超声降解法制备可溶性鱿鱼墨黑色素及其抗氧化性

Ultrasound-assisted degradation for preparing soluble melanin from squid ink and its anti-oxidant activity

实验研究了一种在碱性条件下利用超声降解制备可溶性鱿鱼墨黑色素的新方法。将鱿鱼墨黑色素溶于NaOH后用超声细胞破碎仪处理1 h,超滤后分别获得不同分子量可溶性黑色素组分。结果显示,超声处理后黑色素平均粒度从17.34μm下降至1.467μm,紫外、红外光谱和核磁共振谱图从结构上说明超声作用主要破坏黑色素的高度聚合状态,而黑色素的主要化学结构并没有被破坏,只有少部分基团,尤其是较低分子量组分中的DHI和DHICA结构被氧化;体外抗氧化实验显示经过0.5 mol/L和1 mol/L的NaOH处理,分子量大于10 ku的组分具有很强的抗氧化性,这些组分清除超氧自由基能力(IC50=19～80μg/mL)远优于作为商品抗氧化剂的肌肽(IC50=355μg/mL);清除羟基自由基活性(IC50=115～180μg/mL)与肌肽(IC50=110μg/mL)相当。可溶性鱿鱼墨黑色素作为一种天然色素和新型自由基清除剂,其良好的可溶性大大提高了机体的吸收利用率。

We developed a new method using ultrasound-assisted degradation under alkaline condition for preparation of solution squid ink melanin. The squid ink melanin was mixed with NaOH solvent in brown glass tubes. The melanin-solvent suspension was treated by ultrasound for 1 h and then divided into three different molecular weight（Mw） fractions by membrane separation（below 10 ku, among 10 -50 ku and over 50 ku）. The result showed that the mean diameter of the squid ink melanin was decreased from 17.34 μm. to 1. 467 μm after ultrasound process. UV,IR and solid13C NMR spectra indicated that the basic structure of melanin fraction was still retained after ultrasound process. The fraction with Mw below 10 ku showed more severe degree of oxidation on active groups （DHI and DHICA） than those above 10 ku. Further in vitro analysis showed soluble melanin fractions obtained in 0.5 and 1 mol/L NaOH, with Mw above 10 ku which had greater characteristic absorption peak of - OH and - NH structure exhibited much higher antioxidant potency. The IC50 of these fractions（ among 19 -80 μg）on scavenging 02- · is more efficient than carnosine （IC50 = 355 μg/mL. ）, a commercialized antioxidant. And they （ IC50 among 115 - 180 μg/mL） are as efficient as carnosine（ICs0 = 110 μg/mL）on scavenging · OH in free radical scavenge assay. In conclusion, our results showed that soluble squid melanin is a natural pigment and a new free radical scavenger with a promising prospect. The excellent solubility can increase absorption and enhance utilization rate in vivo, providing a potential prospect for squid ink melanin product as a natural antioxidant.