Study On Enzymatic Hydrolysis Preparation Of Oligogalacturonic Acid And The Effect Of Its Complex With Cu～(2+) On Rat's Growth Performance

In this paper, oligogalacturonic acid was prepared by four different pectases hydrolysis of apple pectin and pectic acid, wherein, the optimum pectase was Pectinex XXL, the optimum substrate was pectic acid, and the optimum reaction conditions were: pH 5.5, 55℃, reaction time 30 min, the quantity of pectase: pectic acid=1:10 (2% pectic acid). Under these conditions, the oligogalacturonic acid was detected by thin-layer chromatography (TLC) and high-performance anion-exchange chromatography (HPAEC). The yield of the oligogalacturonic acid was more than 54.3%, mainly with a degree of polymerization (DP) 2 and 3, the yields of which were 26.7% and 27.6% respectively. The oligogalacturonic acid was separated by two steps silica column chromatography, from which 31.8 mg digalacturonic acid and 24.0 mg trigalacturonic acid were obtained. Both compounds were structurally characterized by ESI-MS,¹H NMR, ¹³C NMR,¹H-¹H COSY and ¹H-¹³C HMQC. The digalacturonic acid was (1,4) linked oligomer of two unmethylated a-galacturonic acids, and the trigalacturonic acid was (1,4) linked oligomer of three unmethylated a-galacturonic acids. The purity of both oligomers was upwards of 95%. A complex of oligogalacturonic acid with Cu²⁺ was formed in the mixture of 5% oligogalacturonic acid solution and 0.2 M CuSO₄ solution (1:1, v/v) at room temperature. The yield of the complex was 51.5%. The Cu²⁺ content of the complex was 20.8%. CuSO₄ and the complex containing the same amounts of Cu²⁺ were added into the feed for rat separately. The rat's growth performance was studied. To achieve the same growth promoting effect as the complex of oligogalacturonic acid with Cu²⁺, more than 3 times Cu²⁺ contained in CuSO₄ was needed. Compared with the effects of CuSO₄, the complex of oligogalacturonic acid with Cu²⁺ promoted the growth of rat by 3 times, and reduced the contents of Cu²⁺ in the liver, blood and fece of rat by 38.3%, 11.8% and 52.0% respectively.