核桃壳和核桃青皮黑色素抗氧化性质的研究

Study on the antioxidant capacity of the melanin from walnut shell and walnut epicarp

为了对核桃废弃物资源进行综合利用,以核桃壳与核桃青皮为主要原料,利用氢氧化钠为提取溶剂提取黑色素,测定了核桃壳黑色素和核桃青皮黑色素的还原能力,清除·OH、O-2·、DPPH·的能力,同时分析比较了两种不同来源黑色素的红外图谱。结果表明,与人工合成的抗氧化剂BHT相比,黑色素的还原能力随浓度的升高而增大,当浓度≥0.06mg/mL时,还原能力BHT>核桃青皮黑色素>核桃壳黑色素;核桃壳黑色素和核桃青皮黑色素清除·OH的IC50值分别为0.46mg/mL和0.12mg/mL;清除O-2·的IC50值分别为0.54mg/mL和0.30mg/mL,当浓度达到0.8mg/mL时,青皮黑色素清除O-2·的能力高达94.6%,浓度为0.2mg/mL时对DPPH·的清除能力达到84.14%。红外图谱显示来自核桃壳和核桃青皮的黑色素结构相似,均可能含有酚类、胺类、醇类、芳香类等化合物。

In order to explore the comprehensive value of the discarded walnut remains,this study evaluated the antioxidant capacity of the melanin extracted from walnut shell and walnut epicarp with NaOH as extracting solvent.The total anti-oxidative activity was investigated by the reducing capacity and the scavenging activity of radicals of·OH,O-2· and DPPH· which compared with the synthetic antioxidant BHT.The structure of melanin was determined by infrared spectroscopy and compared with other studies.The results showed that melanin from walnut shell and walnut epicarp exhibited reducing capacity and played an important role in removing ·OH,O-2·,DPPH·.The reducing capacity increased with the increasing concentration.When the concentration was above 0.06mg/mL the reducing capacity of the melanin from walnut epicarp was better than that of the melanin from the walnut shell,but was weaker than BHT.The IC50 of the melanin from walnut shell scavenged the ·OH was 0.46mg/mL,while the melanin from the walnut epicarp was 0.12mg/mL.The IC50 of the melanin from walnut epicard scavenged O-2· was 0.54mg/mL,while the melanin from the walnut epicarp was 0.30mg/mL.When the concentration of the melanin from walnut epicard reached 0.8mg/mL the scavenging rate on O-2· reached to 94.6% which closes to that of VC with the same concentration,and the scavenging rate on DPPH· attained to 84.14% when the concentration was 0.2mg/mL.According to infrared spectroscopy melanin from walnut shell and walnut epicarp had similar structures containing phenolic compounds,amine compounds,alcohols,and aromatic compounds,and the anti-oxidative activity depended on the ability of providing hydrogen of the samples.