Components And Antioxidant Activity Of Hot Water Extracts From Abalone Muscle

Abalone,which is one of the important economic shellfish in China,has delicious taste,rich nutrients and certain physiological activities.In daily diet,abalone is often cooked by boiling and stewing,during which some of the nutrients from muscle dissolve into the hot water.In order to explore the nutrition and functional activities of the dissolved components from abalone muscle during cooking,hot water extracts were obtained using hot water leaching abalone muscle in this study.The physical and chemical properties of hot water extract were studied.And the antioxidant activities of the digested product of hot water extracts were explored.Finally,the change of antioxidant components activity from hot water extract during transport were investigated.Firstly,the boiling water extracts(BWE)was obtained from abalone muscle by boiling water at different time sections,and the effect of extracting time on component of BWE from abalone muscle was investigated.Based on the result of SDS-PAGE analysis,it was found that the BWE extracted for 1 min mainly contained proteins with molecular weight(MW)of 65 kDa and 220 kDa.With further increasing the extraction time,the protein of 65 kDa MW became dominant in the BWE.The periodic acid-schiff(PAS)staining indicated that the protein band of 65 kDa MW was glycoprotein,suggesting that glycoprotein from abalone muscle was easily dissolved in the boiling water during extraction.The umami and sweet amino acids including Glu,Asp,Gly and Ala were the major amino acids of BWE,while the ratio of arginine/lysine was gradually increased with increasing extraction time.The monosaccharide analysis indicated that the polysaccharides from abalone muscle during extraction were mainly composed of glucose,and the mole ratio of glucose in the polysaccharides was increased from 85.30%to 98.27%.The results of ash and mineral contents showed that the elements of Na and Zn in the abalone muscle were more soluble into the boiling water than the other elements.It can be concluded from above results that the extracting time of boiling water will affect the nutritional composition of BWE,and the loss of nutritional constituent in the abalone processing can be reduced by controlling the immersed time.Nextly,the physicochemical properties of pressurized hot-water extract(PHE)from abalone muscle and the antioxidant activities of its digestive products were investigated.The PHE contained protein of 46.35%and carbohydrate of 39.22%.After ethanol graded precipitation,most of carbohydrate and protein in PHE were successively remained in 40%ethanol precipitate(EP40)and 80%ethanol precipitate(EP80),respectively.High proportions of Glu and Gly were found in the PHE,EP40 and EP80,but the proportion of Ala in ethanol soluble extract(ESE)reached up to 46.00%.Both PHE and EP40 were rich in glucose,while galactose and glucose were main monosaccharides in the EP80 and ESE.Based on the results of SDS-PAGE and HPLC,high molecular weight components from PHE were precipitated in the EP40,but oligopeptides and free amino acids were fractionated in EP80 and ESE.Among the PHE and the digestive products,the highest antioxidant ability was found to be EP80 hydrolysate,the IC50 values of which for scavenging activity on hydroxyl radical,DMPD radical and ABTS radical were 1.05 mg/mL,1.40 mg/mL and 0.56 mg/mL,respectively.It is concluded that carbohydrate of abalone muscle was dissolved more easily into hot water than protein,and protein hydrolysate of PHE might play an important role in antioxidant activity of gastrointestinal digestion.Finally,in order to further explore the antioxidant activity of hot water extracts from abalone muscle after absorption,the transport components were analyzed using the Caco-2 cell transport model.The EP80 hydrolysate was separated by Sephadex G-15 to obtain three components of F1,F2 and F3.Among them,the molecular weight of F2 mainly distributed in around 350 Da.The IC50 values of hydroxyl radical and ABTS radical scavenging activity of F2 were lower than F1 and F3,which were 0.763 mg/mL and 0.028 mg/mL,respectively.Caco-2 cells formed a tightly cell monolayer after culture 21 days.The TEER value of the cell monolayer reached 308 Ω·cm2,and the alkaline phosphatase activity ratio of AP/BL reached 2.23.The cell transport model was established.After transported F2 through the Caco-2 cell transport model,it was found that the BL-side transport component showed higher antioxidant activity and was speculated to contain Leu-Tyr,Gly-Ala-Ala,His-Gly-Ser-Ala by mass spectrometry analysis.This indicated that the F2 could exert higher antioxidant activity after being absorbed through the small intestine.In conclusion,the hot water extract obtained from the abalone muscle contained rich nutrients and has strong antioxidant activities.Antioxidant components in hot water extracts can be transported and absorbed through intestinal epithelial cells to exert better antioxidant effects.