AbstractA simple and efficient method for the purification of oligomeric proanthocyanidins (LOPC) from degreased Larix gmelinii bark was developed. The purity of LOPC was increased from 51.7% to 92.2%, and the cumulative recovery rate was 97.0%. The reversed phase high performance liquid chromatography-mass spectrum (RHPLC-MS) analysis indicated that the percentage contents of catechin (CA), epicatechin (EC), and procyanidin B1 (PB1) in purified LOPC (P-LOPC) were 5.05%, 2.02%, and 0.71%, respectively. The percentage contents of catechin and procyanidin B1 were noticeably higher than those obtained from grape seed extract (2.77% and 0.61%). The average degree of polymerization of P-LOPC was found to be 2.66. The matrix-assisted laser desorption ionization-time of flight/mass spectrum (MALDI-TOF/MS) analysis demonstrated that the dimer was the major component of purified LOPC and the distribution range was from dimer (m/z 713) to decamer (m/z 3016.6). The IC50 values of P-LOPC against DPPH• (1,1-diphenyl-2-picryl-hydrazyl), OH• (hydroxy radical), and ABTS+ (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt) were 76.4±3.82, 7.92±0.40, and 2.4±0.12. Purified LOPC exhibited more excellent physiological activity than VC (vitamin C), TBHQ (tert-butyl hydroquinone), and pine bark extract.