Human skin demonstrates a striking variation in tone and color that is evident among multiple demographic populations. Such characteristics are determined predominantly by the expression of the genes controlling the quantity and quality of melanin, which can alter significantly due to the presence of small nucleotide polymorphism affecting various steps of the melanogenesis process and generally linked to the lighter skin phenotypes. Genetically determined, constitutive skin color is additionally complemented by the facultative melanogenesis and tanning responses; with high levels of melanin and melanogenic factors broadly recognized to have a protective effect against the UVR-induced molecular damage in darker skin. Long-term sun exposure, together with a genetic makeup responsible for the ability to tan or the activity of constitutive melanogenic factors, triggers defects in pigmentation across all ethnic skin types.

However, sun exposure also has well documented beneficial effects that manifest at both skin homeostasis and the systemic level, such as synthesis of vitamin D, which is thought to be less efficient in the presence of high levels of melanin or potentially linked to the polymorphism in the genes responsible for skin darkening triggered by UVR. In this review, we discuss melanogenesis in a context of constitutive pigmentation, defined by gene polymorphism in ethnic skin types, and facultative pigmentation that is not only associated with the capacity to protect the skin against photo-damage but could also have an impact on vitamin D synthesis through gene polymorphism.
Modulating the activities of melanogenic genes, with the focus on the markers specifically altered by polymorphism combined with differential requirements of sun exposure in ethnic skin types, could enhance the applications of already existing skin brightening factors and provide a novel approach toward improved skin tone and health in personalised skincare.

OPEN BIOLOGY Published: 18 December 2019

Human skin is a stratified organ frequently exposed to sun-generated ultraviolet radiation (UVR), which is considered one of the major factors responsible for DNA damage. Such damage can be direct, through interactions of DNA with UV photons, or indirect, mainly through enhanced production of reactive oxygen species that introduce oxidative changes to the DNA. Oxidative stress and DNA damage also associate with profound changes at the cellular and molecular level involving several cell cycle and signal transduction factors responsible for DNA repair or irreversible changes linked to ageing. Crucially, some of these factors constitute part of the signalling known for the induction of biological changes in non-irradiated, neighbouring cells and defined as the bystander effect. Network interactions with a number of natural compounds, based on their known activity towards these biomarkers in the skin, reveal the capacity to inhibit both the bystander signalling and cell cycle/DNA damage molecules while increasing expression of the anti-oxidant enzymes. Based on this information, we discuss the likely polypharmacology applications of the natural compounds and next-generation screening technologies in improving the anti-oxidant and DNA repair capacities of the skin.


Individual responses of human skin to the environmental stress are determined by differences in the anatomy and physiology that are closely linked to the genetic characteristics such as pigmentation. Ethnic skin phenotypes can be distinguished based on defined genotypic traits, structural organization and compartmentalized sensitivity to distinct extrinsic aging factors. These differences are not only responsible for the variation in skin performance after exposure to damaging conditions, but can also affect the mechanisms of drug absorption, sensitization and other longer term effects. The unique characteristics of the individual skin function and, particularly, of the ethnic skin type are currently considered to shape the future of clinical and pharmacologic interventions as a basis for personalized skincare. Individual approaches to skincare render a novel and actively growing area with a range of biomedical and commercial applications within cosmetics industry. In this review, we summarize the aspects of the molecular and clinical manifestations of the environmental stress on human skin and proposed protective mechanisms that are linked to ethnic differences and pathophysiology of extrinsic skin aging. We subsequently discuss the possible applications and translation of this knowledge into personalized skincare.


The so-called active ingredients in skin care product formulations are purported to deliver the intended functions of the product. Active ingredients, such as the antioxidants can efficiently protect the skin if the activities are retained after incorporating into the base matrices in the product formulation. In this article, we investigated the antioxidant activities of 24 extracts/compounds that are being used in skin care formulations and their ability to retain the activities (efficacy) after being mixed with the base matrices. The antioxidant activities were evaluated using 2, 2’-azino-bis (3- ethylbenzothiazoline-6-sulphonic acid (ABTS) and diphenyl-picryl hydrazine (DPPH) assays. To test the efficacy of the samples in formulation, the samples were mixed with base cream 1%, 2% and 4% (w:w) and allowed to settle overnight. Results were expressed as either percentage inhibition (%) or IC50 (μg/mL). Out of the 24 samples, ten exhibited significantly high antioxidant activities with resveratrol> pomegranate> green tea> mango> amla> bearberry> ellagic acid> tetrahydrocurcuminoid> Rhodiola rosea> kakadu plum in the ABTS assay. In the DPPH assay, green tea> pomegranate> tetrahydrocurcuminoid> mango> amla> resveratrol> bearberry> Rhodiola rosea>kakudu plum>ellagic acid. Four out of the ten samples (amla, green tea, mango and pomegranate extracts) had IC50 value lower than Trolox standard and were included in the efficacy test. Trolox standard and amla extract seemed to retain their antioxidant activities in the formulations, while green tea and pomegranate extracts had a decrease in activities. Only mango extract had a synergistic effect with the cream base with higher antioxidant activity observed compared with the extract alone. This study demonstrates the potential interaction between active and vehicle compounds, which may hinder or enhance the activities of the active ingredients in the final product. The outcome of the research has an impact in the cosmetic product formulation particularly in the quality control, chemistry and efficacy of the finished products.


Human skin is a stratified endocrine organ with primary roles in protection against detrimental biochemical and biophysical factors in the environment. Environmental stress causes gradual accumulation of the macromolecular damage and clinical manifestations consistent with chronic inflammatory conditions and premature aging of the skin. Structural proteins of cell nucleus, the nuclear lamins and lamina-associated proteins, play an important role in the regulation of a number of signal transduction pathways associated with stress. The nuclear lamina proteins have been implicated in a number of degenerative disorders with frequent clinical manifestations of the skin conditions related to premature aging. Analysis of the molecular signatures in response of the skin to a range of damaging factors not only points at the likely involvement of the nuclear lamina in transmission of the signals between the environment and cell nucleus but also defines skin’s sensitivity to stress, and therefore the capacities to counteract external damage in aging.


Identifying functionally important proteins that are essential to the survival of a bacterial cell is of considerable interest in the development of new antimicrobial agents. Recent studies have shown that functionally important components in protein interaction networks may also be structurally important. We studied the protein interaction network of Bacillus subtilis to identify structurally essential proteins. Functionally essential genes encoded Fifty-four percent of the structurally essential proteins identified by our methods.