Isolation and characterization of biologically active melanin from Actinoalloteichus sp. MA-32
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The DPPH (2,2-diphenyl-1-picrylhydrazyl) assay has been widely used in antioxidant evaluation. However, it suffers from certain limitations that are addressed in this contribution. The limitations discussed in this work were the ratio of DPPH radicals to antioxidants and the presence of pigments in the reaction medium which interferes with absorbance readings. To do so, we used eight different concentrations of DPPH solution. The modified DPPH assay proposes a new concept, IC100, that is defined as the amount of DPPH radical required to oxidize all antioxidants present in the reaction medium. The modified DPPH assay does not suffer from an underestimation of antioxidant activity found in the original DPPH procedure due to the decrease in the ratio of DPPH radicals to antioxidants. Moreover, the modified method was not influenced by interference from coexisting pigments in the measurement of radical scavenging potential of extracts. To the best of our knowledge, this is the first attempt to effectively resolve the above-mentioned limitations of the DPPH assay.
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4 Abstract: Artimisia scoparia is extensively used as a natural therapeutic agent in the treatment of various diseases. The current study was designed to explore antioxidant potential of extract/fractions in DPPH free radical and reducing power assays. The results suggested marked antioxidant potential of extract/fractions in both DPPH and reducing power assays. Of the test articles, ethyl acetate was the most dominant fraction in both assays followed by crude methanolic extract. In conclusion, A. scoparia illustrated an outstanding antioxidant activity.
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Melanin has a photo-screening, a biophysical/biochemical and a cosmetic effect. Melanin content of cultured pigmented cells can be measured by spectrophotometry and expressed either as melanin content per cell or melanin content per culture (area). Melanin production can be calculated from melanin content and cell number at the beginning and at the end of a culture using various formulas and expressed as melanin production per cell per day or melanin production per culture per day. Melanin content or production per cell have been used widely to compare melanin content in various cell lines or to compare the melanin content during different stages in the culture (e.g. growing stage and senescent stage). For the evaluation of changes in melanin content and production in a given pigment cell line after treatment with a special chemical, physical or biological stimulator or inhibitor, different parameters used for the evaluation of experimental data can lead to conflicting results. Melanin content per area is determined by melanin content per cell and the number of cells in this area. The biological and cosmetic effects of melanin in vivo are determined mainly by melanin content per area, not melanin content per cell. For example, if melanin content per cell is the same, but the number of cells in a given area is increased after the treatment, then the melanin content per area is also increased. Under this circumstance, the color of skin turns darker and the total antioxidant activity provided by melanin in this area is increased even though the melanin content per cell measured remains the same; therefore, melanin content or production per culture is more important than melanin content or production per cell under this circumstance.
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Abstract Melanin is a major virulence factor in pathogenic fungi that enhances the ability of fungal cells to resist immune clearance. Cryptococcus neoformans is an important human pathogenic fungus that synthesizes melanin from exogenous tissue catecholamine precursors during infection, but the type of melanin made in cryptococcal meningoencephalitis is unknown. We analyzed the efficacy of various catecholamines found in brain tissue in supporting melanization using animal brain tissue and synthetic catecholamine mixtures reflecting brain tissue proportions. Solid-state NMR spectra of the melanin pigment produced from such mixtures yielded more melanin than expected if only the preferred constituent dopamine had been incorporated, suggesting uptake of additional catecholamines. Probing the biosynthesis of melanin using radiolabeled catecholamines revealed that C. neoformans melanization simultaneously incorporated more than one catecholamine, implying that the pigment was polytypic in nature. Nonetheless, melanin derived from individual or mixed catecholamines had comparable ability to protect C. neoformans against ultraviolet light and oxidants. Our results indicate that melanin produced during infection differs depending on the catecholamine composition of tissue and that melanin pigment synthesized in vivo is likely to accrue from the polymerization of a mixture of precursors. From a practical standpoint our results strongly suggest that using dopamine as a polymerization precursor is capable of producing melanin pigment comparable to that produced during infection. On a more fundamental level our findings uncover additional structural complexity for natural cryptococcal melanin by demonstrating that pigment produced during human infection is likely to be composed of polymerized moieties derived from chemically different precursors.
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This study was carried out to investigate the antioxidant effects of melanin extracts, including silkie fowl skin melanin (SS-melanin), silkie fowl comb melanin (SC-melanin), sepia ink sac melanin (SE-melanin), octopus ink sac melanin (OC-melanin) and synthetic melanin (SY-melanin).The results showed that with the addition of melanin extracts, linoleic acid peroxide significantly, decreased (p<0.05) with the increase in the irradiative time of UV and that OC-melanin had the highest efficiency on antioxidant activity (p<0.05).Melanin extract had reducing power and chelating power to Fe 2+ , which increased with the increase in the different melanin concentration.Therefore, it could be concluded that the antioxidant action of melanin extracts did not come from one single function, but is a result of many characteristic functions.(
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Antioxidant activity of the crude methanol extract of Pseudarthria viscida (L) Wight and Arn. stem and root was performed by1,1-diphenyl-2-picrylhydrozyl (DPPH) radical quenching assay and reducing power test models. Both stem and root extracts exhibited potential antioxidant activity in both the assays.
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The purpose of the study was to establish an in vitro model for the quantification of the melanin produced in human melanocytes in culture. Melanin content in these cultured human melanocytes is determined by spectrofluorimetric assay. Fluorescence intensity is quantitatively related to the melanin content present in cultured melanocytes.
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Melanin is a major virulence factor in pathogenic fungi that enhances the ability of fungal cells to resist immune clearance. Cryptococcus neoformans is an important human pathogenic fungus that synthesizes melanin from exogenous tissue catecholamine precursors during infection, but the type of melanin made in cryptococcal meningoencephalitis is unknown. We analyzed the efficacy of various catecholamines found in brain tissue in supporting melanization using animal brain tissue and synthetic catecholamine mixtures reflecting brain tissue proportions. Solid-state NMR spectra of the melanin pigment produced from such mixtures yielded more melanin than expected if only the preferred constituent dopamine had been incorporated, suggesting uptake of additional catecholamines. Probing the biosynthesis of melanin using radiolabeled catecholamines revealed that C. neoformans melanization simultaneously incorporated more than one catecholamine, implying that the pigment was polytypic in nature. Nonetheless, melanin derived from individual or mixed catecholamines had comparable ability to protect C. neoformans against ultraviolet light and oxidants. Our results indicate that melanin produced during infection differs depending on the catecholamine composition of tissue and that melanin pigment synthesized in vivo is likely to accrue from the polymerization of a mixture of precursors. From a practical standpoint, our results strongly suggest that using dopamine as a polymerization precursor is capable of producing melanin pigment comparable to that produced during infection. On a more fundamental level, our findings uncover additional structural complexity for natural cryptococcal melanin by demonstrating that pigment produced during human infection is likely to be composed of polymerized moieties derived from chemically different precursors.
Neuromelanin
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Virulence factor
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Background: Antioxidants are substances that can reduce free radicals to protect the body's biological systems from adverse effects arising from processes or reactions that cause excess oxidants. Kedondong leaves (Spondias dulcis Forst.) contain flavonoids, tannins, and alkaloids, which have the potential to act as antioxidants. Objective: To determine the antioxidant activity of ethyl acetate and 95% ethanol extracts from kedondong leaves. Methods: The antioxidant activity was tested using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method, a free radical stable in an aqueous solution. Each extract was tested for its antioxidant activity with a comparison compound, vitamin C, using a UV-Vis spectrophotometer. The results of the antioxidant activity test revealed the IC50 (inhibitory concentration) value, namely the concentration of antioxidant compounds capable of inhibiting DPPH free radical activity by 50%. Result: The ethyl acetate extract has weak antioxidant activity with an IC50 value of 194.123 ppm, the 95% ethanol extract has very weak antioxidant activity with an IC50 value of 553.3694 ppm, and vitamin C, as a comparison, has very strong antioxidant activity with an IC50 value of 4.7805 ppm. Conclusion: Kedondong leaves have potential antioxidant activity but are very small.
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