Passion of the antioxidant kind

In a study jointly led (1) at the universities of Liège and Sao Paulo, researchers have demonstrated the antioxidant properties of passion fruit by using original research methods. In this way they have laid the foundations for a new approach to the research of vegetable extracts that are endowed with the ability to modulate the potential excesses of antioxidant species and in particular, free radicals in the cell, excesses which can be particularly damaging during inflammatory reactions, in case of infection, accident, muscular trauma etc. 

The interdisciplinary center, CORD (Centre for Oxygen, Research and Development) includes clinicians in human and veterinary medicine as well as researchers in fundamental sciences. “The subject of our research concerns the demonstration of active forms of oxygen from a physiological or pathological point of view. We study the oxidative stress and the metabolism of oxygen based on those active forms of oxygen that are vulgarly and restrictively called free radicals. These active forms of oxygen, mainly produced in vivo by the mitochondria and the leukocytes, play a role in the physiological balance of the cell and inflammation.  The originality of our work resides in finding natural extracts capable of neutralizing these active forms of oxygen, but especially those capable of inhibiting or modulating the activity of enzymes (called “oxidizing enzymes”) which produce them in vivo. These enzymes are especially present in the main type of leucocytes, neutrophils, specialized in the defense of the organism, but also involved in the amplification of the inflammatory response, which makes it interesting to use them as cellular models,” explains its director, Didier Serteyn.

This research is of interest both for human and veterinary medicine, particularly equine veterinary science. Indeed, the horse which is a much more sensitive animal than the cow can die as a result of an excessive inflammatory reaction, a pathological state which corresponds to real oxidative stress.  

When finished, it will help in the perfection of medicines based on antioxidants, which regulate these potential excesses. It is important to note that antioxidants are not always good and that, when they are used to excess, they can provoke an opposite effect to the one sought. As the Swiss doctor Paracelsus (1493-1541) wrote: «In all things there is poison, and there is nothing without poison, only the dose permits something not to be poison». In other words, by reacting with the oxidizing species, the antioxidants can themselves become oxidants. Furthermore, the more oxidizing species there are, the more antioxidants will be required to neutralize them with risks of overdosing. Hence the importance of targeting the modulation effects of vegetable extracts or molecules on the enzymes that are directly at the source of oxidizing species.

Natural extract with active ingredients 

Research has been carried out on numerous plants in order to determine if they can be a source of antioxidants and potentially become future medicines. In this way it has been shown that curcumin, the principal pigment of curcuma (Curcuma longa) possesses antioxidant properties. In practice, the researchers work on natural extracts and develop tools in order to test the antioxidant effects of these natural extracts and to establish a precise profile of their mode of action. In the study which has just been published, the antioxidant profile of the passion fruit (Passiflora edulis and Passiflora alata) has been established and demonstrated by techniques which make a distinction between the capacity of the extracts from passion fruit to neutralize the oxidizing species and their capacity to reduce the activity of the enzymes that produce these oxidizing species. Very common in Brazil, the passion fruit has shown itself to be an interesting source of antioxidants which are active on the oxidizing enzymes.

Crossing the intestinal barrier

As inflammatory reactions can rapidly become fatal, it is therefore necessary to reduce the formation of activated oxygen species by acting on the enzymes that produce them. The problem that researchers are often confronted by is the fact that the different molecules which have been identified for their antioxidant properties, polyphenols principally, must cross the intestinal barrier in order to become active. In other words, it is not enough to give an antioxidant in order to have quickly an efficient effect. Part of the active ingredient is eliminated and does not cross the intestinal barrier. This is why fundamental research is essential in order to determine the best way of increasing the efficiency of the active ingredient. Similarly, it is not enough to eat passion fruits, even in great quantities, in order to benefit from its antioxidant properties. Firstly, because the active ingredient is not concentrated as it would be in a medicine and secondly, because the greatest part of the antioxidants is not absorbed by the organism. Likewise, it seems more and more likely that dietary supplements containing antioxidants, sold under the label of “neutraceutical food” are not as efficient as hoped for or expected. 


Thierry Franck, researcher at CORD and co-author of this study points out: “Nevertheless, it is beneficial to eat fruit and vegetables. It is micro doses that are absorbed and which have positive effects on health. Regular consumption of fruits which have antioxidant properties clearly has a protective effect, but it is not sufficient when the individual is confronted by an uncontrolled inflammatory reaction”. Among the fruits which are of interest due to their antioxidant properties, the researchers have studied the pulp of passion fruit (Passiflora edulis and Passiflora alata) as well as the peel of Passiflora  edulis.

Passion fruit: a source of antioxidants

The antioxidant activity of extracts from the pulp and skin of the passion fruit has been studied on the oxidant activity of neutrophils and myeloperoxidase (MPO) of neutrophils (defense enzyme producing powerful oxidants), two elements that play a key role in inflammation. The effects of extracts from the passion fruit on the production of oxidizing species by the stimulated neutrophils have been assessed by a method of  chemiluminescence (CL) and their effects on the activities of the purified myeloperoxidase were measured by the SIEFED method (Specific Immunological Extraction Followed by Enzymatic Detection). The extracts of peel from Passiflora edulis show the strongest antioxidant properties from the measures carried out, thus opening the way for future uses as a source of natural flavonoids (polyphenols).

(1) Evaluation of the antioxydant activity of passion fruit (Passiflora edulis and Passiflora alata) extracts on stimulated neutrophils and myeloperoxidase activity assays. Maria Luiza Zeraik, Didier Serteyn, Ginette Deby-Dupont, Jean-Noël Wauters, Monique Tits, Janete H. Yariwake, Luc Angenot, Thierry Franck. Food Chemistry, Elsevier, 2011.