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

Summary

Researchers optimized a method to extract melanin, a natural black pigment, from fermented wood ear mushrooms (Auricularia heimuer). Using microwave-assisted extraction with specific pH conditions, they achieved a 0.4% yield of pure melanin. The extracted melanin showed strong antioxidant properties and could be used as a natural, safe colorant and antioxidant in food and pharmaceutical products.

Background

Auricularia heimuer is the third most important cultivated mushroom in China and contains melanin, a natural pigment with antioxidant, anti-radiation, and other beneficial biological properties. Melanin from A. heimuer has potential applications as a safe and healthy colorant in medical and food industries. However, melanin extraction from A. heimuer fruiting bodies at industrial scale is difficult due to long growth cycles and high costs.

Objective

To optimize microwave-assisted extraction of melanin from A. heimuer fermentation using Box-Behnken design and response surface methodology, and to characterize the physicochemical properties and antioxidant activities of the extracted melanin.

Results

Optimal extraction conditions were alkali-soluble pH 12.3, acid precipitation pH 3.1, and microwave time 53 minutes, yielding 0.4042% AHM. AHM showed strong absorption at 210 nm, exhibited characteristic melanin absorption peaks by FT-IR, and appeared as irregular aggregates by SEM. AHM was highly soluble in alkaline conditions but insoluble in water and organic solvents, with good thermostability and light resistance.

Conclusion

Microwave-assisted extraction effectively improves melanin yield from A. heimuer fermentation. AHM demonstrates strong antioxidant activities with DPPH, OH, and ABTS free radical scavenging abilities, making it suitable for medical and food industry applications as a colorant and antioxidant.
  • Published in:Frontiers in Nutrition,
  • Study Type:Experimental Study,
  • Source: PMID: 36875843, DOI: 10.3389/fnut.2023.1131542
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