| 摘要: | 幾丁質聚醣是N- 乙醯葡萄糖胺( N-acetyl-D-glucosamine ) 或N- 葡萄糖胺（N-D-glucosamine）單體以β-1,4 鍵結所構成之高分子聚合物。幾丁聚醣與其衍生物具有多種功能性質而被開發成多方面用途，例如廢水處理、生化上用來固定酵素、醫療上用於外科手術縫合線和膠囊材料等。在食品上的應用則因幾丁質及幾丁聚醣具有可食性及熱穩定性，可作為凝膠劑、增稠劑等的食品添加物，且其不容易被人體所吸收，可做為動物來源膳食纖維（Shahidi, et al., 1999）。儘管幾丁聚醣具有廣泛的應用性，但在應用過程中，卻往往因其在水中之溶解度很小，使其應用之範圍遭受到限制。幾丁聚醣在 pH 值小於6.5 的酸溶液中帶正電，幾丁聚醣的功能性大多因其帶正電性可吸引帶負電性的物質。例如，生物組織（皮膚、骨頭和頭髮）、多醣（褐藻膠）、細菌和黴菌、酵素和微生物細胞均帶負電。幾丁聚醣可做為食物保鮮劑，但因其不能溶解在中性甚至較高pH 值的溶液中，使其應用之範圍遭受到限制（sugimoto, et al., 1998）。藉由化學修飾反應，使幾丁聚醣具有溶於水之特性，可拓展幾丁聚醣之應用範圍(Yalpani and Hall, 1984; Holme and Pelin, 1997; Yang et al., 2002; 2005a; 2005b; 2007; Sugimoto et al., 1998) 。目前幾丁聚醣衍生物的研究非常多，例如幾丁聚醣烷基化（alkylation）衍生物(Yang et al., 2002; 2005a; 2005b; 2007) ，但是關於幾丁聚醣氨烷基化（aminoalkylation）衍生物在抗菌與吸附重金屬能力方面的文獻很少。而幾丁聚醣的生物活性（biological activities）歸因於其多價陽離子性質，若幾丁聚醣的胺基進行化學反應後帶有正電之胺基減少則其生物活性可能會喪失。故本研究擬分別利用quaternization 與aminoalkylation 兩種反應(scheme 1 和2)，將2-chloroethylamino hydrochloride 與幾丁聚醣分子上葡萄醣胺單元的C2 之胺基、C3 之氫氧基和C6 之氫氧基產生鍵結來增加胺基與帶電性，並改善幾丁聚醣的溶解性質。進一步探討幾丁聚醣衍生物之抗菌、抗氧化與其流變性質。
Chitosan, an aminopolysaccharide, comprises unbranched chain of β (1 → 4)2-amino-2-deoxy-D-glucan residues. Chitosan and its derivatives have been considered for various applications including flocculation and coagulation in food processing, heavy-metal ion recovery from waste waters, and the fabrication of structural matrices for food, cosmetic, biotechnological and biomedical applications (Shahidi, et al., 1999). However, chitosan-related applications are limited by its insolubility at neutral or high pH values (Sugimoto, et al., 1998). Chitosan is an unbranched cationic biopolymer in acidic media, i.e. it carries a positive charge at pH below 6.5. Many uses of chitosan are based on its positive charge, which is attracted to negatively charged materials. Most living tissues (e.g. skin, bone, hair); polysaccharides (e.g. alginate); polyanions; bacteria and fungi; enzymes and microbial cells are negatively charged. Despite the unique antimicrobial property, the application of chitosan as a food preservative and for other use was limited by its insolubility at neutral and higher pH (Sugimoto et al., 1998). Therefore, in the past two decades extensive investigations have been carried out to prepare functional derivatives of chitosan, and to increase its solubility in water in order to broaden its application (Yalpani and Hall, 1984; Holme and Pelin, 1997; Yang et al., 2002; 2005a; 2005b; 2007; Sugimoto et al., 1998). Several alkylated chitosans are reported to be synthesizd (Yang et al., 2002; 2005a; 2005b; 2007), howere, to the best of our knowledge, optimized preparation of 2-chloroethylamino hydrochloride with chitosan, has not been yet reported for antibacterial and metal-adsorption purposes. Most biological activities of chitosan are attributed to their free amino group. Therefore, in this study, we modified C3、C6 position or amino group of chitosan with -chloroethylamino hydrochloride, and investigated antibacterial 、antioxidant and rheological property of water-soluble chitosan derivatives. |
