1,721,342 research outputs found
Chemical markers of pheomelanin : evaluation of their potential of predicting individual UV susceptibility
No full textRed hair, fair skin and the lack of tanning ability are generally recognized as risk factors for melanoma and other skin cancers under conditions of prolonged solar exposure. These pigmentary traits are associated with some loss of function mutations at the melanocortin-1 receptor which cause the melanocyte to produce red photosensitizing pheomelanin in preference to the default pigment, the dark eumelanin. At present evaluation of UV susceptibility relies exclusively on determination of the phenotype and phototype. Yet, not all phenotypically similar red haired individuals exhibit the same erythemogenic responses and tanning capacities, suggesting that the type and levels of pheomelanin may profoundly affect the individual response to UV radiation. Identification of specific markers of pheomelanin pigments and determination of possible relationships with skin phototypes and UV susceptibility appear therefore attractive goals. Recently we developed new procedures for analysis of pheomelanin based on identification and quantitation of specific structural markers obtained by chemical degradation of hair. The levels of these structural markers , viz.1,3-thiazole-2,4,5-tricarboxylic acid (TTCA) and 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole (BTCA) were determined in groups of red hair individuals. Whereas the majority of the red hair samples afforded TTCA in variable yields, only a restricted number of samples gave BTCA. Herein, we report new data from a larger group of red haired individuals (n=22). As a rule, the lowest MED and 5-days delayed pigmentation values were associated with BTCA-positive individuals while TTCA-positive subjects gave higher MED values (mean value 67.5 mJ cm-2, p< 0.001). Overall, these results hint at pheomelanin marker quantitation, in combination with genetic analysis and photobiogical parameters, as potential means for routine prediction of high risk individuals. A possible association of oxidative stress conditions with pheomelanic pigmentation will also be discussed
Natural polyphenols as versatile materials for applications in biomedical and food sectors : powering their potential by chemical manipulation and green methodologies
No full textIn the last decade the versatility of polyphenol chemistry and the unparalleled bioactivities exhibited by many of these compounds has increasingly been appreciated and largely translated into advanced biomedical and technological applications.
The activity of natural phenols is primarily associated to their antioxidant potential, but is ultimately expressed in a variety of biological effects. Molecular scaffold manipulation of this large class of compounds is a currently pursued approach to boost or modulate their properties. These strategies that include conjugation with biological thiols, selenylation, and polymerization will be presented [1,2] together with other examples showing how to impart biological activities to phenolic polymers, e.g. sulfation of polymers from tyrosol providing a new class of non-saccharidic heparin mimetics anticoagulants (figure, panel A ). [3]
Nowadays, the remarkable antioxidant properties have also prompted the use of natural phenolic compounds not only as food supplements, but also as additives for the development of functional materials. The presentation will be therefore focused on relevant examples of how natural phenols can be exploited as multifunctional compounds in the food, cosmetic, and biomedical sectors. Particular attention will be paid to phenolic compounds from agri-food wastes such as spent coffee grounds (figure, panel B), exhausted woods from tannin industrial production, and nut shells, which are rich in phenolic polymers including lignin and tannins, endowed with very potent antioxidant properties. [4,5] The possibility to further improve these antioxidant properties through chemical manipulation will also be presented, together with efficient and green strategies for the recovery of phenolic compounds based on the use of ball milling and/or deep eutectic solvents (DES). [6
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