Protocatechuic acid from Alpinia oxyphylla against MPP+-induced neurotoxicity in PC12 cells

An ethyl acetate extract of Alpinia oxyphylla was found to possess neuroprotective activity against 1-methyl-4-phenylpyridinium ion (MPP+) induced apotosis and oxidative stress in cultured PC12 cells. From the extract, a phenolic compound was isolated through bioassay-guided fractionation and identified as protocatechuic acid (PCA) by IR, MS, and 1H and 13C NMR spectroscopy. It was the first time which was isolated from the kernels of A. oxyphylla. Exposure of PC12 cells to 1 mM MPP+ may cause significant viability loss and apoptotic cell death. PCA stimulated PC12 cellular proliferation and markedly attenuated MPP+-induced apoptotic cell death in a dose-dependent manner. By observing the nuclear morphological changes and flow cytometric analysis, PCA showed its significant effect on protecting PC12 cells against MPP+-induced apoptosis. Meanwhile, PCA enhanced the activities of superoxide dismutase (SOD) and catalase (CAT) in PC12 cells. In addition, PCA also dose-dependently reduced the hydrogen peroxide (H2O2)- or sodium nitroprusside (SNP)-induced cell death in PC12 cells. The results suggest that PCA may be one of the primary active components in the kernels of A. oxyphylla and provide a useful therapeutic strategy for the treatment of oxidative stress-induced neurodegenerative disease such as Parkinson’s disease.