Neuroprotective Effects of Korean Red Pine (Pinus densiflora) Bark Extract and Its Phenolics

Korean red pine (Pinus densiflora) is one of the major Pinus species in Korea. Red pine bark is removed prior to the chipping process in the wood industry and discarded as waste. However, red pine bark contains a considerable amount of naturally occurring phenolics, including flavonoids, and therefore may have a variety of biological effects. In this study, we investigated if Korean red pine bark extract (KRPBE) could protect neuronal PC-12 cells from oxidative stress and inhibit cholinesterase activity. Analysis of reversed-phase high-performance liquid chromatography results revealed four phenolics in KRPBE: vanillin, protocatechuic acid, catechin, and taxifolin. The total phenolic and flavonoid contents of KRPBE were 397.9 mg gallic acid equivalents/g dry weight (DW) and 248.7 mg catechin equivalents/g DW, respectively. The antioxidant capacities of KRPBE measured using ABTS, DPPH, and ORAC assays were 697.3, 521.8, and 2,627.7 mg vitamin C equivalents/g DW, respectively. KRPBE and its identified phenolics protected against H₂O₂-induced oxidative cell death in a dose-dependent manner. Acetylcholinesterase and butyrylcholinesterase, which degrade the neurotransmitter acetylcholine to terminate neurotransmission in synaptic clefts, were inhibited by treatment with KRPBE and its identified phenolics. Taken together, these results suggest that KRPBE and its constituent antioxidative phenolics are potent neuroprotective agents that can maintain cell viability under oxidative stress and inhibit cholinesterase activity.