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One of the most popular themes around healthy foods is the emphasis on their anti-oxidant activity. Anti-oxidants remove reactive oxygen from cells, which minimizes damage to the cell. So, having associated “anti-oxidant” with “healthy” for so long, it was surprising to see an article about the anti-cancer properties of the pro-oxidant activity of dietary components.

The paper, a commentary titled “Pro-oxidant activity of dietary chemopreventive agents: an under-appreciated anti-cancer property”, was written by Asfar Azmi and Fazlul Sarkar of Wayne State University in Detroit, and by SM Hadi of Aligargh Muslim University in India. The article was also recommended in F1000Prime, where F1000 Faculty Member Alexandru Grigorescu said “This article is very important for our understanding of cancer biology and prevention and the curative properties of some components of food.”

How does it work, though? How can anti-oxidants and pro-oxidants both be healthy? We spoke to Professor Hadi, who explains the mechanism in the following video:

To summarize, Hadi starts by pointing out that because the anti-oxidant activity of plant polyphenols has several known health benefits, everyone just assumed that the same mechanism caused polyphenols’ therapeutic effects in cancer.

“In addition to anti-cancer properties, plant polyphenols also exhibit various other pharmacological properties, such as anti-cardiovascular disease action and anti-inflammatory properties. Since they were known to be anti-oxidants, their anti-cancer effects were also attributed to their anti-oxidant action. Consequently, the pro-oxidant anti-cancer activity of plant polyphenols remained under-appreciated.”

But plant polyphenols are also pro-oxidants, that catalyse DNA degradation in the presence of copper ions.

“Copper is an important metal ion present in chromatin, and is closely associated with DNA bases. Of particular interest is the observation that these phenols induce cell death in various cancer cell lines, but not in normal cells. It was shown long back that copper levels are considerably elevated in serum and affected tissues of cancer patients. More than a decade back we had proposed that it is the mobilisation of elevated copper levels in cancer cells, and consequent pro-oxidant degradation of cellular DNA that accounts for their anti-cancer properties.”

In their F1000Research commentary, Hadi and colleagues give a brief overview of the pro-oxidant activity of plant polyphenols. In the video interview, he summarizes the conclusions and their proposed model.

“The chemopreventive anti-cancer properties of plant polyphenols can be ascribed to their anti-oxidant action as they are able to scavenge oxygen radicals. (…) However, the therapeutic properties of polyphenols cannot be attributed to such an action. The mechanism proposed by us would explain both the chemopreventive, as well as therapeutic properties of plant polyphenols.”

Hadi’s work is in line with a paper by James Watson, published earlier this year in Open Biology, which also emphasizes pro-oxidant activity as an important component of cancer therapy.

References:
Azmi A.S., Sarkar F.H. & Hadi S. (2013). Pro-oxidant activity of dietary chemopreventive agents: an under-appreciated anti-cancer property [v1; ref status: indexed, https://f1000r.es/15s] , F1000Research, 2 DOI: 10.12688/f1000research.2-135.v1

Grigorescu A. DOI: 10.3410/f.718106504.793483715

Watson J. (2013). Oxidants, antioxidants and the current incurability of metastatic cancers, Open Biology, 3 (1) 120144-120144. DOI: 10.1098/rsob.120144