Antioxidant Activity of the Melanin Pigment Extracted from Aspergillus nidulans

Abstract

Melanins are black or brown pigments of high molecular weight formed by oxidative polymerization of phenolic or indolic compounds. They are found in organisms of all phylogenetic kingdoms, showing a broad spectrum of biological roles, including thermoregulation, chemoprotection, camouflage and sexual display. 1) These pigments are not essential for fungal growth and development, but have been reported to act as "fungal armor" because of the ability of the polymer to protect these microorganisms against harmful environmental conditions such as UV radiation, temperature extremes, hydrolytic enzymes, metals or plant defense mechanisms. [2][3][4][5][6][7] The effect of melanin enhancing the survival of fungi can be mainly due to its function as an extracellular redox buffer which can neutralize oxidants generated by environmental stress. 8) Wang and Casadevall 9) observed that melanized Cryptococcus neoformans cells survived the action of nitrogen-and oxygen-derived oxidants approximately 10-fold better than did non-melanized cells, suggesting that melanin contributes to virulence by protecting pathogens against free radicals generated immunologically. Studies on oxidative damage have shown that melanin in Wangiella dermatidis and Alternaria alternata appeared to confer cellular redox properties similar to those conferred by melanin upon C. neoformans. 10,11) Hoogduijn et al. 12) observed that melanin protects melanocytes and keratinocytes from the induction of DNA strand breaks by hydrogen peroxide, indicating that this pigment has an important antioxidant role in the skin.In the last decades, skin cancer has been increasing alarmingly due to chronic exposure to UV light and certain environmental chemicals. The major cause of DNA damage induced by these agents is the production of reactive oxygen species (ROS) and free radicals. 13,14) Substances acting as antioxidants, i.e., reactive oxygen and radical scavengers, protect cells from ROS-mediated DNA damage, which can result in mutation and subsequent carcinogenesis. 15,16) Various studies have demonstrated that melanins act as antioxidants and suggest its use as a raw cosmetic material to minimize light-and toxin-induced tissue destruction. 1,17) In this context, fungal melanin is of considerable biotechnological interest because it can be produced for low cost on a large scale compared with industrially-produced melanin, making its use as an antioxidative agent in cosmetic formulations economically advantageous. Taking this information into account, in the present study we assessed the antioxidant activity of the melanin pigment extracted from A. nidulans fungus in order to determine its possible utilization in the pharmaceutical industry. RESULTS AND DISCUSSIONWe first assessed the antioxidant activity of synthetic melanin, which was used as a control in the study because of its recognized activity as a reactive oxygen species (ROS) scavenger 5) As shown in Tables 1 and 2, the oxidation of 5-thio-2-nitrobenzoic acid (TNB) by hydrogen peroxide (H 2 O 2 ) and h...

Production of Melanin Pigment by Fungi and Its Biotechnological Applications

“…It has been reported that melanin protects melanocytes and keratinocytes from the induction of DNA strand broken by hydrogen peroxide, indicating that this pigment also has an important antioxidant role in the skin [107]. Studies in our laboratory showed that melanin extracted from hyperpigmentproductive mutant (MEL1) of A. nidulans has the ability to scavenge the biological oxidants, as HOCl, and may be a promising material in cosmetic formulations to protect the skin against possible oxidative damage [31].…”

“…Studies have shown that the effect of melanin enhancing the survival of fungi under adverse conditions can be mainly due to its powerful free radical scavenger properties, acting as a "sponge" for other free radicals generated by the fungus in response to environmental stress [20,29,30]. Apart from this scavenging ability, melanin exhibits other biological activities, including thermoregulatory, photoprotective, antimicrobial, antiviral, cytotoxic, anti-inflammatory, radioprotective, and immunomodulatory [13,17,18,[31][32][33][34].…”

Physicochemical characteristics and antioxidant activity of melanoidin pigment from the fermented leaves of Orthosiphon stamineus

“…The reduced activity of AEOS was probably caused by the presence of other accompanying components of the O. stamineus extracts. Analogous parameters determined previously for synthetic melanoidin and melanoidin from Aspergillus nidulans were significantly lower -57.91 and 186.17 μg/mL, respectively (Goncalves & Pombeiro-Sponchiado, 2005). OS-M can therefore be considered a good H 2 O 2 inactivator.…”

Evaluation of the Practicality of Melanin as a Photodynamic-Inactivation Photosensitizer by Its Nanonization

“…It is shown that Sepia melanin can be nanonized and dispersed in pure water or biological medium by processing of melanin powder in suspension with a magnetic stirrer running for 48 h. It is also shown that irradiation of Sepia melanin in suspension with femtosecond laser pulses can result in photo-fragmentation, which leads to nanonization and dispersibilization at a rate higher than that with mechanical stir. In this report and our previous work [9] we have demonstrated that both Sepia melanin (natural melanin) and synthetic melanin can be nanonized and dispersed in pure water or biological medium by processing of melanin powder in suspension with a magnetic stirrer running for 48 h. Although water-dispersible melanin processed with the techniques reported herein would not be practical photosensitizer for PDI, we expect it could be utilized in other applications such as adjuvant in radiation therapy [38], antioxidant [4,5,9,39], metal-ion scavenger [40], antidote for acute radiation syndrome [38], antitumor drug [41,42], antivenin drug [43], antivirus [44] and contrast-enhancing agent in magnetic resonance imaging (MRI) [45,46].…”

“…Melanocytes in the human epidermis have numerous enzymes with capabilities in antimicrobial defense and functional links to the immune system, in which melanin may play an activating role [1][2][3]. In addition, some researches revealed that melanocytes play a key role in protecting our skin from damaging effects of solar UV radiation by scavenging free radicals and reactive oxygen species (ROS), besides simply attenuating the radiation [4,5]. On the other hand, it has been found that melanin has great potential in many industrial and medical applications [6][7][8].…”