AUTHOR=Ma Yinpeng , Zhang Piqi , Dai Xiaodong , Yao Xiuge , Zhou Shuyang , Ma Qingfang , Liu Jianing , Tian Shuang , Zhu Jianan , Zhang Jiechi , Kong Xianghui , Bao Yihong 

TITLE=Extraction, physicochemical properties, and antioxidant activity of natural melanin from Auricularia heimuer fermentation

JOURNAL=Frontiers in Nutrition

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2023.1131542

DOI=10.3389/fnut.2023.1131542

ISSN=2296-861X

ABSTRACT=<sec><title>Introduction</title><p>Natural melanin from <italic>Auricularia heimuer</italic> have numerous beneficial biological properties, which were used as a safe and healthy colorant in several industries.</p></sec><sec><title>Methods</title><p>In this study, single-factor experiments, Box-Behnken design (BBD), and response surface methodology (RSM) were employed to investigate the effects of alkali-soluble pH, acid precipitation pH, and microwave time on the extraction yield of <italic>Auricularia heimuer</italic> melanin (AHM) from fermentation. Ultraviolet-visible spectrum (UV-Vis), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and high-performance liquid chromatography (HPLC) were used to analyze the extracted AHM. The solubility, stability, and antioxidant activities of AHM were also measured.</p></sec><sec><title>Results</title><p>The results showed that alkali-soluble pH, acid precipitation pH, and microwave time significantly affected the AHM yield, with the following optimized microwave-assisted extraction conditions: alkali-soluble pH of 12.3, acid precipitation pH of 3.1, and microwave time of 53 min, resulting in an AHM extraction yield of 0.4042%. AHM exhibited a strong absorption at 210 nm, similar to melanin from other sources. FT-IR spectroscopy also revealed that AHM exhibited the three characteristic absorption peaks of natural melanin. The HPLC chromatogram profile of AHM showed a single symmetrical elution peak with a 2.435 min retention time. AHM was highly soluble in alkali solution, insoluble in distilled water and organic solvents, and demonstrated strong DPPH, OH, and ABTS free radical scavenging activities.</p></sec><sec><title>Discussion</title><p>This study provides technical support to optimize AHM extraction for use in the medical and food industries.</p></sec>