Effect of Pinus radiate bark extracts with different molecular weight distributions on cell growth of NIH/3T3 fibroblasts and dendrite retraction of B16 melanoma cells

Abstract

Hot water extract (HWE) of Pinus radiata bark was separated into monomeric polyphenol (MPP), oligomeric proanthocyanidin (OPA), and polymeric proanthocyanidin (PPA) fractions by monitored chromatography using a Sephadex LH 20 column and an UV detector at 250 nm. The effects of these fractions on NIH/3T3 fibroblasts and B16 melanoma cells were examined by evaluating cell viability, melanogenesis (melanin content), morphological changes, and tyrosinase inhibitory activity. The polyphenolic fractions had a proliferation effect on fibroblasts, with cell growth increasing significantly (P < 0.01) even at the high concentration of 1250 μg/ml. At 125 μg/ml, HWE, MPP, and OPA had no effect on melanogenesis, whereas PPA significantly upregulated melanogenesis (P < 0.05). Melanogenesis was significantly upregulated in melanoma cells treated with these fractions at the high concentration of 600 μg/ml (P < 0.01). B16 melanoma cells cultured with the proanthocyanidin (PA)-rich fractions (HWE, OPA, and PPA) showed marked dendrite retraction, leading to significant morphological transformation. OPA in particular showed colored adhesion on the surface of melanoma cells. All four fractions significantly inhibited mushroom tyrosinase activity when compared to arbutin and ascorbic acid 2-glucoside (P < 0.05). The tyrosinase inhibitory activity of OPA and PPA did not differ significantly (P = 0.11), indicating that the inhibitory effects had a low correlation with molecular weight distribution. The inhibition kinetics of PPA determined using a Lineweaver-Burk plot indicated that PPA is a noncompetitive inhibitor of l-3,4-dihydroxyphenylalanine oxidation by mushroom tyrosinase.