More relevant research needed for antioxidants, says expert

By Stephen Daniells

- Last updated on GMT

Related tags: Polyphenols, Flavonoid, Antioxidant

Antioxidants should be the focus of more relevant research,
especially for the high doses used in dietary supplements,
according to an editorial in the journal Molecular
Pharmaceutics.

Ming Hu from the University of Houston issues "a call to arms" for more relevant research into the bioavailability and utilisation of the antioxidants, particularly polyphenols, in order to help "the successful development of polyphenols as chemopreventive agents in the future"​. A vast body of epidemiological studies has linked increased dietary intake of antioxidants from fruits and vegetables to reduced risks of a range of diseases including cancer, cardiovascular disease and diabetes. "However, these types of research are often carried out on animals, and their effects on humans remain uncertain. A critically important scientific question is then: are these flavonoids and polyphenols as effective as people believe?"​ wrote Hu. Indeed, insufficient research has been done with respect the bioavailability of these compounds, and possible interactions with pharmaceuticals, he said. "Because these agents are targeted for disease prevention, oral administration is the only viable route, except for topical application on external organs such as skin,"​ he wrote. "For polyphenols to become bioavailable, the following barriers must be overcome: solubility, permeability, metabolism, excretion, target tissue uptake, and disposition."​ Moreover, animal studies have suggested that the bioavailability of typical polyphenols is around 10 per cent or less, but this can range from two to 20 per cent. "There is an urgent need to perform systematic studies to demonstrate how changes in polyphenol structures affect solubility and dissolution rates and how various pharmaceutical excipients may be used to improve their dissolution rate,"​ said Hu. The Houston-based researcher also highlights the need for mechanistic studies to determine the activities and functions of related compounds, and how the metabolites of the polyphenols are transported across biological membranes. This last point is "critically important,"​ he said, "assuming some metabolites are active or can be converted into active parent compounds at target organs."​ Another point of critical importance, said Hu, is the potential of the polyphenols to interact with pharmaceuticals and cause adverse events. This was particularly an issue with soy isoflavones and the potential to stimulate the growth of cancer cells in vitro​ in the absence of hormone. "More bioavailable or highly bioavailable polyphenol formulations or derivatives are very desirable because they will be easier to develop and less costly to test,"​ he concluded. Source: Molecular Pharmaceutics​ Volume 4, Number 6, Pages 805-806 "Commentary: Bioavailability of Flavonoids and Polyphenols - Call to Arms" ​Author: M. Hu

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