GRAPE SEED PROANTHOCYANIDIN EXTRACT CHELATES IRON AND ATTENUATES THE TOXIC EFFECTS OF 6-HYDROXYDOPAMINE: IMPLICATIONS FOR PARKINSON'S DISEASE

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ABSTRACT Proanthocyanidins are potent antioxidants associated with protection against diseases. We tested the reducing capacity, iron chelating activity, and anti-auto-oxidation ability of grape seed proanthocyanidin extract (GSPE). The mechanisms underlying GSPE attenuation of oxidative processes induced by 6-hydroxydopamine (6-OHDA), a neurotoxin used to induce Parkinson's disease, were investigated in cell-based systems. At high concentrations, GSPE (50 µg/µL) was a mild pro-oxidant in a Fenton-type reaction. GSPE (300 µg/mL) was as potent as 30 µM deferoxamine in its iron-chelating capacity, and as efficient as 5 mM ascorbic acid in delaying 6-OHDA auto-oxidation. In PC-12 cell cultures, 100 and 300 µg/mL GSPE significantly protected (P < 0.05) cells from 6-OHDA-induced (400 µM) toxicity. GSPE-induced cytoprotection is enhanced by a nitric oxide synthase inhibitor (NOSI), implying that the cytoprotective effect of GSPE does not require NOS activation. In conclusion, the iron-chelating activity of GSPE minimizes its pro-oxidant activity and delays 6-OHDA auto-oxidation to provide cytoprotection. PRACTICAL APPLICATIONS Parkinson's disease is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons. The recognized pharmacological strategies to prevent or treat Parkinson's disease include the minimization of oxidative stress, iron release and excitotoxicity resulting from excess nitric oxide formation. One of the best ways to delay or prevent the onset of the disease is to improve the biological antioxidant status by providing additional radical scavengers that are not pro-oxidants. The pro-oxidant activity, such as that of the antioxidant ascorbic acid, enhances radical cycling under certain conditions, and therefore may be detrimental. Grape seed proanthocyanidin extracts (GSPEs) are used as a dietary supplement in food products in several countries. Our current report provides evidence that GSPE has limited pro-oxidant activity, presumably because of its iron-chelating abilities, and protects cells from neurotoxic insults. GSPE may be effective as a dietary supplement for prophylactic use against the progressive neurodegeneration seen in Parkinson's disease.