Chilean researchers discover in the peel of the onion the most powerful antioxidant known so far

“We discovered an antioxidant in the peel of the onion, whose action is exerted at the nanomolar level. This means that the molecule discovered acts in human cells at extremely low concentrations, its potency being -therefore- superior to practically any other antioxidant molecule so far known. ”
This is how Hernán Speisky, director of the Antioxidant Laboratory of the Institute of Nutrition and Food Technology (INTA) of the University of Chile, explains the recent finding of the extraordinary properties of the onion peel made together with the researcher Jocelyn Fuentes, head of the Antioxidant Analysis Laboratory of the same academic unit.
The research began in 2017, in the middle of the doctoral thesis process of Professor Fuentes, where the proposed objective was to analyze what happened to antioxidants when they oxidized, particularly polyphenols.
This is how, says the professor, “we found and identified in the skin of the onion that the benzofuranone molecule (BZF), the oxidized form of the polyphenol quercetin, has an antioxidant potency 1,000 times higher than that of the same unoxidized polyphenol.”
Experimental research models allowed to establish that the administration of very low doses of an extract (prepared from the dry skin of onions) protected experimental animals against damage to their intestinal mucosa and against the alteration of the barrier function of their intestine induced by pro-oxidant agents that erode the mucosa of the gastrointestinal tract, such as NSAIDs (non-steroidal anti-inflammatory drugs) or alcohol.
Also, and given that the alteration of the intestinal barrier function is a condition that is also frequently associated with obesity and diabetes, the researchers explain that the discovery made opens the possibility that the extract developed is eventually of enormous therapeutic utility in such conditions.
Pioneering studio
The studies carried out so far are pioneering, and show that the compound (BZF), naturally present in the dry skin of the onion, behaves in the cells as the most powerful antioxidant and anti-inflammatory so far known.
The research focused on onions, after having studied more than twenty fruits and vegetables that are recognized as rich in the polyphenol quercetin.
“We started looking for what foods quercetin could be found in its oxidized state and we came to the onion, but the interesting thing was that we did not find it in its pulp, but only in its skin, and specifically, in the outermost dry layers of it. We also saw it in the dry skin of the red onion and shallot, which are a variety of small onions that are consumed a lot in France,” says Professor Fuentes.
Dr. Speisky explains that the research was initiated with the aim of “questioning the scientific assumption that when an antioxidant is oxidized it loses its antioxidant properties. And for this we have been working primarily on a type of antioxidants that are called flavonoids (a class of polyphenols), which are the most abundant natural antioxidants in human food.”
In this line, he adds that “using cells of the epithelium of the human intestine exposed to free radicals or generating agents of these species (such as NSAIDs or alcohol), we show that the damage produced at both the cellular and molecular level is totally prevented in the presence of the onion skin extract, as well as by the addition of purified BZF concentrations added to the same concentration that was present in the extract. Interestingly, the concentrations or doses of benzofuranone needed to induce total protection of these cells turn out to be 1,000 times lower than those required by the flavonoid (quercetin) that originates said benzofuranone.”
In addition, he says that they supported the above “demonstrating that very low doses of the extract fully protect the intestinal mucosa of experimental animals against oxidative damage and against the loss of intestinal barrier function induced by NSAIDs.”
Such findings have recently been published in journals that currently enjoy the greatest scientific recognition in the area of antioxidants and food chemistry.
Future challenges
Usually, when we handle an onion for consumption in the kitchen, we remove and then discard the meatscara to use only the inner white part. So, it is worth asking, in what way can we use or consume this element in our daily diet? Specialists are clear in clarifying that this corresponds to a second stage and that it is not yet possible to establish its direct consumption as a healthy practice.
“We have been advancing not only in a greater characterization of the potential uses of BZF, but also in the development of a nutraceutical preparation containing the onion skin extract standardized in terms of BZF. And although we are not yet in a position to suggest its use or lower doses in humans, initiating clinical studies with the extract is part of our next steps to follow,” says Professor Fuentes.
For his part, Speisky points out that “the interest in antioxidants arises from the wide recognition that the intake of foods rich in molecules – which have the ability to extinguish or neutralize free radicals – contribute substantively to reduce the risk of developing various chronic non-communicable diseases, such as those that affect the cardiovascular system, the central nervous system and various forms of cancer.”

Original source in Spanish