菊苣酸抗氧化性及对抑制酪氨酸酶催化反应的动力学研究

Studies on the Antioxidative Activity and Inhibitory Kinetics on Tyrosinase-catalyzing Reaction of Cichoric Acid

以DPPH、·OH的清除效果和铁还原力为指标,采用酶动力学方法研究菊苣酸的抗氧化活性和对酪氨酸酶单酚酶和二酚酶的影响及抑制作用。结果表明:菊苣酸对DPPH、·OH自由基的清除率和铁还原力与菊苣酸浓度呈线性量效关系,IC_(50)值分别为13.63,14.26和13.78 mg/L。菊苣酸对酪氨酸酶单酚酶和二酚酶均具有较好的抑制作用,对单酚酶和二酚酶活性抑制的IC_(50)值分别为0.26 mmol/L和0.71 mmol/L,显著小于熊果苷对二酚酶活性抑制的IC_(50)值(5.3 mmol/L)。菊苣酸能明显延长单酚酶的迟滞时间。在浓度为0.40 mmol/L时,菊苣酸可使迟滞时间由134 s延长至383 s,延长2.87倍。Lineweaver-Burk菊苣酸对二酚酶的抑制表现为可逆竞争型抑制,最大反应速率(vm)为83.30μmol/L,抑制常数(KI)为0.14 mmol/L。

The antioxidative activity and inhibitory kinetics of cichoric acid on monophenolase and diphenolase of mushroom tyrosinase were investigated by enzymological kinetic analysis method using DPPH and ·OH free radical scavenging activity and ferric reducing antioxidant power（FRAP） as indicators. It was found that the ability to scavenge DPPH and ·OH free radicals, ferric reducing antioxidant power appeared in a linear concentration-dependent manner of cichor-ic acid. The IC_（50） values were 13.63, 14.26 mg/L and 13.78 mg/L, respectively. In addition, cichoric acid can efficiently inhibit both monophenolase and diphenolase activities of tyrosinase. The cichoric acid concentrations corresponding to 50% inhibitory rate on monophenolase and diphenolase activity were 0.26 mmol/L and 0.71 mmol/L, which were much lower than arbutin for diphenolase activity（IC_（50）=5.30 mmol/L）. Cichoric acid at a concentration of 0.40 mmol/L can obvi ously extend the lag time from 134 s to 383 s in the oxidation process of L-tyrosine via tyrosi-nase. The time increased2.87 times. Lineweaver-Burk plot demonstrated a reversible competitive behavior of cichoric acid in the tyrosinase oxidation of L-DOPA, with maximum reaction rate vm and inhibition constant KIat 83.3 μmol/L and 0.139 mmol/L, respectively.