Based on the single factor experiment, Box-Behnken experiment was designed to obtain the optimum extraction conditions of Lachnum YM-346 melanin (LM346): NaOH 1.00 µg·mL-1, ultrasonic time 58.02 min and ultrasonic temperature 64.61°C. Under these conditions, the yield of melanin was 3.19 % higher than that by alkali extraction and acid precipitation. Infrared spectroscopy showed that LM346 had characteristic absorption peaks at 1654.213 cm-1 and 3324.19 cm-1 , which represented the C=O and O-H stretching vibration of indole ring, 1HNMR revealed that LM346 had absorption peaks at 7.0-7.5 ppm and 2.5-5.0 ppm as a result of indole CH=C and NH, and pyrolysis/GC/MS indicated that there were a large amount of pyrrole, benzene and their derivatives in the pyrolysis products, suggesting that LM346 was an indole type melanin. The antibacterial activity of this melanin against the test bacteria was higher than that of tetracycline.
Melanin from Lachnum; Box-Behnken design; Ultrasonic-assisted extraction; Indole-type; Antibacterial activity
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