Identification and antioxidant activity of melanin isolated from Hypoxylon archeri, a companion fungus of Tremella fuciformis

Abstract

Melanin produced by Hypoxylon archeri, a companion fungus of Tremella fuciformis, was purified from the submerged culture medium and designated as HM. Ultraviolet-visible and FTIR spectra of the purified HM showed significant similarities with those of the synthesized melanin derived from tyrosine. Thus, the HM melanin was identified to be derived from the precursor molecule of tyrosine or dihydroxyphenylalanine (DOPA). The antioxidant activity of HM melanin, synthetic melanin and vitamin C were compared by inhibition of the oxidation of 5-thio-2-nitrobenzoic acid (TNB) caused by hypochlorous acid (HOCl) and hydrogen peroxide (H(2)O(2)). The HM melanin is likely to be more efficient eliminating oxygen free radicals generated by H(2)O(2) than by HOCl. At a concentration of 100 mg x l(-1), the HM melanin protected 80.95% of TNB oxidation by H(2)O(2), slightly higher than the synthetic melanin. Inhibition curves as a function of time also revealed the HM melanin was a more efficient inhibitor of H(2)O(2) oxidation with an average TNB (TNB(acr)) consumption rate of 0.0553 mmol l(-1 ) x min(-1 )during the inhibition phase. Therefore, HM melanin is an efficient scavenger of peroxide free radicals.

Sunlight Exposure–Mediated DNA Damage in Young Adults

“…One is via the antioxidative effect and the other is via physical block of sunlight (26,27). There was no significant correlation between urinary 8-OHdG levels and constitutive cutaneous melanin density (L*-values of the sole) in the subjects.…”

Chemical composition and radical scavenging activity of melanin from Auricularia auricula fruiting bodies

“…Purification of melanin was performed as described by Wu et al (2008) with proper modification. Melanin extract was first adjusted to pH 2.0 with 3 M HCl to precipitate melanin, followed by centrifugation at 10000 rpm for 20 min and the pellet was collected.…”

“…In recent studies (Liu et al, 2005;Tu et al, 2009), protein is considered to be an important component in melanins and can affect the function of the assembled pigment. Melanins from different sources possess a number of healthful functions, such as antioxidation (Tu et al, 2009;Wu et al, 2008), anti-HIV activity (Manning et al, 2003;Montefiori & Zhou, 1991), and immunomodulatory activity (Sava et al, 2001). These functions promise natural melanin with great development potential as a healthful food colorant.…”

Properties of melanin from black tea leaves

“…After that the sample was centrifuged at 2100g for 5 min and the supernatant containing melanin was obtained and stored at 4°C in the dark. Purification of melanin was performed as described by Wu et al 5 with modification. Melanin extract was first adjusted to pH 2.0 with 3 M HCl to precipitate www.scienceasia.org melanin, followed by centrifugation at 13 000g for 20 min and the pellet was collected.…”

“…Melanin is a high molecular weight pigment (generally of red, black, or brown colour) produced from oxidative polymerization of phenolic or indolic compounds 1 . Melanin from natural sources, such as black-bone silky fowl 2 , Osmanthus fragrans seeds 3 , Auricularia auricula fruit-bodies 4 , and Hypoxylon archeri 5 of microorganisms possess similar physicochemical properties. These physicochemical properties include strong light absorbance, unusual solubility, and remarkable redox properties.…”