Prebiotic Combinations Effects on the Colonization of Staphylococcal Skin Strains.

BACKGROUND: An unbalanced skin microbiota due to an increase in pathogenic vs. commensal bacteria can be efficiently tackled by using prebiotics. The aim of this work was to identify novel prebiotic combinations by exerting species-specific action between S. aureus and S. epidermidis strains. METHODS: First, the antimicrobial/antibiofilm effect of Xylitol-XYL and Galacto-OligoSaccharides-GOS combined with each other at different concentrations (1, 2.5, 5%) against S. aureus and S. epidermidis clinical strains was evaluated in time. Second, the most species-specific concentration was used to combine XYL with Fructo-OligoSaccharides-FOS, IsoMalto-Oligosaccharides-IMO, ArabinoGaLactan-LAG, inulin, dextran. Experiments were performed by OD600 detection, biomass quantification and LIVE/DEAD staining. RESULTS: 1% XYL + 1% GOS showed the best species-specific action with an immediate antibacterial/antibiofilm action against S. aureus strains (up to 34.54% ± 5.35/64.68% ± 4.77) without a relevant effect on S. epidermidis. Among the other prebiotic formulations, 1% XYL plus 1% FOS (up to 49.17% ± 21.46/37.59% ± 6.34) or 1% IMO (up to 41.28% ± 4.88/36.70% ± 10.03) or 1% LAG (up to 38.21% ± 5.31/83.06% ± 5.11) showed antimicrobial/antibiofilm effects similar to 1% XYL+1% GOS. For all tested formulations, a prevalent bacteriostatic effect in the planktonic phase and a general reduction of S. aureus biofilm formation without loss of viability were recorded. CONCLUSION: The combinations of 1% XYL with 1% GOS or 1% FOS or 1% IMO or 1% LAG may help to control the balance of skin microbiota, representing good candidates for topic formulations.

Protective Role of Nutritional Plants Containing Flavonoids in Hair Follicle Disruption: A Review.

Hair loss is a disorder in which the hair falls out from skin areas such as the scalp and the body. Several studies suggest the use of herbal medicine to treat related disorders, including alopecia. Dermal microcirculation is essential for hair maintenance, and an insufficient blood supply can lead to hair follicles (HF) diseases. This work aims to provide an insight into the ethnohistorical records of some nutritional compounds containing flavonoids for their potential beneficial features in repairing or recovering from hair follicle disruption. We started from a query for "alopecia" OR "hair loss" AND "Panax ginseng C.A. Mey." (or other six botanicals) terms included in Pubmed and Web of Sciences articles. The activities of seven common botanicals introduced with diet (Panax ginseng C.A. Mey., Malus pumila Mill cultivar Annurca, Coffea arabica, Allium sativum L., Camellia sinensis (L.) Kuntze, Rosmarinum officinalis L., Capsicum annum L.) are discussed, which are believed to reduce the rate of hair loss or stimulate new hair growth. In this review, we pay our attention on the molecular mechanisms underlying the bioactivity of the aforementioned nutritional compounds in vivo, ex vivo and in vitro studies. There is a need for systematic evaluation of the most commonly used plants to confirm their anti-hair loss power, identify possible mechanisms of action, and recommend their best adoption.

Milk thistle and olive extract: old substances with a new mission against sun-induced skin damage.

BACKGROUND: Natural antioxidants represent an effective option in the prevention and/or improvement of ultraviolet radiations (UVR)-induced/aggravated skin conditions. UVR cause DNA damage in keratinocytes, directly, in the form of cyclobutane pyrimidine dimers (CPDs), or indirectly, through oxidative stress production. Failure of the repair system can result in genetic mutations primarily responsible for the initiation of NMSCs. The aim of our study was to evaluate the in vitro protective effect of milk thistle and olive purified extracts on cultured keratinocytes after solar simulator irradiations (SSR). METHODS: Immortalized keratinocytes were pre-incubated with different concentrations of milk thistle and olive purified extracts, and irradiated with increasing doses of SSR. Thereafter, CPDs and p53 expression were evaluated to assess DNA damage, whereas cellular antioxidants consumption and lipid membranes peroxidation were measured to analyze oxidative stress. RESULTS: The study substances were well tolerated by cells and displayed good cytoprotective and antioxidant activities, being milk thistle dry extract more effective in limiting the direct DNA damage, and olive extract particularly able to reduce lipid membrane peroxidation and to increase cellular antioxidants. CONCLUSIONS: Both study substances can be defined as safe compounds, showing differential cytoprotective and antioxidant activities and might represent interesting options for NMSCs chemoprevention.

A Water-Soluble Microencapsulated Milk Thistle Extract as Active Ingredient for Dermal Formulations.

The choice of formulation is often of crucial importance in order to obtain a pharmaceutical product for the administration of poorly soluble drugs. Recently, a new water-soluble microparticulate powder form (MTE-mp) for the oral administration of a high functionality/low solubility silymarin rich milk thistle extract (MTE) has been developed. Findings showed that extract-loaded microparticles by spray-drying were produced with high and reproducible yields and encapsulation efficiency. The in vitro dissolution and permeation rates of silymarin were dramatically improved with respect to the raw material, and also enhanced the silymarin anti-inflammatory abilities. Given these successful results, the new MTE-mp delivery system has been proposed as an active ingredient for dermal applications. The aim of this research was the design and development of two topical formulations, hydrogel and emulgel (O/W emulsion), containing the MTE-mp delivery system or MTE raw extract. All the formulations were compared to each other in terms of handling and incorporation amount of the active ingredient during the productive process. Moreover, the addition to the emulgel of lecithin (L) as enhancer of permeation was tested. The MTE-mp ingredient that resulted was stable and more-easily incorporated both in hydrogel and emulgel than raw MTE extract, obtaining the best permeation profile for MTE-mp from emulgel with the addition of L. The obtained results confirm that the MTE-mp system could be used as a stable, water-soluble, and easy-handling functional ingredient, giving the opportunity to develop new strategies for MTE delivery in health products.

Natural dietary antioxidants containing flavonoids modulate keratinocytes physiology: In vitro tri-culture models.

ETHNOPHARMACOLOGICAL RELEVANCE: Several traditional medicinal herbs are widely used for dermatologic and cosmetic preparations. The beneficial skin repair activity is detected in various phases of wound-healing process, such as cell-cell, cell-matrix interactions or collagen synthesis. AIM OF THE STUDY: The study assessed the effects of Opuntia ficus-indica (L.) Mill. (Opuntia) and Milk Thistle (MT) (Silybum marianum (L.) Gaerth) on adult keratinocytes (HaCaT) functioning under basal condition or in the presence of mechanical damage (wounded cells). MATERIALS AND METHODS: The role of the natural compounds was tested on HaCaT grown in mono-culture and tri-culture configurations. In tri-cultures models, HaCaT were treated with the conditioned media (CM) obtained by Human Normal Dermal Fibroblast (NHDF) and Human Dermal Microvascular Endothelial cells (HMVEC) co-cultures. Specifically, were tested cell viability, oxidative stress mechanisms (cytokines release and lipid peroxidation) and cellular remodelling (growth factors release or metalloproteinase modulation). Moreover, the migratory potential of HaCaT was analysed by the use of wound healing in vitro assay. RESULTS: Opuntia and MT differently modified the metabolism (EGF, MMP-9), and the migratory properties of HaCaT both under physiological conditions or upon mechanical damage (wounded cells). Moreover, both compounds modulated HaCaT response to oxidative stress. The response to the natural compounds were modified, and in some cases potentiated, in tri-culture configuration systems. CONCLUSIONS: The data demonstrated that in vitro tri-culture approach is suitable to characterize the role of natural compounds on the complex communication between dermal-epidermal cellular components and microvascular endothelium. Specifically, Opuntia and MT are good alternatives to synthetic compounds in skin repair promotion.

Serenoa repens and N-acetyl glucosamine/milk proteins complex differentially affect the paracrine communication between endothelial and follicle dermal papilla cells.

Current treatments for hair follicle (HF) disruption are based on 5-α reductase inhibitors and prostaglandin modulators. Botanicals and nutraceutical compounds interfere with hair loss or stimulate its partial regrowth. Here, we used in vitro cocultures to investigate the activity of Serenoa repens ( SR) and N-acetyl glucosamine + milk proteins (NAG/Lac) on the paracrine interactions between human microvascular endothelial cells (HMVEC) and HF dermal papilla cells (FDPC). Both SR and NAG/Lac-induced endothelial tubulogenesis were enhanced by FDPC. SR promoted proliferation of both the cell types, while NAG/Lac was effective on endothelium. Vascular endothelial growth factor production, enhanced by SR, was further augmented by FDPC. In FDPC 5-α reductase-II and ß-catenin expressions were modified by SR and less by NAG/Lac, with no additional effect by HMVEC. SR and NAG/Lac prevented lipid peroxidation, whereas NAG/Lac was effective on interleukin 1ß production. Finally, SR and NAG/Lac differentially affected HMVEC permeability and tight junction proteins content. These data provide a mechanistic background for the potential use of these compounds as promoters of HF vascularization.

The anti-inflammatory and antioxidant properties of 1,2-decanediol and willow bark extract in lipopolysaccharide-stimulated keratinocytes.

BACKGROUND: 1,2-Decanediol (S-Mal) is an organic compound belonging to the 1,2-alkanediol family, with two hydroxyl groups located on the first and second carbon of the alkane chain, probably responsible for the enhanced anti-bacterial efficacy. The willow bark total extract (W-Mal) has been used since thousands of years as an herbal remedy for its antipyretic, analgesic, anti-inflammatory and anti-microbial activities. S-Mal is used in cosmetic preparations, whether W-Mal can be topically or systemically administered. Aim of our study was to evaluate in vitro the anti-inflammatory and antioxidant properties of S-Mal and W-Mal, singularly or in combination, in LPS-stimulated keratinocytes. METHODS: The possible toxic effect of S-Mal and W-Mal was assessed through analysis of cell viability 24 hours after treatment. The anti-inflammatory and antioxidant activities were evaluated by measuring IL-8, TNF-α and IL-1ß production as well as cellular antioxidants (GSH and NADPH) consumption, 24 and 48 hours, respectively, after LPS stimulation. RESULTS: Both substances resulted able to: 1) increase cell viability (P<0.05); 2) decrease the release of inflammatory mediators (IL-8, TNF-α and IL-1ß) (P<0.05 - P<0.001); and 3) limit the depletion of cellular antioxidants (GSH and NADPH) (P<0.001). CONCLUSIONS: S-Mal and W-Mal have shown a potential cytoprotective activity when used together, and good anti-inflammatory and antioxidant effects when used either singularly or in combination. In light of our results, S-Mal and W-Mal could represent effective and safe options in the management of bacterial-induced or aggravated skin conditions.

Application of Spray Drying Particle Engineering to a High-Functionality/Low-Solubility Milk Thistle Extract: Powders Production and Characterization.

Many natural compounds having antioxidant and anti-inflammatory activity are a potential target for new therapies against chronic inflammatory syndromes. The oral administration of functional herbal supplements may become a prevention strategy or therapy adjuvant for susceptible patients. A case study is our milk thistle (Silybum marianum) extract rich in silymarin complex. A water-soluble microencapsulated powder system was developed by a spray drying technique to improve the poor silymarin bioactivity after oral administration. Sodium carboxymethylcellulose (NaCMC) was employed as coating/swelling polymer matrix and sodium lauryl sulfate (SLS) as the surfactant (1:1:0.05 w/w/w). A H2O/EtOH/acetone (50/15/35 v/v/v) solvent system was used as liquid feed. The microsystems were capable of improving the in vitro dissolution and permeation rates, suggesting an enhancement of bioactivity after oral administration. The microsystems protect the antioxidant activity of silymarin after harsh storage conditions period and do not affect the anti-inflammatory properties of the raw extract (efficient already at lower concentrations of 0.312 mg/mL) to reduce dendritic cells (DCs) inflammatory cytokine secretion after lipopolysaccharide administration. This approach allows managing particle size, surface properties and release of bioactive agents improving the bioactivity of a herbal supplement and is also possibly applicable to many other similar natural products.

Efficacy of Teeth Whitening with a Mouthwash: In Vitro and In Vivo Approaches.

OBJECTIVES: Two different studies were conducted to evaluate the whitening efficacy of a mouthwash versus a placebo using in vitro and in vivomodels. The tested mouthwash was formulated with no oxidizing or abrasive agents containing chlorhexidine (CHX) and polyvinylpyrrolidone (PVP). METHODS: The purpose of the in vitro study was to determine whether the mouthwash formulation OC15AB could reduce the accumulation of staining in an accepted stain model. Bovine central incisors were cut to obtain enamel specimens of ~8 × 8 mm2. The specimens were then immersed in human saliva (room temperature, slight stirring) for one hour to allow a pellicle film to form. They were then placed in contact with a staining solution containing coffee and tea. The amount of stain (tooth color) was quantified photometrically (Minolta C221 colorimeter) using the L* value of the L*a*b* scale. The purpose of the in vivo study was to evaluate the whitening power and tolerability of OC15AB versus a placebo mouthwash in a double-blind, randomized clinical study. In total, 40 subjects were divided randomly into two homogeneous groups. Each group used a different mouthwash (OC15AB or placebo) for 56 consecutive days. During this period, clinical and instrumental parameters, namely variations in tooth color and mucosal and gum alterations, were evaluated. The in vivo study analyses used a two-sided Student's t-test. Evaluations within groups used t-tests for paired data. RESULTS: From the in vitro test, OC15AB had a significant effect in reducing stain accumulation over the entire treatment period. The in vivo test showed that OC15AB was well tolerated and had whitening power in the subjects. OC15AB demonstrated a statistically significant reduction in extrinsic tooth staining from baseline and versus the placebo. CONCLUSIONS: The in vitro and in vivo methods used to investigate the whitening efficacy of the mouthwash formulation produced similar and consistent results. The experimental model used is an important tool in the search for new technologies for teeth whitening. Our preliminary experimental data confirm the possibility of achieving a whitening effect using a mouthwash formulation with no oxidizing or abrasive agents containing CHX and PVP. The formulation tested demonstrated a significant reduction, in vitro and in vivo, in extrinsic tooth staining from baseline and versus the placebo.

Pleiotropic Effects of White Willow Bark and 1,2-Decanediol on Human Adult Keratinocytes.

BACKGROUND: Acne vulgaris is a common skin defect, usually occurring during adolescence, but often it can persist in adults leaving permanent face scarring. Acne is usually treated with topical drugs, oral antibiotics, retinoids, and hormonal therapies, but medicinal plants are increasingly employed. OBJECTIVE: To investigate the protective role of white willow bark (WWB) and 1,2-decanediol (DD) on the damage caused by lipopolysaccharides (LPS) on human adult keratinocytes (HaCaT). METHODS: HaCaT were exposed to LPS alone or in association with WWB and DD. Epidermal viability, metabolic modulation, inflammatory activity, and cell migration were assessed with both common standardized protocols or high-throughput screening systems. RESULTS: The preincubation of HaCaT with WWB and DD (used separately or in combination) differently prevented the alterations induced by LPS on HaCaT in terms of growth factor release (IGF, EGF, VEGF), cytokine production (IL-1α, IL-6, IL-8), or expression of the transcription factor FOXO-I. Moreover, they partially restore wound repair lowered by LPS. CONCLUSIONS: These results suggest that both natural compounds were able to differently affect several functions of LPS-stressed keratinocytes suggesting their potential role for the prevention of acne vulgaris, without adverse effects.

Submicrometric hypromellose acetate succinate particles as carrier for soy isoflavones extract with improved skin penetration performance.

In this study, hypromellose acetate succinate (HPMCAS) stable submicronic particles loaded with a soy isoflavones extract have been obtained by nano spray drying technology. HPMCAS has been used as excipient able to increase both stability and supersaturation levels of the active ingredients hence able to enhance skin penetration performance of genistein and daidzein. The influence of polymer/extract ratio as other process variables, on particle size, morphology and permeation performance, have been investigated. Particles in submicronic range (mean size around 550nm) and narrow size distribution with high encapsulation efficiency (up to 86%) were obtained. HPMCAS was able to improve amorphization of genistein during the atomization process and avoid recrystallization during storage, even in harsh environmental condition. Moreover, the enhanced affinity of the optimized formulations with aqueous media, strongly increased isoflavones penetration through membrane with diffusive properties well-correlated to human skin, up to 10-fold higher than pure soy isoflavones extract raw material.

Dermal-Epidermal Cross-Talk: Differential Interactions With Microvascular Endothelial Cells.

The biological importance of circulatory blood supply and angiogenesis for hair growth is now well recognized, but the their regulatory mechanisms require more mechanistic investigation. In vitro cocultures and tricultures can be successfully employed to greatly improve our knowledge on paracrine crosstalk between cell types that populate the dermal-epidermal interface and cutaneous vasculature. Here we report that human dermal fibroblasts (NHDF) promote viability and proliferation of microvascular endothelial cells (HMVEC), while HMVEC are not mitogenic for NHDF. In triculture setup, conditioned media (CM) obtained by cocultures (HMVEC/NHDF or HMVEC/follicle fibroblasts) differently modulate growth and proliferation of keratinocytes and alter the expression of metabolic and pro-inflammatory markers. In conclusion, tricultures were successfully employed to characterize in vitro dermal-epithelial and endothelial interactions and could integrate ex vivo and in vivo approaches by the use of high-throughput and standardized protocols in controlled conditions. J. Cell. Physiol. 232: 897-903, 2017. © 2016 Wiley Periodicals, Inc.

Effects of flavonoid derivatives on human microvascular endothelial cells.

Some natural compounds, including flavonoids, are active in vasculature re-growth during hair follicle disruption, but their effects have not been yet evaluated directly on microvascular endothelial cells. Skin vascularisation regulates the physiological blood supply required for hair growth and its dysregulation is the basis of several human diseases. Follicle-derived vascular endothelial growth factor (VEGF) release from follicular keratinocytes promotes perifollicular vascularisation and increases follicle and hair size, while blockade of VEGF-mediated angiogenesis leads to impaired hair growth. Here, we tested three flavonoids, namely visnadin (VSD), hesperidin (HSP) and baicalin (BC), on cultured human microvascular endothelial cells (HMEC), comparing their effects with minoxidil (MXD), a synthetic drug broadly used in the treatment of androgenetic alopecia. The response to these compounds was assayed in terms of endothelial survival, proliferation, tubulogenesis and proangiogenic signalling. We show that BC promotes HMEC proliferation, while both VSD and MXD enhance tubulogenesis. Interestingly, only HSP increases VEGFR-2 phosphorylation.

In vitro Percutaneous Absorption of Niacinamide and Phytosterols and in vivo Evaluation of their Effect on Skin Barrier Recovery.

In this study, we evaluated different strategies to optimize the percutaneous absorption of niacinamide (NA) and soy phytosterols (FITO) by making use of solid lipid nanoparticles (SLN) and penetration enhancers, such as the hydrogenated lecithin. The evaluation of the skin permeation of NA and FITO has been effected in vitro using excised human skin (i.e., stratum corneum-epidermis or SCE). Furthermore, we evaluated the in vivo effect that NA and FITO has on skin barrier recovery after the topical application; using the extent of methyl nicotinate (MN)-induced erythema in damaged skin as a parameter to determine the rate of stratum corneum recovery. Results pointed out the importance of these strategies as valid tools for NA and FITO topical delivery. In fact, soy lecithin based formulations were able to increase the percutaneous absorption of the two active ingredients, while SLN guaranteed an interesting delayed and sustained release of FITO. In vivo evaluation showed clearly that the formulation containing both the actives (NA and FITO) is able to recover about 95% of skin barrier integrity eight days after tape stripping. This effect is probably due to the "synergistic effect" of NA and FITO.

Paracrine crosstalk between human hair follicle dermal papilla cells and microvascular endothelial cells.

Human follicle dermal papilla cells (FDPC) are a specialized population of mesenchymal cells located in the skin. They regulate hair follicle (HF) development and growth, and represent a reservoir of multipotent stem cells. Growing evidence supports the hypothesis that HF cycling is associated with vascular remodeling. Follicular keratinocytes release vascular endothelial growth factor (VEGF) that sustains perifollicular angiogenesis leading to an increase of follicle and hair size. Furthermore, several human diseases characterized by hair loss, including Androgenetic Alopecia, exhibit alterations of skin vasculature. However, the molecular mechanisms underlying HF vascularization remain largely unknown. In vitro coculture approaches can be successfully employed to greatly improve our knowledge and shed more light on this issue. Here we used Transwell-based co-cultures to show that FDPC promote survival, proliferation and tubulogenesis of human microvascular endothelial cells (HMVEC) more efficiently than fibroblasts. Accordingly, FDPC enhance the endothelial release of VEGF and IGF-1, two well-known proangiogenic growth factors. Collectively, our data suggest a key role of papilla cells in vascular remodeling of the hair follicle.

The modulatory effect of ellagic acid and rosmarinic acid on ultraviolet-B-induced cytokine/chemokine gene expression in skin keratinocyte (HaCaT) cells.

Ultraviolet radiation (UV) induces an increase in multiple cutaneous inflammatory mediators. Ellagic acid (EA) and rosmarinic acid (RA) are natural anti-inflammatory and immunomodulatory compounds found in many plants, fruits, and nuts. We assessed the ability of EA and RA to modulate IL-1ß, IL-6, IL-8, IL-10, MCP-1, and TNF-α gene expression in HaCaT cells after UVB irradiation. Cells were treated with UVB (100 mJ/cm(2)) and simultaneously with EA (5 µM in 0.1% DMSO) or RA (2.7 µM in 0.5% DMSO). Moreover, these substances were added to the UVB-irradiated cells 1 h or 6 h before harvesting, depending on the established UVB-induced cytokine expression peak. Cytokine gene expression was examined using quantitative real time polymerase chain reaction. RA produced a significant reduction in UVB-induced expression of IL-6, IL-8, MCP-1, and TNF-α when applied at the same time as irradiation. EA showed milder effects compared with RA, except for TNF-α. Both substances decreased IL-6 expression, also when applied 5 h after irradiation, and always produced a significant increase in UVB-induced IL-10 expression. Our findings suggest that EA and RA are able to prevent and/or limit the UVB-induced inflammatory cascade, through a reduction in proinflammatory mediators and the enhancement of IL-10, with its protective function.

Formulation strategies to modulate the topical delivery of anti-inflammatory compounds.

The aim of this study was to assess the ability of some vehicles (emulsion and emulgel), containing hydrogenated lecithin as penetration enhancer, in increasing the percutaneous absorption of the two model compounds dipotassium glycyrrhizinate (DG) and stearyl glycyrrhetinate (SG). Furthermore SG-loaded solid lipid nanoparticles (SLNs) were prepared and the effect of this vehicle on SG permeation profile was evaluated as well. Percutaneous absorption has been studied in vitro, using excised human skin membranes (i.e., stratum corneum epidermis or [SCE]), and in vivo, determining their anti-inflammatory activity. From the results obtained, the use of both penetration enhancers and SLNs resulted in being valid tools to optimize the topical delivery of DG and SG. Soy lecithin guaranteed an increase in the percutaneous absorption of the two activities and a rapid anti-inflammatory effect in in vivo experiments, whereas SLNs produced an interesting delayed and sustained release of SG.

A comparative analysis of the photo-protective effects of soy isoflavones in their aglycone and glucoside forms.

Isoflavones exist in nature predominantly as glucosides such as daidzin or genistin and are rarely found in their corresponding aglycone forms daidzein and genistein. The metabolism and absorption of isoflavones ingested with food is well documented, but little is known about their use as topical photo-protective agents. The aim of this study was to investigate in a comparative analysis the photo-protective effects of isoflavones in both their aglycone and glucoside forms. In human skin fibroblasts irradiated with 60 mJ/cm2 ultraviolet B (UVB), we measured the expression levels of COX-2 and Gadd45, which are involved in inflammation and DNA repair, respectively. We also determined the cellular response to UVB-induced DNA damage using the comet assay. Our findings suggest that both the isoflavone glucosides at a specific concentration and combination with an aglycone mixture exerted an anti-inflammatory and photo-protective effect that prevented 41% and 71% of UVB-induced DNA damage, respectively. The advantages of using either isoflavone glucosides or an aglycone mixture in applications in the field of dermatology will depend on their properties and their different potential uses.

Synergic Effect of Genistein and Daidzein on UVB-Induced DNA Damage: An Effective Photoprotective Combination.

The anti-inflammatory effects and antioxidant activities of individual isoflavones are well established although little is known about the photoprotective effect of their combination. The aim of this study was to investigate the photoprotective effects of different concentrations of genistein and daidzein individually or combined. We measured the expression levels of the cyclo-oxygenase-2 (COX-2) and growth arrest and DNA-damage inducible (Gadd45) genes, which are involved in inflammation and DNA repair, respectively, in BJ-5ta human skin fibroblasts irradiated with 60 mJ/cm(2) UVB. We also determined the cellular response to UVB-induced DNA damage by Comet assay. We report that genistein and daidzein when administered combined, and at a specific concentration and ratio, exerted a synergistic photoprotective effect that was greater than the effect obtained with each isoflavone alone. The results reported herein suggest that low concentrations of genistein and daidzein combined may be good candidate ingredients for protective agents against UV-induced photodamage.