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Wednesday, September 14, 2016

Florida Muscadine Grapes ... Full of Health Promoting Polyphenols

As muscadine grapes are notable for their highly pigmented, thick skins in which the content of polyphenols is known to be high, research interest in describing these phytochemicals is significant.

One early report had indicated that muscadine grapes contained high concentrations of resveratrol, but subsequent studies have found no or little resveratrol in muscadine grapes. It appears that the initial report overestimated the amount of resveratrol because it relied on a less precise method, which could not distinguish resveratrol from ellagic acid, another polyphenol found in higher concentration in muscadine grapes.

Resveratrol is a polyphenol produced by many plants (including grapes) as a natural antifungal, and is widely thought to be health-promoting. Red wine typically contains between 0.2 and 5.8 mg/L, depending on a range of factors, while white wine has much less. This is because most of the resveratrol in grapes is located in the skin of the grape, and red wine is fermented with the skins of the grape included, allowing the wine to absorb it; by contrast, white wine is fermented after the skins have been removed.

Other muscadine polyphenols include:

  • anthocyanins such as delphinidin and petunidin
  • tannins
  • quercetin
  • flavan-3-ols (catechins, particularly in seeds)
  • gallic acid
  • ellagic acid (particularly in skin)
  • ellagic acid glycosides
  • ellagitannins
  • myricetin (particularly in leaves)
  • kaempferol

The rank order of total phenolic content among muscadine components was found to be seeds >> skins > leaves >> pulp


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