Condensed tannins: preferential substitution at the interflavanoid bond by sulphite ion

The reaction of loblolly pine (Pinus taeda L.) bark tannins with sodium hydrogen sulphite gave sodium epicatechin-(4β)-sulphonate (1) and sodium epicatechin-(4β→ 8)-epicatechin-(4β)-sulphonate (2) in high yield with only a minor amount of sodium 1-(3,4-dihydroxyphenys)-2-hydroxy-3-(2,4,6-trihdroxyphenyl)-propane-1-sulphonate (3).