A few days ago, I posted about a 1 September Cancer Research paper showing that a muscadine grape skin extract (MSKE) lacking resveratrol had activity in killing prostate cancer cells. I’ve finally had a chance to look at the paper. The study was very well-done by Dr Jeffrey Green’s group at the US National Cancer Institute with colleagues at Georgia, Texas, USDA, and George Washington University. The studies showed that the grape skin extract (at 10-20 μg/mL) had cytotoxic activity against progressively tumorigenic prostate cell lines but had no effect on normal prostatic epithelial cells grown in culture.
However, there are some notable drawbacks before people go off buying muscadine grape skin extract to prevent or treat prostate cancer – I mention this because some readers have asked where they can obtain the extract. First of all, the pulverized, powdered grape skins had to be dissolved in alcohol to release the active constituents. From the paper:
Polyphenolic compounds from the dried and pulverized muscadine grape skin were extracted with 50% ethanol/water at a nominal ratio of 9:1 (v/w) by stirring with a magnetic stir bar for 1 h at room temperature. The slurry was allowed to settle for 24 h, and the supernatant was passed through a 0.2 μmol/L [sic; should be 0.2 μm] membrane filter funnel (Nalgene) and collected under a vacuum.
So, ingesting grape skin extract is not the same as extracting it in what is essentially 100 proof vodka. Even with that preparation, we have no idea how much of the extract would be required to produce peripheral blood concentrations consistent with those that killed prostate cancer cells in culture.
Moreover, we don’t know if this extract will kill or slow the growth of human prostate tumors propagated in immunocompromised mice, the gold-standard for assessing potential human anti-tumor activity. I’m certain that Dr Green’s group is pursuing these studies but the data are not yet available.
For researchers interested in experimenting with this unique, “no-resveratrol” grape skin extract, the supplier for this study was Muscadine Products Corporation of Wray, GA.
However, prostate cancer patients are warned that it is far, far too early to think about using the grape skin powder to treat or prevent the disease – it must be extracted, we don’t know if it works in a whole animal, we don’t know if the active components are metabolized too quickly and, if metabolism wasn’t an issue, we certainly don’t know how much to use to treat or prevent prostate cancer.
As follows any such in vitro report, manufacturers are bound to promote this product to cancer patients. So beware and consider yourself too well-informed to be duped.