| Hypsizygus marmoreus,a kind of edible fungus with rich nutrition values,exhibits various biological activities,such as anti-aging,anti-cancer,anti-oxidant,fatigue resistance,reducing blood fat,strengthening the body immunity,and so on,and thus possesses great value for exploitation and utilization.Oxidation will not only make oil metamorphism in the food,but also can make food fading discoloration and destructing of vitamins,and thus resulting in a decrease of the sensory quality and nutritional value of the food,and even production of toxic substances which would lead to food poisoning.Food antioxidant can prevent or delay the oxidation of food and improve the stability of food and prolong the food storage period.Food antioxidants,according to their sources,can be classified into two catalogs:natural antioxidants and chemical synthesis antioxidants such as BHA and BHT.Chemical synthesis antioxidants have been limited to be used as food antioxidant,due to their potential toxicity.Hence,to exploit natural antioxidant used in the food industry has attracted increasing attention.In this study,two new varieties,consisting of MinZhen No.2 and MinZhen No.3,were used as experimental materials.MinZhen No.2,one new H.marmoreus high yielding variety,was generated by fusing the protoplasts of H.marmoreus and Pleurotus sajor-caju,and subsequently screened out on the basis of laccase secretion capability.While,MinZhen No.3,another new H.marmoreus variety with excellent production characteristics,was bred by the combination of molecular marker technique and protoplast monokaryon strategy.At present,these two new varieties used as industrial production strains for large-scale production of mushroom have been achieved.In this study,the antioxidant activities of polyphenols and polysaccharides extracted from MinZhen No.2 and MinZhen No.3 were analyzed.Our results will provide a theoretical basis and technical support for exploiting natural antioxidant originated from H.marmoreus,and preliminarily determine the aromas of H.marmoreus.The main conclusions obtained from this study are as follows:1.Study on extraction and antioxidant activities of water solvable polyphenols from two H.marmoreus strainsThe optimal extraction conditions for polyphenols from MinZhen No.2 were pure water,liquid to material ratio 28:1(mL/g),extraction time 4 h,and extraction temperature 43 ℃.While the optimal extraction conditions for polyphenols from MinZhen NO.3 were pure water,liquid to material ratio 35:1(mL/g),extraction time 3.5 h and extraction temperature 43 ℃.According to the optimal extraction conditions,actual extraction yield of polyphenols extracted from MinZhen No.2 and MinZhen No.3 was 6.08 ± 0.03 and 3.42 ± 0.03 mg/g,respectively.Under the optimal polyphenol extract conditions,the extracted polyphenol content of MinZhen No.2 was 1.78-fold the amount of that of MinZhen No.3.Furthermore,total antioxidant activities and DPPH free radical scavenging activities for polyphenol extracts from MinZhen NO.2 and MinZhen No.3 were comparable.However,polyphenol extracts from MinZhen NO.2 exhibited higher ABTS free radical scavenging activities than that of MinZhen NO.3.In addition,when compared to positive control Vitamin C,polyphenol extracts from both H.marmoreus strains displayed lower antioxidant activities.2.Study on the antioxidant activities of various solvent extracts from two H.marmoreus strainsAntioxidant activities of various solvent extracts were analyzed and their polyphenol contents were determined.Results obtained in this study showed that,as for MinZhen No.2,the highest total antioxidant activities,DPPH radical scavenging activities,and ABTS radical scavenging activities were found for hexane fraction,ethyl acetate fraction,and butanol fraction,respectively,and their corresponding IC50 were 2.18 ± 0.14,3.46 ± 0.25 and 2.25 ± 0.01 mg/mL.As to MinZhen No.3,the highest total antioxidant activities,DPPH radical scavenging activities,and ABTS radical scavenging activities were exhibited by ethyl acetate fraction,and their corresponding IC50 were 3.12 ± 0.05,0.83 ± 0.01 and 1.57 ± 0.30 mg/mL,respectively.The correlation coefficient of DPPH radical scavenging activities and polyphenol contents from MinZhen No.2 and MinZhen No.3 was 0.7701 and 0.7954,respectively,suggesting that polyphenol contents had a relation with DPPH radical scavenging activities.3.Study on extraction and antioxidant activities of polysaccharides from two H.marmoreus strainsAntioxidant activities of polysaccharides and their various percent of alcohol precipitation fractions were investigated.As far as antioxidant activities of polysaccharides extracted from MinZhen No.2 and MinZhen No.3 is concerned,60%alcohol precipitation fraction of MinZhen No.3 polysaccharides exhibited the highest scavenging ABTS free radicals activity and the IC50 was 2.15 0.02 mg/mL;70%alcohol precipitation fraction of MinZhen No.3 polysaccharides displayed the highest scavenging activities for both DPPH free radicals and hydroxyl free radicals,and the IC50 were 0.93 ± 0.03 and 1.23 ± 0.06 mg/mL,respectively.Thus,The antioxidant activities of 60%and 70%alcohol precipitation fractions extracted MinZhen No.3 polysaccharides were higher.4.Analysis of volatile substances from two H.marmoreus strains by GC-MSThe volatile substances of MinZhen NO.2 and MinZhen NO.3 were extracted by headspace solid phase microextraction(HS-SPME),and subsequently analyzed by gas chromatography-mass spectrometry(GC-MS),respectively.Analysis results showed that MinZhen NO.2 and MinZhen NO.3 samples contained 11 and 12 known volatile substances,respectively,in which 5 were found to be common.However,6 volatile substances and 7 volatile substances were found to be MinZhen NO.2-specific and MinZhen NO.3-specific,respectively.The most amount of volatile substances in MinZhen No.2 was 2-ethyl-Hexanoic acid(18.27%),while that in MinZhen No.3 was Phenylethyl Alcohol(30.20%).Thus,volatile substances identified from MinZhen NO.2 and MinZhen NO.3 exhibited strain-common and strain-specific properties.The volatile substance differences of content and variety displayed by H.marmoreus strains might exert a major effect on their aromas. |
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