Antioxidants are essential in the body’s fight against the assault of free radicals and consequent ageing. Julien Demaude discusses the latest research into antioxidant formulations for longevity and anti-ageing, with a focus on resveratrol’s effect on oxidative damage
The antioxidant market is expanding, particularly in the US, so we’re constantly looking into the development of new antioxidant formulations and their effect on the skin. Certain actives do need more research, because we still don’t know their full capability as anti-ageing solutions.
Resveratrol is a well-known antioxidant and we have plenty of natural sources; around 70 plant species, nuts, nut weed and grapes. When we talk about resveratrol, and the communication between resveratrol and resveratrol derivatives, the effect could be very different.
The chemical structure of resveratrol is pretty simple. It’s a polyphenol and we can have a cis-resveratrol and a trans-resveratrol. In 1997, a prominent paper from Dr Chang reported that the topical application of resveratrol could reduce skin tumours by 98% in mice, and since then there have been many studies across the world, most notably on ageing and longevity.
Using resveratrol, scientists reported that they were able to increase the lifespan of yeast, followed by worms and fruit flies, and then fish. In 2012, scientists from Barcelona determined that resveratrol extended the lifespan in mice and honeybees. Resveratrol has interesting activity in different fields of medicine—neurological, cardiovascular, diabetes, chemotherapy, inflammation and cosmetic medicine.
In 1956, Dr Harman published an article in the Journal of Gerontology entitled, “Ageing: a theory based on free radical and radiation chemistry.” The paper concluded that cellular accumulation of free radical damage by use of biological components, leading to the degradation of body tissues, is the primary cause of cholinergic ageing. It was the first publication to make the link between resveratrol and its beneficial effect on ageing.
When we talk about ageing, we are talking about oxidative damage. We have two sources of reactive oxidative species (ROS). We have extrinsic sources—resveratrol stimulation generating external ROS—and we have an intrinsic sources; produced naturally during synthesis respiration and inflammation.
When we consider an antioxidant strategy, we need to think about multiple strategies. One requires exogenous antioxidants, requiring external supplementation, such as our current cosmeceutical products containing resveratrol, baicalin or vitamin E.
The other strategy needs to use endogenous antioxidants, such as those produced in normal serum metabolism to fight ROS production. Enzymes like glutathione, peroxidase, catalase, bedrobinol and antioxidant combinations have greater potential to neutralise the range of ROS emitted along the oxidation pathway.
Dr Harman also published a publication in the 1970s on his free radical theory of ageing, incorporating the role of mitochondrial ROS production in the ageing process.
Mitochondria is one of the primary internal sources of ROS, which are produced when oxygen acts as a final electron acceptor. Dr Harman stated that an accumulation of mitochondrial DNA mutation, caused by ROS production, is the principal determinator of the rate of human ageing.
We can therefore have a vicious cycle of radical damage. We have two sources of ROS production, from environmental stimulation and from internal production, which results in mitochondrial oxidative stress. We then have an increase of mitochondrial DNA mutation, followed by an increase of mitochondrial ROS production and again, a double increase of mitochondrial DNA mutation—it’s a vicious cycle which is very bad for the mitochondria and, therefore, for the cells.
There are plenty of diseases linked to mitochondrial dysfunction. We have neurodegenerative disease, diabetes mellitus and the premature ageing syndrome called lyceum cell syndrome. So mitochondria are key in terms of ROS production. In terms of skin, an inhibition in the mitochondrial oxidative stress level has a detrimental effect on the physiology of skin ageing.
We performed an interesting experiment, injecting mitochondria from older fibroblasts into younger fibroblasts—the combination caused rapid ageing, highlighting the effect of mitochondria into skin cells.
Returning to resveratrol, the active has a classical antioxidant effect, going through a scavenging activity against reactive oxygen species. The antioxidant can reduce mitochondrial ROS production, but it can also promote mitochondrial biogenesis. We also now know that it is able to stimulate a specific pathway; the NRF-2 pathway.
The NRF-2 pathway is the cellular antioxidant defence system, and is actually a small transcription factor—it’s very important to stimulate your own defence system. Resveratrol is able to boost the NRF-2 pathway and through this activation, the resveratrol can split the complex NRF-2 and keep one into the cytoplasm.
The NRF-2 transcription factor then goes into the nucleus, increasing the expression of antioxidant genes stimulating the production of over 200 enzymes dedicated to antioxidation. All of these enzymes and endogenous antioxidants are then able to link the ROS produced by cells. So it’s important to find a new strategy with antioxidants which can stimulate this pathway and quench the ROS pollution stimulated by environmental factors.
So what about the skin? A few years ago, collaborative research between McGill University in Montreal and L’Oreal showed that resveratrol is able to bind the keratin sides on cells. Resveratrol protects the keratin side by acting on mitochondria. Resveratrol takes on the properties of intra-cellular affectors protecting against age-related skin cell damage.
In another publication in 2013, we showed that in the specific reconstructed AB Skin Model, we were able to stimulate the NRF-2 pathway with resveratrol and increase the production of the glutacyan, one of the most powerful endogenous antioxidants that we have in our skin.
There are three main limitations with resveratrol. The first is the photo-instability of the active—if you were to put a resveratrol solution close to the window, you would see a change of the colour. That’s a big limitation for us in terms of formulation.
Then the second is its bioability. We know that resveratrol is rapidly metabolised after oral administration, decreasing the plasma concentration and the bioability. Topical administration seems the best way to overcome the inability of the active to maintain a good concentration.
The last limitation of resveratrol is its solubility. It has poor aqua solubility, and we are currently working on this limitation with new technology called hydrotropes. This technology is originally from the pharmaceutical field. We use hydrophilic actives, such as vitamin B3 and caffeine, and linking them to the resveratrol which is hydrophobic. This solution will enable the resveratrol to penetrate into the skin with the hydrophilic ingredients.
We carried out some interesting research with this combination, putting the formula at 45 degrees Celsius for two months. Results showed we were able to maintain a good concentration of resveratrol using the hydrotrope technology. Following a clinical evaluation with resveratrol hydrotropes, we now have a product containing baicalin and vitamin A. It’s better to have a cocktail than using just one antioxidant.
They study involved a critical evaluation on 55 subjects and evaluated different parameters like radiance, firmness, elasticity, density and smoothness. We saw improvements in firmness, elasticity and density after 12 weeks, which were better than with a resveratrol-only formula. Following ultrasound, we could see that compared to baseline after 12 weeks, the combined formula was able to increase skin density by almost 19 %.
We then went through different kinds of ageing bio-markers and we showed we could increase the quantity and the concentration of collagen three into the dermis. VEGF is a marker of intracellular information of oxidic stress and we were able to decrease the quantity of VEGF in our samples, thereby decreasing the inflammation process.
Dr Julien Demaude is the director of International Predictive Models for Evaluation at L’Oreal