In vitro Safety Assessment of Extracts and Compounds From Plants as Sunscreen Ingredients.

This work investigated the safety of extracts obtained from plants growing in Colombia, which have previously shown UV-filter/antigenotoxic properties. The compounds in plant extracts obtained by the supercritical fluid (CO2) extraction method were identified using gas chromatography coupled to mass spectrometry (GC/MS) analysis. Cytotoxicity measured as cytotoxic concentration 50% (CC50) and genotoxicity of the plant extracts and some compounds were studied in human fibroblasts using the trypan blue exclusion assay and the Comet assay, respectively. The extracts from Pipper eriopodon and Salvia aratocensis species and the compound trans-ß-caryophyllene were clearly cytotoxic to human fibroblasts. Conversely, Achyrocline satureioides, Chromolaena pellia, and Lippia origanoides extracts were relatively less cytotoxic with CC50 values of 173, 184, and 89 µg/mL, respectively. The C. pellia and L. origanoides extracts produced some degree of DNA breaks at cytotoxic concentrations. The cytotoxicity of the studied compounds was as follows, with lower CC50 values representing the most cytotoxic compounds: resveratrol (91 µM) > pinocembrin (144 µM) > quercetin (222 µM) > titanium dioxide (704 µM). Quercetin was unique among the compounds assayed in being genotoxic to human fibroblasts. Our work indicates that phytochemicals can be cytotoxic and genotoxic, demonstrating the need to establish safe concentrations of these extracts for their potential use in cosmetics.

A new eco-friendly and water-resistant sunscreen agent: Lecithin-based multilamellar liposomes.

BACKGROUND: UV skin exposure is an important matter of public health, as the worldwide rising prevalence of skin cancers indicates. However, a wide majority of commercially available sunscreens are responsible for ocean ecosystem damages such as coral reef degradation and phytoplankton mortality. AIMS: To answer the urge for new eco-friendly UV filters, we studied the use of lecithin-based multilamellar liposomes (MLLs) of controlled size and elasticity as a bio-sourced and biodegradable alternative to classic sunscreens. These parameters control allows different skin layers targeting. METHODS: The performance of two different MLLs compositions and a commercially available SPF50+ water-resistant liposomal sunscreen was compared on skin explants. SC-MLLs target the stratum corneum and Epi-MLLs the whole epidermis. Preparations were applied prior to skin irradiation. Their efficiencies were evaluated histologically (hematoxylin and eosin staining plus cyclobutane pyrimidine dimer [CPD] immunostaining) and by skin barrier quality assessment (trans-epithelial electrical resistance). Adhesiveness to the skin was also investigated. RESULTS: Altogether, ex vivo results indicate MLLs offer a solar protection as effective as a SPF50+ water-resistant liposomal sunscreen but with a better skin adhesiveness and an improved skin barrier function. CONCLUSION: Lecithin-based MLLs of controlled physicochemical parameters can be used as a new eco-friendly and water-resistant agent for solar protection. The stratum corneum targeted action of SC-MLLs appears to be more interesting, as SC-MLLs exhibit an overall better performance than Epi-MLLs at a lower cost. The skin barrier improvement showcased could be of interest to people suffering from dry skin or skin barrier impairment related disease.

Bioconjugation of Vegetable Oils with UV Absorbers: New Approach in Skin Photoprotection.

We reported the tunable synthesis of new vegetable oil-UV filter bioconjugates using sea buckthorn oil (SBO) and p-methoxycinnamic acid (p-MCA) as an alternative to the common UV filter, ethylhexyl-p-methoxycinnamate (octinoxate). The synthetic strategy is based on the sustainable ring-opening reaction of epoxidized SBO with p-MCA in heterogenous catalysis in eco-friendly solvents. The amount of UV-absorptive moieties grafted on the triglyceride backbone is controlled by different epoxidation degrees as determined by NMR spectroscopy. The performance of the new UV-absorber bioconjugates was assessed by in vitro sun protection factor (SPF) measurements after inclusion in SBO-ethylcellulose (EC) oleogels and comparison with the SPF value of the SBO-EC-octinoxate oleogel with equivalent p-MCA acid moieties (10% wt/wt). The concentration obtained for the SBO-EC oleogel formulated with the bioconjugate with the lowest degree of functionalization, namely 55%, represents 45% of the SPF determined for the SBO-EC-octinoxate oleogel, regardless of the concentration of measured solutions. The new concept of vegetable oil-UV-absorber bioconjugates has potential UV-B photoprotective properties when included in oleogel formulations and deserves further investigation of their properties and stability including association with UV-A absorbers, respectively.

Solid SiO2-Sealed Mesoporous Silica for Synergistically Combined Use of Inorganic and Organic Filters to Achieve Safe and Effective Skin Protection from All-Band UV Radiation.

To effectively shield the full band of ultraviolet (UV) radiation and provide desirable protection, the combination of inorganic and organic filters was often used to protect human skin from the serious harm of UV exposure. However, the incompatibility of different filters and their mutual negative effect limit the production of multifilter sunscreen. In addition, the hazard of reactive oxygen species (ROS) produced by inorganic filters after UV exposure and the skin permeability of organic filters remain unresolved problems. In this study, titanium dioxide (TiO2) and diethylamino hydroxybenzoyl hexyl benzoate (DHHB), two kinds of common filters with complementary UV shielding range, were first encapsulated into large mesoporous silica nanoparticles (MSN, ∼300 nm) to obtain MSN-TiO2 and MSN-DHHB. Also, a SiO2 coating was then made to seal and stabilize the MSN-TiO2 and MSN-DHHB. The structure, UV screen function, and safety of the SiO2-coated filters, MSN-TiO2@SiO2 and MSN-DHHB@SiO2, were evaluated. The good mechanical stability exhibited by the solid SiO2 layer prevented the release and skin penetration of the sealed DHHB and the photocatalysis of TiO2. Furthermore, the combination of MSN-TiO2@SiO2 and MSN-DHHB@SiO2 in sunscreen cream showed excellent UV shielding performance on covering the whole UV radiation range without mutual interference. Therefore, coating SiO2 over MSN is a feasible strategy for entrapping various filters to improve their photostability, preventing skin penetration and ROS generation, and enhancing their compatibility with different sunscreen formulations.

Natural products and extracts from plants as natural UV filters for sunscreens: A review.

Although solar exposure is necessary for human health, phototoxicology induced by excessive UVB and UVA radiation, which involves sunburns, skin aging and even tumorigenesis, has been widely researched. Sunscreen is one of the most important ways to protect skin from UV phototoxic damage. As well as inorganic and organic UV filters, some natural products or plant extracts with aromatic rings in their structures, such as flavonoids or polyphenols, can absorb UV to reduce sunburn, acting as a natural UV filter; they also show antioxidant or/and anti-inflammatory activity. This could explain why, although there are no officially approval natural commercial sun-filters, more and more commercial sunscreen products containing plant extracts are available on the market. Here we summarize articles focusing on natural UV filters from plant published in the last 6 years, selecting the most significant data in order to better understand the photoprotective activity of natural products and extracts from plants, including their major constituents and main biological effects, methods for evaluating UV radiation resistance, anti-UV radiation experimental models and anti-UV radiation mechanisms.

Chemical and mechanical accelerated and long-term stability evaluation of sunscreen formulation containing grape seed extract.

BACKGROUND: Sunscreens and catechins from grape seed extract (GSE) are sensitive to various environmental factors and undergo certain changes over time that might affect the effectiveness of the final product. To this date, effects of thermal storage conditions have not been sufficiently addressed to guarantee the long-term stability of sunscreen formulations. AIMS: To study the chemical and mechanical accelerated and long-term stability of sunscreen formulation containing GSE at the Climatic Zone IVb conditions. METHODS: Stability studies were performed for 6 months for accelerated stability study at 30°C ± 2 and 50°C ± 2, 75 ± 5% relative humidity; and long-term stability study at 5°C ± 5. The quantification of constituents of three formulations: sunscreen with GSE, cream with UV filters only, and cream with GSE only was performed by high-performance liquid chromatography. In vitro spectrophotometry was used to determine changes in sun protection effectiveness through SPF and UVAPF values. Mechanical stability was evaluated by textural and rheological analyzes. RESULTS: All tested formulations were less stable at high-temperature conditions. The contents of catechin (С) and epicatechin (EC) in sunscreen with GSE were reduced to 37% and 50% at 50°C, respectively, whereas UV filters appeared to be stable. However, despite the significant reduction in catechins over time, polyphenols in GSE remained unchanged at different stored conditions. The SPF values and water resistance of sunscreen with GSE were maintained throughout the study. CONCLUSIONS: A current in vitro study has shown that sunscreen with GSE is a value-added anti-aging ingredient in sunscreen formulation because its polyphenolic composition as well as SPF values and water resistance were maintained under all temperature conditions over time.

Influence of TiO2 nanocomposite UV filter surface chemistry and their interactions with organic UV filters on uptake and toxicity toward cultured fish gill cells.

Aquatic environments have been found to be contaminated with a variety of inorganic and organic UV filters. This includes novel nano-sized titanium dioxide (TiO2) composite particles, which have been increasingly developed and incorporated into commercial sunscreens in recent years. So far, relatively little is known about the effects of this novel class of UV filters on aquatic life. Therefore, this study aimed to determine and compare the toxicity of three such nanoparticulate TiO2 UV filters with different surface coatings, namely Eusolex® T-Avo (SiO2-coated), T-Lite™ SF (Al(OH)3/PDMS-coated), and Eusolex® T-S (Al2O3/stearic acid-coated) either alone, or in the presence of selected organic UV filters (octinoxate, avobenzone, octocrylene), toward fish using RTgill-W1 cell cultures as an in vitro experimental model. Besides standard exposure protocols, alternative approaches (i.e., exposure to water accommodated fractions (WAFs), hanging-drop exposure) were explored to account for nanoparticle (NP)-specific fate in the medium and obtain additional/complementary information on their toxicity in different conditions. The AlamarBlue, CFDA-AM and Neutral Red Retention (NR) assays were used to measure effects on different cellular endpoints. Transmission electron microscopy (TEM) was used to examine NP uptake. Our results showed that none of the TiO2 NP UV filters were cytotoxic at the concentrations tested (0.1-10 µg/mL; 24 h) but there were differences in their uptake by the cells. Thus, only the hydrophilic T-AVO was detected inside cells, but the hydrophobic T-Lite SF and T-S were not. In addition, our results show that the presence of NPs (or the used dispersant) tended to decrease organic UV filter toxicity. The level of combination effect depended on both NP-type (surface chemistry) and concentration, suggesting that the reduced toxicity resulted from reduced availability of the organic UV filters due to their adsorption to the NP surface. Thus, mixtures of TiO2 NP UV filters and organic UV filters may have a different toxicological profile compared to the single substances, but probably do not pose an increased hazard.

Selected Extracts from High Mountain Plants as Potential Sunscreens with Antioxidant Capacity.

The photoprotective and antioxidant activities of extracts of six species of plants collected in a high mountain ecosystem at 3150 m.a.s.l. were evaluated. In vitro photoprotection according to UVA-UVB absorption spectrum, Sun Protection Factor (SPF), UVA Protection Factor (UVAPF), (critical wavelength) λc and UVA/UVB Ratio were assessed. Also, the antioxidant activity was determined using the DPPH radical assay and the inhibition of lipid peroxidation in methyl linoleate (MeLo). Total anthocyanins content (TAC) and total polyphenolic content (TPC) were evaluated. Among the extracts evaluated, the extract of B. antioquensis, an endemic plant of Colombia, showed a significant photoprotection against UVA-UVB range, with SPF values of 15 ± 2 and UVAPF of 7 ± 1, λc : 378, UVA/UVB Ratio: 0.78. Furthermore, this extract presented an excellent antioxidant activity, with EC50 of 0.17 ± 0.04 g of dry extract/mmol DPPH, a value of TPC of 464 ± 9 mg gallic acid equivalents (GAE)/g dry extract and significant inhibition of MeLo peroxidation. The results suggest that the extract of B. antioquensis has the best quality to be a source of new UV filters, with a broad spectrum of protection and antioxidant properties.

Unravelling the Photoprotection Properties of Garden Cress Sprout Extract.

Plants, as with humans, require photoprotection against the potentially damaging effects of overexposure to ultraviolet (UV) radiation. Previously, sinapoyl malate (SM) was identified as the photoprotective agent in thale cress. Here, we seek to identify the photoprotective agent in a similar plant, garden cress, which is currently used in the skincare product Detoxophane nc. To achieve this, we explore the photodynamics of both the garden cress sprout extract and Detoxophane nc with femtosecond transient electronic absorption spectroscopy. With the assistance of liquid chromatography-mass spectrometry, we determine that the main UV-absorbing compound in garden cress sprout extract is SM. Importantly, our studies reveal that the photoprotection properties of the SM in the garden cress sprout extract present in Detoxophane nc are not compromised by the formulation environment. The result suggests that Detoxophane nc containing the garden cress sprout extract may offer additional photoprotection to the end user in the form of a UV filter booster.

Assessment of Natural Sunlight Protection Provided by 10 High-SPF Broad-Spectrum Sunscreens and Sun-Protective Fabrics.

In 1978, the FDA Advisory Panel proposed both indoor and natural sunlight SPF testing methods but reverted to indoor testing only in 1993. Today's sunscreen sun protection and broad-spectrum claims are based on mandated clinical tests using solar simulators and in vitro spectrophotometers. This research evaluated the protection of 10 high-SPF (30-110), broad-spectrum sunscreen products, as well as 6 sun-protective fabrics against natural sunlight in Arequipa, Peru. Each of the 17 subjects was exposed to natural sunlight for 1 h and 59 min under clear skies, with temperatures and humidity similar to those in an indoor clinical laboratory. Test sites were photographed 16-24 h later. Four dermatologists evaluated the photographs for erythema and persistent pigment darkening (PPD). Perceptible sun-induced skin injury (sunburn and/or pigmentation) was detected at 97% of the sunscreen-protected scores. The most sun-sensitive subjects obtained the least erythema protection. The higher the SPF was, the higher the erythema protection, but the intensity of PPD was also higher. The 2 sunscreens using only FDA-approved sunscreen filters rated 30 SPF and 45+ SPF performed poorly: Eighty-one percent of the 136 scores were graded 1 minimal erythema dose or higher erythema, achieving, at a maximum, SPF of 5-7 in natural sunlight. Sun-protective fabrics tested provided excellent sun protection. The erythema and PPD observed through the sunscreens in less than 2 h are incongruous with the broad-spectrum, high-SPF sunscreen claims. Reapplying these sunscreens and staying in the sun longer, as stated on the product labels, would have subjected the subjects to even more UV exposure. High-SPF, broad-spectrum sunscreen claims based on indoor solar simulator testing do not agree with the natural sunlight protection test results.

The potential effect of Polypodium leucotomos extract on ultraviolet- and visible light-induced photoaging.

Photoaging induced by both ultraviolet and visible light has been shown to lead to increased inflammation and dysregulation of the extracellular matrix. Standardized extract of the Polypodium leucotomos fern, PLE, possesses anti-inflammatory and antioxidant properties, and has been shown to potentially mitigate photoaging through various mechanisms. This comprehensive review presents the data available on the effects of P. leucotomos extract on UV and VL-induced photoaging in vitro as well as in vivo in murine and human models.

From Sea to Skin: Is There a Future for Natural Photoprotectants?

In the last few decades, the thinning of the ozone layer due to increased atmospheric pollution has exacerbated the negative effects of excessive exposure to solar ultraviolet radiation (UVR), and skin cancer has become a major public health concern. In order to prevent skin damage, public health advice mainly focuses on the use of sunscreens, along with wearing protective clothing and avoiding sun exposure during peak hours. Sunscreens present on the market are topical formulations that contain a number of different synthetic, organic, and inorganic UVR filters with different absorbance profiles, which, when combined, provide broad UVR spectrum protection. However, increased evidence suggests that some of these compounds cause subtle damage to marine ecosystems. One alternative may be the use of natural products that are produced in a wide range of marine species and are mainly thought to act as a defense against UVR-mediated damage. However, their potential for human photoprotection is largely under-investigated. In this review, attention has been placed on the molecular strategies adopted by marine organisms to counteract UVR-induced negative effects and we provide a broad portrayal of the recent literature concerning marine-derived natural products having potential as natural sunscreens/photoprotectants for human skin. Their chemical structure, UVR absorption properties, and their pleiotropic role as bioactive molecules are discussed. Most studies strongly suggest that these natural products could be promising for use in biocompatible sunscreens and may represent an alternative eco-friendly approach to protect humans against UV-induced skin damage.

Protection against UVB deleterious skin effects in a mouse model: effect of a topical emulsion containing Cordia verbenacea extract.

Cordia verbenacea DC (Boraginaceae) is a flowering shrub found along the Brazilian Atlantic Forest, Brazilian coast, and low areas of the Amazon. The crude extract of its leaves is widely used in Brazilian folk medicine as an anti-inflammatory, both topically and orally. The aim of this study is to evaluate the activity of C. verbenacea ethanolic leaves extract (CVE) against UVB-triggered cutaneous inflammation and oxidative damage in hairless mice. CVE treatment recovered cutaneous antioxidant capacity demonstrated by scavenging ABTS+ free radical and iron-reducing antioxidant potential evaluated by FRAP. CVE also controlled the following UV-triggered events in the skin: reduced glutathione (GSH) depletion, catalase activity decrease, and superoxide anion (O⋅-) build-up. Furthermore, mice treated with CVE exhibited less inflammation, shown by the reduction in COX-2 expression, TNF-α, IL-1ß, IL-6, edema, and neutrophil infiltration. CVE also regulated epidermal thickening and sunburn cells, reduced dermal mast cells, and preserved collagen integrity. The best results were obtained using 5% CVE-added emulsion. The present data demonstrate that topical administration of CVE presents photochemoprotective activity in a mouse model of UVB inflammation and oxidative stress. Because of the intricate network linking inflammation, oxidative stress, and skin cancer, these results also indicate the importance of further studies elucidating a possible role of C. verbenacea in the prevention of UVB-induced skin cancer and evaluating a potential synergy between CVE and sunscreens in topical products against UVB damaging effects to the skin.

Chemical Composition and Ultraviolet Absorption Activity of an Aqueous Alkali Extract from the Fruiting Bodies of the Tinder Conk Mushroom, Fomes fomentarius (Agaricomycetes).

White rot mushroom Fomes fomentarius is a medicinal fungus with great potential to be explored. This work focused on the chemical composition of a basic aqueous extract from F. fomentarius fruiting bodies. The extract was mostly composed of phenolics, carbohydrates, minerals, and crude fat with a low amount of proteins and chitin. One-third of the total carbohydrates were in the form of beta-glucans with minor amounts of alpha-glucans. The most valuable essential part of the extract was composed of an acid-resistant ultraviolet (UV)-absorbing mixture of phenolic compounds such as melanins, lignins, and humic acids. These compounds, also referred to as melanin-like pigments, provided for the high antioxidant activity of the extract measured in vitro. Moderate sun-protective capacity was observed with regard to UVB rays and also expected in the UVA range. Quantification of melanin-like pigments in the F. fomentarius extract was possible either gravimetrically as acid-insoluble residue or spectrophotometrically in the UV region. Melanin estimation, based on nitrogen measurements, offered misleading results due to the presence of nitrogen-free melanins along with other nitrogen-containing compounds such as proteins and chitin. F. fomentarius water-soluble basic extract, containing beta-glucans and rich in melanin-like substances, could be used, for example, for topical skin application to prevent cell damage caused by excessive UV exposure or cytotoxic free radicals. The bioactive potential, safety, and further applications of the F. fomentarius extract are currently being investigated.

The real UVB photoprotective efficacy of vegetable oils: in vitro and in vivo studies.

Some vegetable oils are currently being promoted as a safe alternative to commercial sunscreens. The true UVB photoprotective efficacy of 14 virgin vegetable oils and the suitability of the dilution method for determining their SPF value were evaluated. Oils and standard sunscreens were investigated in vitro by the Mansur's method in Slovakia and in vivo by the ISO method in the Czech Republic. SPF values in vitro (0.1; 0.0; 0.4; 0.2 and 0.2) and in vivo (2.5; 1.2; 2.6; 2.6; and 2.8) of the five most promoted oils (from carrot seed, coconut, raspberry seed, rosehip seed, and wheat germ) were significantly lower than the values reported in the controversial studies. We have shown that the overestimated SPF values of these oils were determined by authors who did not strictly follow Mansur's original methodology. The other eight vegetable oils also provide no or negligible SPF values. Only the in vitro SPF value of 11.2 tamanu oil is worth mentioning, probably due to high proportion of calophyllolides. In vitro and in vivo SPF ratios from 1.14 to 0.94 obtained by two methods in two laboratories for six commercial sunscreen oils used as controls confirm the correctness of performing the Mansur's method in this study. However, this dilution method has proven to be fundamentally flawed in determining the SPF value of substances with such negligible photoprotection as most vegetable oils can provide. An SPF value of less than 1, which can be determined by this Mansur's method, is physiologically impossible and meaningless.

Characterization of a lignin from Crataeva tapia leaves and potential applications in medicinal and cosmetic formulations.

Lignins are phenolic macromolecules that have several applications. In this work, we examine some biological activities of a lignin-like macromolecule isolated from the Crataeva tapia leaves, not yet studied to evaluate its potential applications in medicinal and cosmetic formulations. Lignin was obtained by alkaline delignification and its physical-chemical characterization was made by means of FT-IR, UV-Vis, NMR spectroscopy, elementary analysis, molecular mass determination and thermal analysis. Lignin is of the GSH type, with levels of hydrogen (5.10%), oxygen (27.18%), carbon (67.60%), nitrogen (0.12%) and phenolic content of 189.6 ± 9.6 mg GAE/g. In addition, it is a thermally stable macromolecule with low antioxidant activity. Cytotoxicity and cytokine production were assessed by flow cytometry. The photoprotective activity was evaluated by adding different concentrations of lignin to a commercial cream. Lignin was not cytotoxic, it stimulated the production of TNF-α, IL-6 and IL-10 and did not promote a significant change in nitric oxide levels. In addition, this macromolecule was able to promote increased absorption of ultraviolet light from a commercial cream. These results reinforce the ethnopharmacological use of C. tapia leaves and suggest the need for further studies to determine the potential medicinal and cosmetic applications (sunscreen) of lignin from C. tapia leaves.

Preparation of pH-sensitive food packaging film based on konjac glucomannan and hydroxypropyl methyl cellulose incorporated with mulberry extract.

A pH-sensitive food packaging film was prepared based on konjac glucomannan (KGM) and hydroxypropyl methyl cellulose (HPMC) incorporated with mulberry extracts2 (MBE). FT-IR and XRD analysis revealed that there are good molecular interactions among the three components. The incorporation of MBE into KGM and HPMC (KH) films can significantly improve the mechanical properties and UV resistance. Notably, the KH-MBE-20% film almost completely blocked UV light in the range of 200-600 nm. The best antioxidant and antibacterial properties were obtained when the addition of MBE in the composite film was 20%. In addition, KH-MBE film has good responsiveness to buffers with pH range from 2 to 12. In visual monitoring experiments using the film on fresh fish, the color of the KH-MBE film changed from purple to gray to yellow as the freshness of the fish decreased, and the KH-MBE-20% film had the best color stability. Therefore, intelligent packaging of KH-MBE film has potential applications in real-time monitoring of fish freshness.

Sunscreens in the United States: Current Status and Future Outlook.

Incidence rates of nonmelanoma skin cancer and melanoma have been on the rise in the USA for the past 25 years. UV radiation (UVR) exposure remains the most preventable environmental risk factor for these cancers. Aside from sun avoidance, sunscreens continue to provide the best alternative protection. UVR directly damages DNA and causes indirect cellular damage through the creation of reactive oxygen species, the sum of which leads to cutaneous immunosuppression and a tumorigenic milieu. The current generation of sunscreens protect from UVR through two main mechanisms: absorption and deflection. In the USA, the Food and Drug Association (FDA) regulates sunscreen products which are considered over-the-counter drugs. With the release of new FDA testing and labeling requirements in 2011 and the enactment of the Sunscreen Innovation Act in 2014, sunscreen manufacturers are now required to evaluate their products not only on the sun protection factor (SPF) but also on broad-spectrum UVA protection. The American Academy of Dermatology Association and the American Academy of Pediatrics have provided specific recommendations for proper sun protection and sunscreen usage with the continual goal of increasing public awareness and compliance with appropriate sun protective measures. Antioxidants, photolyases, and plant polyphenols remain an interesting avenue of research as additives to sunscreens or stand-alone topical or oral products that appear to modulate the immunosuppressive effects of UVR on the skin. Additionally, although UVR induces endogenous cutaneous production of vitamin D, its damaging effects overshadow this positive benefit, especially in light of the ease of achieving recommended amounts of vitamin D through diet and supplementation.

Efficacy, Stability, and Safety Evaluation of New Polyphenolic Xanthones Towards Identification of Bioactive Compounds to Fight Skin Photoaging.

Antioxidants have long been used in the cosmetic industry to prevent skin photoaging, which is mediated by oxidative stress, making the search for new antioxidant compounds highly desirable in this field. Naturally occurring xanthones are polyphenolic compounds that can be found in microorganisms, fungi, lichens, and some higher plants. This class of polyphenols has a privileged scaffold that grants them several biological activities. We have previously identified simple oxygenated xanthones as promising antioxidants and disclosed as hit, 1,2-dihydroxyxanthone (1). Herein, we synthesized and studied the potential of xanthones with different polyoxygenated patterns as skin antiphotoaging ingredients. In the DPPH antioxidant assay, two newly synthesized derivatives showed IC50 values in the same range as ascorbic acid. The synthesized xanthones were discovered to be excellent tyrosinase inhibitors and weak to moderate collagenase and elastase inhibitors but no activity was revealed against hyaluronidase. Their metal-chelating effect (FeCl3 and CuCl2) as well as their stability at different pH values were characterized to understand their potential to be used as future cosmetic active agents. Among the synthesized polyoxygenated xanthones, 1,2-dihydroxyxanthone (1) was reinforced as the most promising, exhibiting a dual ability to protect the skin against UV damage by combining antioxidant/metal-chelating properties with UV-filter capacity and revealed to be more stable in the pH range that is close to the pH of the skin. Lastly, the phototoxicity of 1,2-dihydroxyxanthone (1) was evaluated in a human keratinocyte cell line and no phototoxicity was observed in the concentration range tested.

From sunscreens to medicines: Can a dissipation hypothesis explain the beneficial aspects of many plant compounds?

Medicine has utilised plant-based treatments for millennia, but precisely how they work is unclear. One approach is to use a thermodynamic viewpoint that life arose by dissipating geothermal and/or solar potential. Hence, the ability to dissipate energy to maintain homeostasis is a fundamental principle in all life, which can be viewed as an accretion system where layers of complexity have built upon core abiotic molecules. Many of these compounds are chromophoric and are now involved in multiple pathways. Plants have further evolved a plethora of chromophoric compounds that can not only act as sunscreens and redox modifiers, but also have now become integrated into a generalised stress adaptive system. This could be an extension of the dissipative process. In animals, many of these compounds are hormetic, modulating mitochondria and calcium signalling. They can also display anti-pathogen effects. They could therefore modulate bioenergetics across all life due to the conserved electron transport chain and proton gradient. In this review paper, we focus on well-described medicinal compounds, such as salicylic acid and cannabidiol and suggest, at least in animals, their activity reflects their evolved function in plants in relation to stress adaptation, which itself evolved to maintain dissipative homeostasis.