant sample.•New tannin fractions differed significantly from the original sample.•Tannin fractions’ retention time width was 8–30% from original sample.•Proanthocyanidin separation varied between different plant samples.