Efficacy of dioic acid compared with hydroquinone in the treatment of melasma

Melasma: A Step-by-Step Approach Towards a Multimodal Combination Therapy

Melasma is a common challenge in the field of pigmentary skin disorders, exerting a significant emotional and psychosocial burden on patients. The persistent and recurring nature of melasma complicates its management in routine clinical practice. This comprehensive review outlines a stepwise, practical approach encompassing diagnostic, preventive and therapeutic strategies for the management of melasma. A thorough exploration of aggravating and exacerbating factors, including sun exposure, hormonal imbalances, photosensitizing medication and cosmetics, is essential for a holistic assessment of the disease. With an emphasis on consistent and effective photoprotection, initial topical treatment modalities target the melanin production and/or the transfer of melanosomes to keratinocytes. Topical tyrosine inhibitors emerge as the first choice for reducing and preventing hyperpigmentation, with compounds such as thiamidol or tranexamic acid (TXA) being preferred for their safety profile over hydroquinone (HQ), kojic acid and arbutin. Combination with chemical peels can further enhance the therapeutic efficacy, even in cases with resistant melasma. In more severe cases, laser- and light-based interventions may be considered, but with the caveat of the likelihood of recurrence within 3-6 months. Assisted TXA delivery, via either fractional non-ablative laser or microneedling techniques, can further improve clinical outcomes. In conclusion, an optimal melasma management strategy is a multimodal approach, which includes effective photoprotection and a mix of different topical treatments targeting melanin synthesis, the anti-inflammatory environment, senescence and vascularity. Complementary procedures, such as chemical peels, and laser, light-based or microneedling procedures, with or without TXA, can further expedite melanin clearance in more severely affected instances. Individual discussions with patients regarding treatment expectations, recurrence likelihood and potential side effects are paramount to a comprehensive and successful therapeutic journey.

Different therapeutic approaches in melasma: advances and limitations

Melasma is a chronic hyperpigmentation skin disorder that is more common in the female gender. Although melasma is a multifactorial skin disorder, however, sun-exposure and genetic predisposition are considered as the main etiologic factors in melasma occurrence. Although numerous topical and systemic therapeutic agents and also non-pharmacologic procedural treatments have been considered in melasma management, however, the commonly available therapeutic options have several limitations including the lack of sufficient clinical effectiveness, risk of relapse, and high rate of unwanted adverse drug reactions. Recruitment of nanotechnology for topical drug delivery in melasma management can lead to enhanced skin penetration, targeted drug delivery to the site of action, longer deposition at the targeted area, and limit systemic absorption and therefore systemic availability and adverse drug reactions. In the current review, first of all, the etiology, pathophysiology, and severity classification of melasma have been considered. Then, various pharmacologic and procedural therapeutic options in melasma treatment have been discussed. Afterward, the usage of various types of nanoparticles for the purpose of topical drug delivery for melasma management was considered. In the end, numerous clinical studies and controlled clinical trials on the assessment of the effectiveness of these novel topical formulations in melasma management are summarized.

Topical and Systemic Therapies in Melasma: A Systematic Review

Introduction

Melasma is an acquired disorder, which presents with well-demarcated, brown-colored hyperpigmented macules, commonly involving the sun-exposed areas such as the face. It is a chronic and distressing condition, affecting the patients' quality of life, and has been conventionally treated with "first-line" agents including hydroquinone (HQ) alone or as a part of a triple combination cream (TCC), while "second-line" options include chemical peels, and third line options include laser therapy.

Materials and Methods

A systematic search was performed for all topical and systemic treatments for melasma up till May 4, 2021, using the PubMed and EMBASE databases, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. The search terms "melasma" and "treatment" were used to search for the relevant articles on both these databases, and a total of 4020 articles were identified. After removing the duplicate entries and screening the titles, abstracts, and full-text articles, we identified 174 randomized controlled trials (RCTs) or controlled clinical trials.

Results

Based on our review, HQ, TCCs, sunscreens, kojic acid (KA), and azelaic acid receive grade A recommendation. Further large-scale studies are required to clearly establish the efficacy of topical vitamin C, resorcinol, and topical tranexamic acid (TXA). Several newer topical agents may play a role only as an add-on or second-line drugs or as maintenance therapy. Oral TXA has a strong recommendation, provided there are no contraindications. Procyanidins, Polypodium leucotomos (PL), and even synbiotics may be taken as adjuncts.

Discussion

Several newer topical and systemic agents with multimodal mechanisms of action have now become available, and the balance seems to be tipping in favor of these innovative modalities. However, it is worth mentioning that the choice of agent should be individualized and subject to availability in a particular country.

Efficacy and safety of topical agents in the treatment of melasma: What's evidence? A systematic review and meta-analysis

BACKGROUND

Various topical agents have been used to treat melasma; however, a large-scale evaluation among the currently available treatment is lacking.

OBJECTIVES

The aim of this study was to evaluate the efficacy and safety of topical agents for melasma.

METHODS

The MEDLINE, Embase, Web of Science, Cochrane, and Alt-Healthwatch databases were searched in November 2021. Original studies that reported pre- and post-treatment Melasma Area Severity Index (MASI)/modified Melasma Area Severity Index (mMASI) scores and/or adverse effects (AEs) were eligible for inclusion. The main outcome was the efficacy analyzed by the changes in the pre- and post-treatment with standardized mean difference (SMD) of MASI/mMASI scores; the AEs were calculated with incidence proportion by the reported percentage of skin irritations.

RESULTS

A total of 45 studies (2359 patients) and 55 studies (4539 patients) met the inclusion criteria for efficacy and AEs, respectively. Hydroquinone (HQ) monotherapy (SMD -1.3, 95% CI [-1.6 to -1.0]), HQ-containing combination therapy (-1.4, [-1.7 to -1.1]), cysteamine (-1.6, [-2.0 to -1.2]), tranexamic acid (-1.5, [-2.0 to -1.1]), azelaic acid (-1.3, [-1.7 to -1.0]), and kojic acid (-0.9, [-1.3 to -0.5]) demonstrated comparable efficacy, while zinc sulfate did not exhibit statistically significant improvement (-1.2, [-2.7 to 0.4]). HQ-containing combination therapy (50.9%) and cysteamine (42.2%) demonstrated the highest incidence of irritation, while azelaic acid (18.7%), kojic acid (5.3%), and tranexamic acid (0.8%) revealed a lower risk.

CONCLUSIONS

In this meta-analysis, non-HQ agents except zinc sulfate may be considered as an alternative to HQ-containing agents. However, treatment should be guided by patient's tolerance, availability, and physicians' experience.

Understanding Melasma-How Can Pharmacology and Cosmetology Procedures and Prevention Help to Achieve Optimal Treatment Results? A Narrative Review

Melasma is a chronic skin condition that involves the overproduction of melanin in areas exposed to ultraviolet radiation. Melasma treatment is long-term and complicated with recurrence and resistance to treatment. The pathogenesis of melasma is highly complex with multiple pathologies occurring outside of the skin pigment cells. It includes photoaging, excessive melanogenesis, an increased number of mast cells, increased vascularization, and basement membrane damage. In addition, skin lesions related to melasma and their surrounding skin have nearly 300 genes differentially expressed from healthy skin. Traditionally, melasma was treated with topical agents, including hydroquinone, tretinoin, glucocorticosteroids and various formulations; however, the current approach includes the topical application of a variety of substances, chemical peels, laser and light treatments, mesotherapy, microneedling and/or the use of systemic therapy. The treatment plan for patients with melasma begins with the elimination of risk factors, strict protection against ultraviolet radiation, and the topical use of lightening agents. Hyperpigmentation treatment alone can be ineffective unless combined with regenerative methods and photoprotection. In this review, we show that in-depth knowledge associated with proper communication and the establishment of a relationship with the patient help to achieve good adherence and compliance in this long-term, time-consuming and difficult procedure.

Medical therapies for Melasma

Melasma is a common malady affecting all races with a higher incidence in Hispanics, Middle Eastern, Asians and African origin females (Fitzpatrick skin phototypes III-V). Women are affected much more often than men. Melasma remains a significant cause of cosmetic morbidity and psychosocial embarrassment affecting quality of life necessitating effective and reliable treatment. Unfortunately, treatment remains unsatisfactory due to limited efficacy, adverse effects and relapses after stopping treatment. Although chemical peels, laser and light therapies and dermabrasion may have utility, the evidence available for their efficacy is limited and they often cause post inflammatory hyperpigmentation particularly in individuals with darker skin types. Medical therapies remain mainstay in the management of melasma. The triple combination, hydroquinone 4%, tretinoin 0.05% and fluocinolone acetonide 0.01% (Triluma, Galderma, Ft. Worth Texas, often modified incorporating different corticosteroids) remains the only US FDA approved treatment for melasma and is the gold standard due its demonstrated efficacy across ethnicities. Oral tranexamic acid alone or in combination with other modalities has also shown significant efficacy. Several cosmeceuticals and botanical extracts used as skin lightening agents have been demonstrated to be useful. Physical sunscreens containing zinc oxide, iron oxide, titanium dioxide, and silicones provide photoprotective and camouflage effect. We propose that a multimodality approach to the treatment of melasma is the most effective treatment approach. This review is focused on the medical therapies for melasma.

Alterations of the pigmentation system in the aging process

Human skin aging is a natural phenomenon that results from continuous exposure to intrinsic (time, genetic factors, hormones) as well as extrinsic factors (UV exposure, pollution, tobacco). In areas that are frequently exposed to the sun, photoaging blends with the process of intrinsic aging, resulting in an increased senescent cells number and consequently accelerating the aging process. The severity of photodamage depends on constitutional factors, including skin phototype (skin color, tanning capacity), intensity, and duration of sunlight/UV exposure. Aging affects nearly every aspect of cutaneous biology, including pigmentation. Clinically, the phenotype of age pigmented skin has a mottled, uneven color, primarily due to age spots, with or without hypopigmentation. Uneven pigmentation might be attributed to the hyperactivation of melanocytes, altered distribution of pigment, and turnover. In addition to direct damage to pigment-producing cells, photodamage alters the physiological crosstalk between keratinocytes, fibroblasts, endothelial cells, and melanocytes responsible for natural pigmentation homeostasis. Interestingly, age-independent diffuse expression of senescence-associated markers in the dermal and epidermal compartment is also associated with vitiligo, suggesting that premature senescence plays an important role in the pathology.

Clinical evaluation of the efficacy of a facial serum containing dioic acid, glycolic acid, salicylic acid, LHA, citric acid, and HEPES in treating post-inflammatory hyperchromia and controlling oily skin in patients with acne vulgaris

BACKGROUND

Acne is a chronic disease that affects the pilosebaceous follicle and is characterized by the presence of non-inflammatory and/or inflammatory lesions, affecting both adolescents and adults. Inflammatory acne lesions are capable to increase their melanin production and promote a post-inflammatory hyperchromia.

AIMS

To assess the efficacy of a serum containing dioic acid, glycolic acid, salicylic acid, LHA, citric acid, and HEPES in treating post-inflammatory hyperpigmentation and controlling skin oiliness in Brazilian patients with acne vulgaris.

PATIENTS/METHODS

A single-center, prospective, open-label clinical study included 42 subjects, from both genders, presenting acne (grade I or II), oily skin and a clinical diagnosis of acne post-inflammatory hyperpigmentation. The study was conducted for 56 days, with clinical (skin quality and the number of post-inflammatory hyperchromic lesions) and instrumental (Sebumetry) evaluations after 7, 28, and 56 days of treatment. Standardized pictures were obtained using a VISIA-6^® device.

RESULTS

A significant decrease in the grade of post-inflammatory hyperchromic lesions was observed after 28 and 56 days, while the number of lesions decreases by 29.4% after 56 days (p < 0.001). Sebumetry values showed a significant decrease of 30.7% in the oiliness after 7 days of treatment, and then stable during the study conduction period of 56 days (p < 0.001 for all measurements).

CONCLUSIONS

The daily treatment using the investigational product showed an interesting decrease both in the grade and the number of post-inflammatory hyperchromia acne lesions after 56 days, and in the oiliness after 7 days, being stable for all study period.

Combination treatment algorithm for pigmentary disorders of the face: A prospective observational study in Asian patients

BACKGROUND

Most patients with facial pigmentary disorders have multiple disorders. However, there is no definitive treatment algorithm improving various pigmentary disorders simultaneously.

OBJECTIVES

To investigate the clinical efficacy and safety of the combination of the Q-switched alexandrite and the carbon dioxide lasers with ZO SKIN HEALTH^Ⓡ for facial pigmentary disorders.

PATIENTS/METHODS

This prospective observational study enrolled 251 patients with at least one facial pigmentary disorder. We assessed treatment efficacy and investigated which disorders were most responsive to combination treatment and the relationship between doctors' skills, outcomes, and dropout rates.

RESULTS

There were 246 patients with lentigo senilis, 186 with moles, 79 with melasma, 53 with seborrheic keratosis, 17 with acquired dermal melanocytosis (ADM), and 16 with freckles. Overall, 227 patients completed treatment. Post-treatment outcomes were excellent in 97, good in 113, fair in 17, and poor in 0 patients. Freckles were the most responsive, and ADM was the least responsive. Patient withdrawal and treatment outcomes did not differ significantly based on the doctors' skills. Overall, 3.2% of patients had adverse events.

CONCLUSIONS

Our combination algorithm improved several pigmentary disorders of the face simultaneously, regardless of the doctors' proficiency level.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

Study on the Chemical Composition, Enzyme Inhibition and Antioxidant Activity of Ziziphora taurica subsp. cleonioides

Ziziphora is a plant used in Turkish and Iran traditional medicine for its antibacterial activity, sedative and stomach soothing properties. Although the chemical profile of the essential oil of different Ziziphora species is well documented, data regarding plant extracts are incomplete. In this study extracts from Ziziphora taurica subsp. cleonioides were obtained using ethyl acetate, methanol and water and the chemical profile of the aerial part of the plant was elucidated. Among the compounds identified, rosmarinic acid was the most abundant (3375.67 ± 38.02 μg/mL), at the extract of methanol, followed by chlorogenic acid (3225.10 ± 16.44). Enzyme inhibition activity against α-amylase and tyrosinase was also estimated. The ethyl acetate extract showed the highest α-amylase activity (1.95 ± 0.04 mg/mL), while the best anti-tyrosinase activity was calculated for the methanolic extract (1.25 ± 0.01 mg/mL). In addition, total phenolic, flavonoid content and antioxidant activity were evaluated. According to our results, bioactivity of the plant is of great interest, nonetheless, at the same time, it is strongly depended on the solvent used during the extraction process. Our data suggest that the plant under study may be an important source to consider against metabolic, skin pigmentation and oxidative stress related disorders.

Effective Tyrosinase Inhibition by Thiamidol Results in Significant Improvement of Mild to Moderate Melasma

Melasma is a pigmentary disorder characterized by hyperpigmented patchy skin in sun-exposed areas, especially the face. Treatment of melasma can be challenging because long-term therapy is required, reoccurrence is common, and existing therapies are insufficient and unsatisfactory. To investigate new treatment options, we performed an exploratory double-blinded, randomized split-face study to assess the efficacy of the tyrosinase inhibitor Thiamidol compared to hydroquinone in women with mild to moderate melasma. After 12 weeks, modified Melasma Area and Severity Index scores significantly improved on both the Thiamidol-treated and the hydroquinone-treated sides of the face. Additionally, Thiamidol treatment improved modified Melasma Area and Severity Index scores significantly better than hydroquinone, and more subjects improved following treatment with Thiamidol (79%) compared with hydroquinone (61%). During treatment, no subjects displayed worsening of modified Melasma Area and Severity Index scores on the Thiamidol-treated side, while approximately 10% of the subjects showed a worsening of modified Melasma Area and Severity Index scores on the hydroquinone-treated side. All subjects routinely used sunscreens and consistent results were obtained in low and in high UV ambient conditions. Subjects rated the efficacy of the Thiamidol formulation significantly better with regard to overall decreased intensity of dark spots and their overall appearance throughout the study. Thiamidol was well-tolerated and well-perceived and represents an effective agent to reduce hyperpigmentation.

Medical Management of Melasma: A Review with Consensus Recommendations by Indian Pigmentary Expert Group

Melasma is one of the most common hyperpigmentary disorders found mainly in women and dark-skinned patients. Sunlight, hormones, pregnancy, and genetics remain the most implicated in the causation of melasma. Although rather recalcitrant to treatment, topical agents such as hydroquinone, modified Kligman's Regime, azelaic acid, kojic acid, Vitamin C, and arbutin still remain the mainstay of therapy with sun protection being a cornerstone of therapy. There are several new botanical and non botanical agents and upcoming oral therapies for the future. There is a lack of therapeutic guidelines, more so in the Indian setup. The article discusses available evidence and brings forward a suggested treatment algorithm by experts from Pigmentary Disorders Society (PDS) in a collaborative discussion called South Asian Pigmentary Forum (SPF).

Evidence-based Review, Grade of Recommendation, and Suggested Treatment Recommendations for Melasma

Treatment of melasma is known to be less satisfactory, often incomplete, and relapse is frequent. Although many treatment options are available, they are either known to be unsafe on long-term use or their long-term safety profile is unknown. Patients often use various drugs, even topical steroid-based preparation without any medical supervision for long period of time, making the skin unsuitable for many of the drugs available. Thus, there has been gross disparity among the treating physician about what drugs and what regimen are best suitable for various categories of melasma patients and in different situations. With this background, numerous newer drugs, mostly combinations of some proprietary molecules or even unknown plant extracts, have flooded the market for the management of melasma. Information on efficacy or safety of these products are almost unknown. Studies on Asian people, especially Indian population, are far less commonly available. Therapeutic guideline for use on Indian patients with melasma is almost missing. Extrapolation of data from Caucasian people for use on Asian people may not be scientifically justifiable because Caucasian and Asian people are known to have inherent difference in their response as well as tolerance to the drugs used for melasma. With this background, we have extensively evaluated, following a strict, scientifically designed protocol, all the available studies on melasma management till May 2016 and prepared this document on level of evidence, grade of recommendation and suggested therapeutic guideline for melasma as per the method proposed by Oxford Centre of Evidence-Based Medicine. Various ethical, social, logical, regional, and economic issues in the context of Indian and similar populations were given due importance while preparing the suggested therapeutic recommendation.

The first clinical experience on efficacy of topical flutamide on melasma compared with topical hydroquinone: a randomized clinical trial

Background

Treatment of melasma is unsatisfactory most of the times. Hormonal role is shown to exist in pathogenesis of the melasma, and sex-hormone related drugs may have an effect on melasma.

Aim

To investigate efficacy of 1% flutamide cream versus 4% hydroquinone cream on melasma.

Methods

In a parallel randomized clinical trial, 74 women with melasma were allocated to receive a sunscreen along with 4% hydroquinone cream or 1% flutamide cream. Melasma Area and Severity Index (MASI), mexameter melanin assay, and patient satisfaction were investigated.

Results

Mean age of the participants was 33.8 years. Mean length of time suffering from Melasma was 96.3 months. The subjects reported in average 1.1 hours per day of exposure to sunlight. Mean standardized total patient satisfaction score was 28.8 (standard deviation [SD] 17.2) in flutamide group patients versus 18 (SD 15.5) in control group (P<0.01). Regardless of treatment group, the skin darkness assessed upon MASI scales was reduced over the treatment course (P<0.001). Using mixed effects, longitudinal modeling showed better treatment efficacy based on MASI scale for flutamide group compared to the hydroquinone group (P<0.05). However, longitudinal analysis of mexameter scores did not reveal any significant difference in melanin measurements between flutamide and hydroquinone.

Conclusion

Topical flutamide appeared as effective as topical hydroquinone in treating melasma using mexameter assessment but with a better MASI improvement trend and higher patient satisfaction in flutamide treatment versus topical hydroquinone. As the present study is possibly the first clinical experience on efficacy of topical flutamide on melasma, it would be quite unreasonable to recommend clinical use of it before future studies replicate the results on its efficacy and safety.

Evaluation of the efficacy and safety of combinations of hydroquinone, glycolic acid, and hyaluronic acid in the treatment of melasma

BACKGROUND

Various treatments are currently available for melasma. However, results are often disappointing.

OBJECTIVES

1 To assess the efficacy and safety of combinations of hydroquinone, glycolic acid, and hyaluronic acid in the treatment of melasma after topical application. 2 To evaluate the dermoscopy as a tool in diagnosis and follow-up of melasma treatment.

PATIENTS AND METHODS

One hundred patients with mild, moderate-to-severe melasma were divided into five groups. Group I (twenty patients were treated with cream formula containing 4% hydroquinone), group II (twenty patients were treated with cream formula containing 4% hydroquinone + 10% glycolic acid), group III (twenty patients were treated with cream formula containing 4% hydroquinone + 0.01% hyaluronic acid), group IV (twenty patients were treated with cream formula containing 4% hydroquinone + 10% glycolic acid + 0.01% hyaluronic acid), and group V (twenty patients were treated with placebo cream). All patients were subjected to dermoscopic examination and digital photographs before and after treatment. The response and side effects were evaluated.

RESULTS

Groups I, III, and IV showed highly significant changes in modified Melasma Area and Severity Index (mMASI) score after using the treatment. Group II showed significant change in mMASI score after using the treatment. The side effects were more reported in group II, followed by group IV, followed by group I, followed by group III. There was highly significant difference between the dermoscopic color findings before and after treatment. Vascularization was another dermoscopic finding.

CONCLUSION

A cream formula containing 4% hydroquinone + 10% glycolic acid + 0.01% hyaluronic acid was very effective in treatment of melasma with tolerable side effects. Dermoscope is a valuable noninvasive tool in the diagnosis and follow-up of melasma treatment.

Rationale of using hypopigmenting drugs and their clinical application in melasma

Among the pigmentary disorders, melasma is the prototype disorder characterized by hyperpigmentation. Although, conventionally, triple combination creams are used, there is a need for alternatives to hydroquinone as the drug has restrictions on its widespread use. This needs an understanding of the steps involved in the melanogenesis and the drugs that inhibit the key steps. The data on in vitro inhibition need to be then translated into clinical in vivo results, before a rationale compounded fixed drug preparation is marketed that inhibits the major steps in the pigmentation pathway. There is also a need to look for drugs that are superior to hydroquinone, as only then will they have a meaningful clinical utility. For now, a few drugs like deoxyarbutin, ellagic acid, dioic acid, n-butylresorcinol and azelaic acid have such properties in clinical trials, while metformin is a recent addition.

The evaluation of depigmenting efficacy in the skin for the development of new whitening agents in Korea

In this review, the evaluation methods for the screening of depigmenting substrates were investigated. For this purpose, the evaluation method of tyrosinase, a key enzyme of melanin biosynthesis, is most frequently used, but evaluating methods based on the regulation of cellular signal transfer factors or the inhibition of melanosome transfer have also been developed. Evaluation of the depigmenting effect using melanocytes is complex. It has the advantage of being capable of analysing overall effects on melanin biosynthesis at cellular levels. Before the final clinical testing of depigmenting agents, in vitro testing should be conducted to confirm the depigmenting efficacy and safety. Clinical studies for depigmenting agents can be used to investigate the prevention of melanin biosynthesis and to determine whether melanin disappears from skin. Therefore, the most appropriate protocol has to be employed, depending on the mechanism of action of the depigmenting agent.

Inhibitory effects of resveratrol analogs on mushroom tyrosinase activity

Skin pigmentation disorders typically involve an overproduction or uneven distribution of melanin, which results in skin spots. Resveratrol can inhibit tyrosinase, the active enzyme in the synthesis of melanin, but it does not inhibit the synthesis of melanin to an extent that enables its use alone as a skin whitening agent in pharmaceutical formulations, so its use as a coadjuvant in treatment of hyperpigmentation is suggested. Six resveratrol analogs were tested for tyrosinase inhibitory activity in vitro. Among the analogs tested, compound D was the most powerful tyrosinase inhibitor (IC(50) = 28.66 µg/mL), two times more active than resveratrol (IC(50) = 57.05 µg/mL), followed by the analogs A, E, B, F and C, respectively. This demonstrated that the hydroxylation at C4' on the phenolic ring was the molecular modification with most importance for the observed activity.

New horizons in treating disorders of hyperpigmentation in skin of color

Pigmentary abnormalities are among the most common reasons why patients with skin of color visit a dermatologist. Hydroquinone has been a cornerstone for the treatment of hyperpigmentation; however, concerns regarding adverse effects have prompted a search for alternative agents. Some promising topical treatments include soy, licorice, rucinol, mulberry, niacinamide, ellagic acid, resveratrol, and dioic acid. Oral agents, primarily used for the prevention of postprocedural hyperpigmentation, include procyanidins, tranexamic acid, and Polypodium leucotomos. Advances in Q-switched lasers, intense pulse light, fractional photothermolysis, and the advent of tretinoin peeling add to the clinician's armamentarium for treating hyperpigmentation.

Postinflammatory hyperpigmentation: etiologic and therapeutic considerations

Postinflammatory hyperpigmentation (PIH) is a reactive hypermelanosis and sequela of a variety of inflammatory skin conditions. PIH can have a negative impact on a patient's quality of life, particularly for darker-skinned patients. Studies show that dyschromias, including PIH, are one of the most common presenting complaints of darker-skinned racial ethnic groups when visiting a dermatologist. This is likely due to an increased production or deposition of melanin into the epidermis or dermis by labile melanocytes. A variety of endogenous or exogenous inflammatory conditions can culminate in PIH and typically most epidermal lesions will appear tan, brown, or dark brown while dermal hypermelanosis has a blue-gray discoloration. Depigmenting agents target different steps in the production of melanin, most commonly inhibiting tyrosinase. These agents include hydroquinone, azelaic acid, kojic acid, arbutin, and certain licorice (glycyrrhiza) extracts. Other agents include retinoids, mequinol, ascorbic acid (vitamin C), niacinamide, N-acetyl glucosamine, and soy, and these products depigment by different mechanisms. Certain procedures can also be effective in the treatment of PIH including chemical peeling and laser therapy. It is important to note that these same therapeutic modalities may also play a role in causing PIH. Lastly, those lesions that are not amenable to medical or surgical therapy may experience some improvement with cosmetic camouflage.