CONIFER SEED CONE PROANTHOCYANIDIN POLYMERS - CHARACTERIZATION BY C-13 NMR-SPECTROSCOPY AND DETERMINATION OF ANTIFUNGAL ACTIVITIES

Proanthocyanidin polymers (condensed tannins) in extracts from Picea glauca, Pinus banksiana, Pinus nigra, Pinus ponderosa, and Pinus taeda seed cones were isolated by chromatography over Sephadex LH-20 and characterized by C-13 nuclear magnetic resonance (NMR) spectroscopy. Ranging in molecular weight (MW(n)) from 1520 to 2460, the seed cone proanthocyanidins were comprised primarily of procyanidin monomer units with the 2,3-cis stereochemistry predominating in the heterocyclic rings. Incorporated into agar media, a proanthocyanidin polymer preparation inhibited the growth of fungal cultures of Ceratocystis coerulescens and Schizophyllum commune but not Trametes versicolor. However, under conditions more representative of those found in nature, the polymer preparation did impart significant decay resistance to T. versicolor in wood test specimens normally susceptible to decay by this fungus. It is apparent from these results that proanthocyanidin polymers contribute to the natural resistance of conifer seed cones to fungal degradation.