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Antioxidant Properties and Polysaccharide Physicochemical Analysis of Ear Mushrooms
木耳類甲醇萃取物抗氧化性質之測定，抗氧化活性方面在1,3-二乙基-2-硫巴比妥酸法於濃度1.0~5.0 mg/mL時，油脂氧化率38.6~74.6%，而共軛雙烯法在濃度5.0 mg/mL時，紅耳、斤耳及雪耳具較佳的抗氧化力。還原力測定在濃度5.0 mg/mL時雪耳>黑耳≈ 紅耳≈ 斤耳>白木耳。捕捉1,1-二苯基-2-苦味基團（DPPH·）法中除了白木耳外其他均具有較佳的捕捉能力。木耳類捕捉羥自由基（hydroxyl radical）之能力不佳但具有良好之亞鐵離子螯合能力。在天然抗氧化成分方面，木耳類之甲醇萃取物中發現含有抗壞血酸、生育醇和總酚類化合物，但沒有偵測到b-胡蘿蔔素的存在，而總抗氧化成分含量為黑耳15.69 mg/g、紅耳30.09 mg/g、斤耳27.83 mg/g、雪耳49.17 mg/g、白木耳31.70 mg/g。
木耳類子實體之多醣萃取物分析，水萃取及鹼萃取多醣之總糖含量在74~92%，多醣體之單糖組成以木糖、甘露糖及醛糖酸為主，且有些含有葡萄糖之中性單糖組成。木耳類水萃取及鹼萃取多醣體經膠體過濾層析後得知其皆含有大於2 ×106 Da之大分子。以核磁共振氫光譜判定多醣結構具有RCH3-、RCH2-、CH3-CO-、CH2O-官能基存在，且可能有b-D-葡聚糖的化學位移。紅外線光譜上具有糖類官能基之吸光特性，得知水萃取多醣體具有-OH基、C-H基、C=O基、C=C基、C-O基、-CH-O-CH-基之吸收帶出現，而鹼萃取多醣體之差異是缺少C=O基、C-O基之吸收帶。多醣之示差熱掃瞄熱分析儀測定，結果發現多醣粉末屬於吸熱反應，除白木耳的水萃取及鹼萃取多醣各有一明顯的波峰外其他木耳類皆沒有明顯的吸熱峰，而其理化特性分析需更進一步探討。由以上所得結果及X光繞射儀分析結晶構形，得知木耳類之多醣體皆可能有b-D-葡聚糖之結構，但其明確機制仍有待進一步純化大分子多醣體後，再加以探討。
Wood ears are common edible fungi in China. Five kinds of wood ears are already commercially available in Taiwan, including black, red, jin, snow and silver ears. Mushroom fruit bodies and mycelia can be used as foods and food flavoring, to produce specifically chemical and medical substances, such as water soluble polysaccharides, vitamins, organic acids, nucleotides and enzymes, as well as to pharmaceuticals such as antibiotics, anticancer and antidisease drugs. In addition, mushrooms can supply antioxidant substances. However, so far no complete information is available for the antioxidant properties of wood ears in Taiwan. However, studies on the physiologically effects of wood ears have not been conducted. This research used wood ears as samples to study the proximate composition, antioxidant properties of methanolic extracts, the monosaccharide constituents and the structural analysis of polysaccharides. Their structures were elucidated by spectroscopic analysis and comparison with known compounds. For all methanolic extracts from ear mushrooms, the antioxidant activity in the 1,3-diethyl-2-thiobarbituric acid method were moderate (38.6~74.6%) at 1.0 to 5.0 mg/mL. Methanolic extracts for red, jin and snow ears showed excellent antioxidant activity in the conjugated diene method at 5.0 mg/mL. At 5.0 mg/mL, reducing powers in the descending order of sonw>black ≈ red ≈ jin>silver ears. The scavenging effect of methanolic extracts from ear mushrooms on 1,1-diphenyl-2-picryl hydrazyl radicals (DPPH·) was excellent except for that from silver ears. Ear mushrooms were not good scavengers for hydroxyl free radicals but good chelators for ferrous ions. Naturally occurring antioxidants, including ascorbic acid, tocopherols and total polyphenols, were found in methanolic extracts. However, b-carotene was not detected. Total antioxidant components were 15.69, 30.09, 27.83, 49.17, and 31.70 mg/g for black, red, jin, snow, and silver ears, respectively. In ear mushrooms, the total sugar contents of water extract and alkaline extract polysaccharides were 74~92%. The compositions of neutral monosaccharide were the major have xylose, mannose, glucuronic acid and some ears have glucose. Ear mushrooms of water extract and alkaline extract polysaccharides was separated using gel filtration, and showed a molecular weight of about 2×106 Da. Their structure were elucidated by 1H-NMR spectra of water extract and alkaline extract polysaccharides showed that they contained RCH3, RCH2, CH3-CO- and CH2O-. That can be have a b-D-glucan chain. IR spectroscopy showed that water extract polysaccharides contained OH, C-H, C=O, C=C, C-O, CH-O-CH-, but that alkaline extract polysaccharides not have C=O, C-O. The thermal behaviors of water extract and alkaline extract polysaccharides were examined by DSC, except for silver ear showed one endotherm but the anther not have. It could be study their physiological activities, advance analysis. The research and X-ray can be have a b-D-glucan chain. For the application in healthy food, further research on the mechanism of polysaccharide properties is in progress.
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