Yotsawimonwat Songwut, Sriroth Klanarong, Kaewvichit Sayam, Piyachomkwan Kaukoon, Jane Jay-Lin, Sirithunyalug Jakkapan
Department of Pharmaceutical Science, Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand.
Int J Biol Macromol. 2008 Aug 15;43(2):94-9. doi: 10.1016/j.ijbiomac.2008.03.006. Epub 2008 Apr 1.
Complex formations between debranched waxy rice starch (DBS) and fatty acids (FA) of different hydrocarbon chain lengths (8:0, 10:0, 12:0, 14:0, 16:0, and 18:0) were studied in an aqueous solution by measuring the blue colour stained with iodine. The objective of this study was to understand the effects of the solubility and hydrophobicity of guest molecules (FA) on the complex formation with DBS. Lauric acid (12:0) displayed the greatest complex forming ability with DBS by showing the least blue colour developed with iodine. The effect of pH (3-7) on the DBS/FA complex formation was evaluated by measuring the iodine-scanning spectra of the mixture. Short-chain FA (8:0) displayed less complex formation at pH>or=5, above the pK(a) of fatty acid (approximately 4.8), which suggested that the charge formation of the short-chain FA caused a lower partitioning of the FA into the hydrophobic cavity of the DBS single helix. On the contrary, FA of 10:0-18:0 displayed an increased complex formation at pH>5, which could be attributed to increased solubility of these longer-chain FA at a dissociated and ionized form. The hydrocarbon chain length of the FA had an important impact on the extent of the complex formation. A FA that had a shorter hydrocarbon chain was more soluble in an aqueous solution and more readily formed a complex with DBS. At pH 6 and 7 (above the pK(a)), 10:0 formed less inclusion complexes with DBS than did 12:0. Iodine-scanning spectra showed that the absorbances of all iodine-stained DBS/FA solutions at higher wavelength were substantially lower than that of the iodine-stained DBS alone, suggesting that FA preferentially formed inclusion complexes with DBS of longer chains.
通过测量碘染色的蓝色，研究了不同碳链长度（8:0、10:0、12:0、14:0、16:0和18:0）的脂肪酸（FA）与脱支蜡质大米淀粉（DBS）在水溶液中的复合形成。本研究的目的是了解客体分子（FA）的溶解度和疏水性对与DBS复合形成的影响。月桂酸（12:0）与DBS表现出最大的复合形成能力，碘染色显示的蓝色最少。通过测量混合物的碘扫描光谱，评估了pH值（3 - 7）对DBS/FA复合形成的影响。短链FA（8:0）在pH≥5时（高于脂肪酸的pK(a)，约为4.8）表现出较少的复合形成，这表明短链FA的电荷形成导致FA进入DBS单螺旋疏水腔的分配较低。相反，10:0 - 18:0的FA在pH>5时复合形成增加，这可能归因于这些长链FA以解离和离子化形式的溶解度增加。FA的碳链长度对复合形成程度有重要影响。碳链较短的FA在水溶液中更易溶解，更容易与DBS形成复合物。在pH 6和7（高于pK(a)）时，10:0与DBS形成的包合物比12:0少。碘扫描光谱表明，所有碘染色的DBS/FA溶液在较高波长下的吸光度均明显低于单独碘染色的DBS，这表明FA优先与较长链的DBS形成包合物。
