PHYSICO-CHEMICAL CHARACTERISTICS AND ANTIOXIDANT PROPERTIES OF MELANINS EXTRACTED FROM LEPTOGIUM FURFURACEUM (HARM.)
Melanins are universal biopolymers, the main biological function of which is to protect living organisms from adverse factors. Interest in these dark pigments arises due to the prospects for their use in medicine, cosmeceuticals, bioremediation, bioelectronics, and other fields. In this work, a complex scheme was developed to isolate melanins from the lichen Leptogium furfuraceum (Harm.), which is a symbiotic extremophilic organism. Screening of the conditions for the extraction of melanin, its subsequent precipitation and purification made it possible to isolate three samples of melanin with a total yield of 7.5% of the dry matter of the lichen. It was established that all isolated melanins have a polyaromatic structure, they contain carbohydrates and proteins, the content of which, depending on the conditions for melanin isolation, is 7.3-9.9% and 13.5-32.7%, respectively. Among the isolated melanins, melanin, which is a water-soluble fraction of acid-precipitated melanin, displays the highest antioxidant activity. This melanin, unlike other melanins, is almost fully soluble in distilled water, 95% ethanol, 99% dimethyl sulfoxide, and phosphate buffer (pH 7.4). The differences in solubility, antioxidant activity, and chelating capacity of isolated lichen melanins make it possible to determine potential areas for their practical use.