PROCYANIDINS AND POLYPHENOLS OF LARIX GMELINI BARK

Article abstract of DOI:10.1016/S0031-9422(00)84524-0

Key Word Index - Larix gmelini; Pinaceae; bark; catechins; procyanidins; biflavonoids; larixinol.Methanol extracts of Larix gmelini bark yielded (-)-epiafzelechin, (+)-catechin and (-)-epicatechin, dimeric procyanidins B-1, B-2, B-3 and B-4 and oligomeric procyanidins.Chemical degradation of the oligomers using toluene-α-thiol and acetic acid showed the oligomers to have flavan-3-ol terminal units possessing either the 2,3-trans (catechin) or 2,3-cis (epicatechin) stereochemistry, with the former predominating.Likewise the extension units were shown to consist of flavan-3-ol units with 2,3-trans or 2,3-cis stereochemistry in roughly equal proportion.The average degree of oligomerization was calculated as 6-7 and the number average molecular weight as 1700-2000.The structure of the residual procyanidins remaining in the bark after methanol extraction is also briefly commented upon.Larixinol is shown to have an unusual spirobiflavonoid structure and a pathway of biogenesis is proposed.