Resveratrol (often shorten as RSV) is a natural molecule produced by plants as a defence mechanism for external stressors, such as UV radiation, or against fungal and microbial invasion. The main sources of RSV are peanuts, blueberries, cranberries and especially red grapes, that are also part of the human diet (See Figure 1).
Figure 1. Resveratrol structure and main sources.
In addition to its protective activity in plants, this compound has a number of functions that are of great interest to humans, namely as an antioxidant, antiviral, cardioprotective, anti-inflammatory or antitumoral agent . Particularly, resveratrol is an interesting active ingredient in cosmetics not only for its ability to cross the skin barrier but also for preventing skin inflammation and the degradation of collagen, also known as anti-photoaging activity . The combination of these properties and the effects exerted makes them a promising candidate for anti-aging formulations.
So far so good. However, this compound has also some limitations:
Availability: even though the resveratrol is naturally synthesized by the plants, its extraction, separation and purification are expensive as well as polluting. Also, its availability is very conditioned by the presence of abiotic stress factors.
Stability: its use is limited due to the sensibility of UV radiation or high pH conditions that isomerize the molecule from the trans (active) form to the cis (inactive) form (See Figure 2).
Figure 2. Resveratrol isomerization process.
Then, should we give up on the molecule of resveratrol? Absolutely not. Although it presents some drawbacks regarding stability and sustainability, some alternative methods are being studied to overcome these barriers.
Initially, to increase the availability, chemical synthesis of resveratrol was performed but the larger amounts of undesirable by-products hindered the purification. However, the current production in several microbial hosts can be spotted as a different approach specially for industrial-scaled processes .
To increase the stability, the use of enzyme-catalysed esterification reactions to attach a suitable molecule (a carboxylic acid or an ester) and form the esterified derivative of resveratrol has become a strategy of great interest (See Figure 3). The difference relies on the reactivity of the hydroxyl (-OH) groups: once the esterification reaction is done, the hydroxyl reactivity decreases and consequently, the stability increases. The esterified derivatives also present more enhanced bioactive properties than the original molecule such as bioavailability and skin permeability, without losing antioxidant activity [4, 5]. The relevance of this strategy also relies on the fact that this reaction can be carried out in a sustainable way. By performing enzyme-catalysed reactions, higher yields are obtained, mild conditions are required and the undesirable by-products are drastically reduced. This results into a very beneficial approach since it improves the stability of the formulation and does not pollute the environment at the same time.
Figure 3. General reaction scheme of (A) esterification and (B) transesterification of resveratrol.
Further investigation must be conducted to confirm the efficacy of these compounds both in vivo and in vitro. However, resveratrol and its esterified derivatives constitute a promising alternative for the formulation of effective and sustainable anti-aging cosmetics.
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