Investigating biological activities of melanin extracted from selected species of slime molds and fungi

Abstract

The major purpose of this study was to investigate the antioxidant, cytotoxicity, and antimicrobial activities of the melanin samples extracted from potential species of slime molds and fungi. The melanin pigments were extracted in an alkaline solution. Antioxidant activity, antimicrobial activity, and cytotoxicity were determined by DPPH assay, well diffusion, and SRB assays, respectively. Data on DPPH assay free radical scavenging activity suggest that melanins from three samples displayed antioxidant activities and the activities are dose-dependent. The melanin of Calvatia craniiformis possessed the highest antioxidant capacity at 1000ug/ml concentration and that’s comparable with the positive control (vitamin C). However, in terms of the antimicrobial assay, none of the samples showed notable growth inhibition activity against the pathogenic bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) at 1000ug/ml. Thus, it is concluded that at this tested concentration, melanins did not inhibit the growth of the tested bacteria. In addition, the SRB assay was performed to evaluate the cytotoxicity of the melanins toward Hep-G2 cell line. The melanin from F. septica showed an outstanding antiproliferation of Hep-G2 with the values 25.28%±4.66 of percentage cytotoxicity towards Hep-G2 cell line at the concentration of 100ug/ml. This cytotoxicity is comparable with the positive control (Camptothecin at the concentration of 0,07 ug/ml). This project generated the first data sets on the antioxidant, antimicrobial, and cytotoxicity activities of crude melanin from slime molds and fungi. The obtained results suggest that melanins have significant antioxidant activities, especially that of C. craniiformis.