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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Tyrosine is the precursor of melanin and the synthetic reaction sequence is as follows: dopa, dopaquinone, leukodopachrome, dopachrome, 5,6-dihydroxyindole, indole-5,6-quinone, and melanin. In the Raper-Mason scheme of melanin synthesis, the enzyme tyrosinase oxidizes tyrosine to dopa and also catalyzes the formation of dopaquinone.98 This reaction occurs within the melanocyte. In albinism, there is a genetic defect (absence of tyrosinase) which prevents the oxidation of dopa.99,100
Basic Science
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
In 1980, Pawelek reported tyrosinase-related protein1 (TYRP1) and DOPAchrome tautomerase (DCT) produced in melanocytes, which prevented spontaneous decarboxylation of Dopachrome to DHI and led to production of more soluble and lighter colored carboxylated melanin, known as DHICA melanin [1].
Hair Coloring
Published in Dale H. Johnson, Hair and Hair Care, 2018
The initial theory of eumelanin biosynthesis comes from the works of Raper (1) and Mason (2), who postulated that the amino acid tyrosine [1] was converted to eumelanin through a number of stages some of which were controlled en-zymically. In general terms, as shown in Figures 1 and 2, tyrosine [1] is first hydroxylated to 3,4-dihydroxyphenylalanine (DOPA) [2]. Oxidation to dopaquinone [3], followed by cyclization to leucodopachrome (cyclodopa) [4] and further oxidation, gives dopachrome [5]. Decarboxylation of dopachrome gives 5,6-dihydroxyindole [6]. Oxidation of [6] gives the quinone [7], which then polymerizes to melanin presumably through a number of oligomeric stages. The enzyme tyrosinase is an important catalyst in some of these steps.
Antibacterial, Antioxidant and Melanogenesis Inhibitory Activity of Auraptene, a Coumarin from Ferula szowitsiana Root
Published in Nutrition and Cancer, 2022
Ensiyeh Charmforoshan, Ehsan Karimi, Ehsan Oskoueian, Mehrdad Iranshahi
Due to the investigation of anti-tyrosinase properties murine melanoma B16F10 cell line (ATCC CRL-6475) were cultured and grown in a 6-well plate with a density of 5 × 104 cells/ml. Then, the media was removed after 24 h, and serial concentration of auraptene and kojic acid were replaced. The cells were incubated for 72 h and the viability of the cells was determined by using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT). The cells incubated in culture media devoid of auraptene (0 µg/ml) were considered as a negative control. The melanin content of the cells was performed base on Sun et al. (18) assay. Briefly, the cultivated cell was harvested after 72 h, of incubation and washed two times with phosphate-buffered saline. Eventually, the cells were lysed, heated for one hour (80 °C) and the melanin content was read at a wavelength of 400 nm. The expression of melanin biosynthesis-related genes namely Tyrosinase (TYR), tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2/DOPAchrome tautomerase (TRP-2) in the B16F10 cells was determined using real-time PCR (19).
Screening the dermatological potential of Plectranthus species components: antioxidant and inhibitory capacities over elastase, collagenase and tyrosinase
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Joana M. Andrade, Eva María Domínguez-Martín, Marisa Nicolai, Célia Faustino, Luís Monteiro Rodrigues, Patrícia Rijo
The isolated compounds (Figure 2) and extracts (both organic and aqueous) from the described Plectranthus plants were tested in the anti-tyrosinase activity assay with modifications15. The assay was performed using 180 L of the substrate L-tyrosine (0.5 mM) in PBS 50 mM (pH 6.8) and 10 L of the tested samples (50 g/mL) incubated for 5 min at 37 C before starting the reaction by adding 10 L of tyrosinase (5000 U). After incubation at 37 C for 5 min, production of dopachrome was detected from absorbance measurements at 450 nm every 2 min, for 10 min, in a microplate reader (Thermo-Fisher Scientific). Kojic acid (0.8 mM) was used as positive control, with reported IC50 of 43.7 M49, and sample solvent (DMSO 0.5% (v/v) in PBS buffer) as negative control. All assays were performed in triplicate. Results were expressed as percentage inhibition (%) determined from Equations (2) and (3). The absorbance variation (Abs) registered by Equation (2) for enzyme velocity reaction of negative control (Abs/time) must be in the linear range.
Collagen biosynthesis stimulation and anti-melanogenesis of bambara groundnut (Vigna subterranea) extracts
Published in Pharmaceutical Biology, 2020
Romchat Chutoprapat, Waraporn Malilas, Rattikarl Rakkaew, Sarinporn Udompong, Korawinwich Boonpisuttinant
The tyrosinase inhibition activity of the BG extracts was performed by the modified dopachrome method using tyrosine as a substrate as previously described (Boonpisuttinant et al. 2014). Briefly, 50 µL of the samples at various concentrations, 50 µL of 0.1 mg/mL L-tyrosine, 50 µL of 0.1 mg/mL mushroom tyrosinase and 50 µL of 0.1 mM phosphate buffer were added in 96-well microplates. Kojic acid was used as a standard. The mixture was incubated at 37 °C for 60 min. Before and after incubations, the absorbances were measured at 450 nm by a microplate reader. The percentages of tyrosinase inhibition were calculated according to the following equation: 50) were calculated from the graph plotted between % inhibition activity and the concentrations.