| Abalone is an important aquatic economic species and its nutritional and medicinal values are recognized by the world. The processing by-products, abalone viscera, are often discarded, which cause heavy economic losses and environmental pollution. In this study, the proteoglycans from the gonad of abalone (Haliotis Discus Hannai Ino) were extracted and purified. Meanwhile, the bioactivities and the structure of the proteoglycans were investigated. The study lays the foundation for comprehensive development and utilization of the processing by-products of abalone.Abalone gonad proteoglycan (AGP) was extracted by proteolytic extraction combining alcohol extraction method and the detailed extraction method is as below. After freeze drying, the fresh abalone gonad was crushed. The powder was hydrolyzed by papain (the enzyme dose was0.2%of weight of substrate; the material to liquor ratio is1:25; the reaction temperature was45℃; the reaction pH was7.0), and the digest was boiled for1h. After centrifuging at4000r/min for10min, the supernatant was collected, mixed with three volume of50%ethanol, and stirred for1h. After conditioning for1h, the liquid was mixed with0.75volume of boiling methanol. After stirring, the mixture was stored in room temperature for24h. After centrifuging at4000r/min for10min, the supernatant was dried by rotary evaporation to get crude abalone gonad proteoglycan (CPG) with a yield of1.61%.CPG was purified to homogeneity by a combination of anion exchange chromatography and gel filtration chromatography, and the detailed separation procedure is as below. Firstly, CPG was purified by gel filtration chromatography with S-100. Secondly, the sample obtained was separated on semi-preparation high performance liquid chromatography using Source30Q column. Finally, the sample obtained was purified further by gel filtration chromatography with S-200. Through the procedure, a homogeneous proteoglycan fraction termed PGAG-2was obtained with molecular weight of10,000-13,000. It was composed of polysaccharides50.69%; proteinum2.01%; sulphate31.13%; aminohexose7.13%; aminogalactose1.33%; alduronic acid6.20%. The polysaccharide part of PGAG-2was composed of rhamnose, fucose, and galactose with molar ration of1.0:1.6:2.3. The protein part of PGAG-2contains13kind of amino acids, and high level of Glu, Gly Leu.Periodate oxidation, I.R.and NMR were used on the structure analysis of PGAG-2. The results revealed that all monosaccharide were exist as the form of pyran ring. The linkage of Fuc was1â†'2,1â†'4, and Gal was1â†'2,1â†'26,1â†'3,1â†'4,1â†'46, and Rha was1â†'3,1â†'23,1â†'24,1â†'34,1â†'234.The bioactivity evaluation experiments for CPG and PGAG-2indicated that they all have notable hydroxyl free radicals and DPPH free radicals scavenging activities, moderate reducing power and weak anti-lipid peroxidation potency. The antioxidant activities of CPG were stronger than those of PGAG-2. The reason for such phenomenon could be that the crude extracts (CPG) were rich in some low molecular weight components having higher antioxidant activity. CPG and PGAG-2all have a strong angiotensin-converting enzyme (ACE)-inhibition activity. The ACE-inhibition activity of PGAG-2were stronger than that of CPG, which indicated PGAG-2was a good ACE inhibitor. |
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