Abstract

Hot water extracts (HWEs) from Pinus densiflora and Pinus thunbergii, two major Pinusspecies in Korea, and Pycnogenol^® (PYC), a standardized Pinus pinaster bark extract, were fractionated to yield ethyl acetate (EAF) and proanthocyanidin (PAF) fractions for determination of total phenolic (TP) and proanthocyanidin (PA) content, and antioxidant activity. The TP and PA contents, the PA/TP ratio, and the antioxidant activity from the HWE, EAF and PAF were all in the order of P. densiflora > P. pinaster > P. thunbergii. The mean degree of polymerization (mDP) by acid catalysis in the presence of excess phloroglucinol were similar in all three pine bark EAFs (3.51 to 3.69), but were quite variable in the other fractions (in PAFs, 5.56 (P. thunbergii) to 7.49 (P. densiflora); in HWEs, 4.85 (P. densiflora) to 6.14 (P. pinaster)). However, the PA structures determined by ¹³C NMR analysis with PAFs were similar for all three Pinus species with respect to the ratio of procyanidin and prodelphinidin and C2-C3 stereochemistry. From the aforementioned results, we could suggest that the bark from P. densiflora had more beneficial characteristics than the well-known Pycnogenol^®.

Key words: Antioxidant activity, pine bark, Pinus densiflora, Pinus thunbergii, proanthocyanidin, Pycnogenol^®  

Abbreviation

ABTS, 2,2'-Azinobis (3-ethylbenzothiazoline-6-sulphonic acid); CE, (+)-catechin equivalents; DP, degree of polymerization; EAF, ethyl acetate fraction; HWE, hot water extract; mDP, mean degree of polymerization; mMW, mean molecular weight; NMR,nuclear magnetic resonance; PA, proanthocyanidin; PAF, proanthocyanidin fraction; PC, procyanidin; PD, prodelphinidin; PYC, Pycnogenol^®; TP, total phenolic.