Ascorbic acid 2-glucoside: An ascorbic acid pro-drug with longer-term antioxidant efficacy in skin

Top weapons in skin aging and actives to target the consequences of skin cell senescence

Skin aging has long been considered a purely cosmetic problem. However, as life expectancy increases, skin aging is taking on a functional dimension that goes beyond cosmetics and appearance. Preventive or therapeutic strategies are needed to target cellular senescence, a key process underlying the alterations in skin function and appearance that occur with aging, as well as to address the age-related skin changes associated with 'dermatoporosis' and chronic skin insufficiency/fragility syndrome. Thus, given the need for effective anti-aging products that improve both the appearance and function of the skin, it is essential to distinguish active ingredients that have been proven to be effective, among the large number of available over-the-counter cosmeceuticals. This brief review focuses on a core group of topical actives, describing their clinical effects on senescence and aging, and their molecular mechanisms of action. These actives include hyaluronic acid, which has hydrating and viscoelastic properties and has been shown to reduce skin atrophy; retinaldehyde, which activates retinoid receptors and increases cutaneous elasticity; vitamins C and E, which provide stable oxidative protection; and niacinamide, which reduces inflammation and mitigates the effects of senescence.

Modulation of copper sites in porphyrin metal-organic frameworks for electrochemical ascorbic acid sensing

Two metal-organic frameworks (MOFs) with different Cu-centered coordination structures were synthesized. By introducing 4,4-bipyridine as a linker in the Cu-MOFs, we have discovered that Cu-O, instead of Cu-N, is the active site with higher electrocatalytical activity towards ascorbic acid, which is essential to understand and develop Cu-based ascorbic acid sensors.

Transdermal Sustained Release Properties and Anti-Photoaging Efficacy of Liposome-Thermosensitive Hydrogel System

Drug delivery systems have become a research priority in the biomedical field. The incorporation of liposomes to hydrogels further forms more robust multifunctional systems for more effective and sustained topical drug delivery. In this study, carboxymethyl-modified chitosan/hyaluronic acid (CMC/HA, CMH) thermosensitive hydrogel is developed for sustained transdermal delivery of liposomes. Hydrogels are crosslinked by hydrogen bonding, hydrophobic interaction and electrostatic interaction. The gel properties can be regulated by substitution degree (DS), and when DS = 18.20 ± 0.67% (CMH2), the gel temperature is 37.8 °C, allowing rapid gelation at body temperature (315 s). Moreover, CMH2 hydrogel has suitable spreadability (17.7-57.2 cm2 ), viscosity (2133.4 mPa s) and porous structure, which facilitated its adhesion and application on the skin and liposomes delivery. The hydrogel can retard the liposomes release, and the release rate of ascorbyl glucoside (AA2G) is 33.92-49.35% in 24 h. Hydrogel avoids the rapid clearance of liposomes from the skin and improved the skin retention, achieving the long-term release of bioactive components. Liposome-hydrogel system more efficiently promotes the anti-photoaging effect of AA2G on skin, reducing epidermal thickness, melanin deposition and lipid oxidative damage and increasing collagen density. Therefore, liposome-hydrogel systems are proposed as multifunctional delivery systems for sustained transdermal delivery.

Comparative Studies on the Photoreactivity, Efficacy, and Safety of Depigmenting Agents

Depigmenting products are increasingly used to counteract skin hyperpigmentation and related psychosocial issues. This study aimed to compare different depigmenting agents-4-butylresorcinol; bakuchiol; tranexamic acid; ascorbyl glucoside; α-arbutin; and ascorbic acid-for photoreactivity; tyrosinase inhibition; and safety. Photoreactivity was assessed using the Reactive Oxygen Species assay. In vitro tyrosinase inhibition was compared, and cell viability was assessed in B-16V melanocytes to evaluate safety. Results showed 4-butylresorcinol, ascorbyl glucoside, and α-arbutin are non-photoreactive, while for ascorbic acid and bakuchiol it was not possible to reach conclusive results due to the lack of specificity of the ROS assay. 4-Butylresorcinol, acting as a competitive inhibitor, displayed potent tyrosinase inhibition, followed by ascorbic acid and bakuchiol. Both 4-butylresorcinol and bakuchiol reduced cell viability in a concentration-dependent manner. The insights obtained in this work support the development of depigmenting products by providing useful scientific guidance on the photostability, tyrosinase inhibitory efficacy, and skin safety of depigmenting agents.

Development of Emulsions Containing L-Ascorbic Acid and α-Tocopherol Based on the Polysaccharide FucoPol: Stability Evaluation and Rheological and Texture Assessment

The main function of vitamin C, as an antioxidant, is to combat free radicals and prevent premature aging, smoothing wrinkles and expression lines. In addition, it acts directly on depigmentation and prevention of blemishes on the skin. In this study, natural oils (30 wt.%) and α-tocopherol (2.5 wt.%) containing oil-in-water (O/W) emulsions stabilized with the bacterial fucose-rich polysaccharide FucoPol were formulated, adding L-ascorbic acid as an antioxidant. The optimized formulations were obtained with 8.0 wt.% L-ascorbic acid for the Olea europaea oil formulation (C1) with a ƞ value of 2.71 Pa.s (measured at shear rate of 2.3 s−1) and E24 = 96% and with 15 wt.% L-ascorbic acid for the Prunus amygdalus dulcis formulation (C2) with a ƞ value of 5.15 Pa.s (at a shear rate of 2.3 s−1) and E24 = 99%. The stability of the FucoPol-based formulations was investigated over 45 days at 4 °C, 20 °C, and 30 °C. The results showed that all formulations maintained the organoleptic characteristics, with pH variations (5.7–6.8 for C1, and 5.5–6.03 for C2) within the regulations for cosmetic products (4 ≤ pH ≤ 7). The accelerated stability tests proved the formulations’ stability at 4 °C with EI = 95% for C1 and EI = 100% for C2. The rheological assessment demonstrated that the formulation presents a shear-thinning and liquid-like behavior. Regarding textural parameters, formulations C1 and C2 displayed an increase in firmness and consistency with similar spreadability during the shelf life. These findings further demonstrate FucoPol’s functional properties, acting as an emulsifier and stabilizer polysaccharide in cosmetic formulations containing L-ascorbic acid.

Antioxidants in Sunscreens: Which and What For?

Ultraviolet (UV) radiation promotes the generation of reactive oxygen species (ROS) and nitrogen species (RNS), resulting in skin damage. Cosmetic industries have adopted a strategy to incorporate antioxidants in sunscreen formulations to prevent or minimize UV-induced oxidative damage, boost photoprotection effectiveness, and mitigate skin photoaging. Many antioxidants are naturally derived, mainly from terrestrial plants; however, marine organisms have been increasingly explored as a source of new potent antioxidant molecules. This work aims to characterize the frequency of the use of antioxidants in commercial sunscreens. Photoprotective formulations currently marketed in parapharmacies and pharmacies were analyzed with respect to the composition described on the label. As a result, pure compounds with antioxidant activity were found. The majority of sunscreen formulations contained antioxidants, with vitamin E and its derivatives the most frequent. A more thorough analysis of these antioxidants is also provided, unveiling the top antioxidant ingredients found in sunscreens. A critical appraisal of the scientific evidence regarding their effectiveness is also performed. In conclusion, this work provides an up-to-date overview of the use of antioxidants in commercial sunscreens for a better understanding of the advantages associated with their use in photoprotective formulations.

Ascorbic Acid (Vitamin C) as a Cosmeceutical to Increase Dermal Collagen for Skin Antiaging Purposes: Emerging Combination Therapies

Ascorbic acid (AA) is an essential nutrient and has great potential as a cosmeceutical that protects the health and beauty of the skin. AA is expected to attenuate photoaging and the natural aging of the skin by reducing oxidative stress caused by external and internal factors and by promoting collagen gene expression and maturation. In this review, the biochemical basis of AA associated with collagen metabolism and clinical evidence of AA in increasing dermal collagen and inhibiting skin aging were discussed. In addition, we reviewed emerging strategies that have been developed to overcome the shortcomings of AA as a cosmeceutical and achieve maximum efficacy. Because extracellular matrix proteins, such as collagen, have unique amino acid compositions, their production in cells is influenced by the availability of specific amino acids. For example, glycine residues occupy 1/3 of amino acid residues in collagen protein, and the supply of glycine can be a limiting factor for collagen synthesis. Experiments showed that glycinamide was the most effective among the various amino acids and amidated amino acids in stimulating collagen production in human dermal fibroblasts. Thus, it is possible to synergistically improve collagen synthesis by combining AA analogs and amino acid analogs that act at different stages of the collagen production process. This combination therapy would be useful for skin antiaging that requires enhanced collagen production.

Efficient dermal delivery of ascorbic acid 2-glucoside with photoacoustic waves

OBJECTIVE

Ascorbic acid (i.e., vitamin C) is an important antioxidant present in skin. The protective role of vitamin C against photoaging motivated numerous attempts to promote its topical delivery, with a success limited by its chemical instability and poor skin permeability. Vitamin C precursors, such as ascorbic acid 2-glucoside (AA2G), that are metabolized to vitamin C by enzymes present in the skin, solve the problem of stability but are limited by low skin permeability. We developed a 2% (w/v) gel formulation of AA2G application (viscosity 4.30 × 10⁴ Pa.s, pH 5.94) and compared its passive dermal delivery with the delivery promoted by photoacoustic waves that transiently perturb the skin barrier.

METHODS

Photoacoustic (PA) waves were generated by laser pulses absorbed by piezophotonic (light-to-pressure) transducers. Pig skin samples were exposed to the 2% AA2G formulation alone or combined with 5 minutes of PA waves. One hour later, AA2G was extracted from the skin and quantified by reverse-phase HPLC. AA2G transdermal fluxes using Franz cells with 760 μm thick pig skin samples were also measured.

RESULTS

PA waves transiently enhanced skin permeability and increased dermal delivery of AA2G. AA2G was released from the formulation nearly quantitatively (92.6 ± 6.2%) in 24 hours, showing a non-Fickian behaviour controlled by diffusion and swelling. AA2G dermal delivery with exposure for 5 minutes to PA waves was compared with passive delivery to pig skin. PA waves increased the delivery of AA2G to the skin by a factor of 15 fold with respect to passive delivery, as measured from skin extracts after 1 hour of contact of the formulation with the skin.

CONCLUSION

5 minutes of exposure to PA waves is a safe and effective method to deliver large quantities of AA2G to the skin.