柱状田头菇黑色素的分离、鉴定及其稳定性和抗氧化活性

为了解柱状田头菇(Agrocybe aegerita)子实体色素类别和性能,对柱状田头菇子实体中色素进行了提取、纯化和鉴定并对其稳定性和抗氧化活性进行研究。结果表明:柱状田头菇色素易溶于碱性溶液,微溶于水,不溶于有机溶剂;紫外光区212nm处有最大吸收峰,傅利叶红外光谱图与酪氨酸合成黑色素相似,初步鉴定柱状田头菇色素属于3,4-二羟基苯丙氨酸类黑色素;pH11~14,20~100℃范围内,黑暗条件下柱状田头菇黑色素稳定性较好,在自然光条件下稳定性最差,其次是紫外光;柱状田头菇黑色素具有一定的还原能力、DPPH·清除能力及Fe2+螯合能力。

Extraction,Characterization, Stability and Antioxidative Capacity of Agrocybe aegerita Melanin

A melanin-like pigment was extracted from Agrocybe aegerita by suspending 10 g powdered fruit bodies in 300 mL 1.0 mol/L NaOH,for 20 min at 60 ℃ while subjecting to ultrasound (80 W).After centrifugation (2400 g,20 min),the supernatant was adjusted to pH 1.5 using 2.0 mol/L HC1,incubated at 80 ℃ for 12 h,the precipitated material collected by centrifugation (2400 g,20 min) and washed three times with dd H2O and freeze-dried.Crude pigment was purified by suspending one gram in 150 mL 2.0 mol/LHCl,heating at 100 ℃C for 2 h,collecting the precipitated material by filtration,re-suspending in 100 mL ddH2O and solubilizing by adjusting the pH to 10 with 1.0 mol/L NaOH.The solution was mixed with 20 mL chloroform:n-butanol (4:1),incubated for 30 min at room temperature,centrifuged (15000 g,15 min) to separate and remove the organic layer,and the pH adjusted to 1.5 using 2.0 mol/L HC1.Precipitated material was collected by centrifugation (15000 g,15 min),washed three times with dd H2 O,and resuspended in 5.0 mL dd H2O.Ethyl acetate (5.0 mL) was added,the aqueous phase was separated and removed by centrifugation (24000 g,10 min),after which the organic phase was washed three times with dd H2O and freeze-dried to obtain pure pigment.A.aegerita pigment was soluble in alkaline solution,slightly soluble in water and insoluble in 1 mol/L HC1,95％ ethanol,ethyl acetate and chloroform.It was stable at temperatures between 20-100 ℃,pH values between 11 and 14,but was unstable when exposed to natural and UV light.UV-Vis and Fourier transform infrared spectroscopy showed the pigment had a structure similar to synthetic tyrosine melanin,and belonged to the group of 3,4-dihydroxyphenylalanine melanins.