Degradation of polymeric polyproanthocyanidins from black chokeberry by microwave-assisted nucleophilic technique of sulfite/catechin: Reaction kinetics, antioxidation and structural analysis

•Polyproanthocyanidins was degraded by microwave-assisted nucleophilic techniques.•The increasing process parameters were favorable for the degradation reaction.•The degradation kinetics conformed to the random first-order degradation model.•The antioxidation activity of polyproanthocyanidins were improved.•The Mw distribution was narrower, and the compositions were more single.