单宁酸对甜菜夜蛾幼虫生长发育及酚氧化酶活性的抑制作用

Inhibitory effect of tannic acid on growth,development and phenoloxidase activity of Spodoptera exigua larva

采用摄食毒力法研究了单宁酸对甜菜夜蛾〔Spodoptera exigua(Hübner)〕幼虫生长发育的影响及毒力作用,并分析了单宁酸对甜菜夜蛾酚氧化酶的抑制动力学。结果表明,不同质量浓度单宁酸对甜菜夜蛾初孵幼虫具有较强的毒杀作用,对3龄幼虫的体质量以及蛹质量、化蛹及羽化过程也均有明显的抑制作用(P<0.05)。随单宁酸质量浓度的提高或处理时间的延长,甜菜夜蛾初孵幼虫的校正死亡率逐渐增大,单宁酸的抑制生长效应逐渐增强,处理第7天,单宁酸对试虫的半致死浓度(LC50)为3.772 3 g.L-1;8 g.L-1单宁酸对3龄幼虫体质量增长的抑制率最高(35.09%);16 g.L-1单宁酸对蛹质量和羽化率的影响最明显。单宁酸能明显抑制甜菜夜蛾酚氧化酶的活力,且随单宁酸浓度的提高,酚氧化酶相对活力下降趋势明显趋缓,单宁酸对甜菜夜蛾酚氧化酶活性的半抑制浓度(IC50)为0.234 3 mmol.L-1;在加入不同浓度单宁酸的反应体系中,酚氧化酶的活力与酶液量呈明显的线性关系;不同浓度单宁酸对甜菜夜蛾酚氧化酶抑制作用的Lineweaver-Burk双倒数图为1组横轴截距不变的直线;另外,单宁酸和半胱氨酸均可将多巴醌还原为多巴,且还原量均随反应时间的延长而增加。研究结果说明,单宁酸对甜菜夜蛾酚氧化酶的抑制作用是可逆的,为典型的非竞争性抑制剂,抑制常数(Ki)为0.193 8 mmol.L-1;单宁酸对甜菜夜蛾酚氧化酶二酚酶的抑制作用与L-多巴氧化产物的还原有关。

Toxicity effect of tannic acid on growth and development of Spodoptera exigua（Hübner） larva were studied by feeding toxicity method,and its inhibition kinetics on phenoloxidase of S.exigua was also analyzed.The results show that tannic acid with different concentrations has a stronger toxicity effect on S.exigua newly hatched larva and also has an obvious inhibitory effect on weight of 3rd instar larva and pupa weight,pupation process and emergence process（P〈0.05）.The corrected mortality of S.exigua newly hatched larva increases gradually with increasing of tannic acid concentration or prolonging of treatment time,and its inhibitory effect on larva growth enhances gradually.The median lethal concentration（LC50） of tannic acid to the larva treated for 7 d is 3.772 3 g·L^-1.The inhibition rate of 8 g·L^-1 tannic acid to weight increment of 3rd instar larva of S.exigua is the highest with a value of 35.09%,and the inhibitory effects of 16 g·L^-1 tannic acid on pupa weight and emergence rate are the most obvious.Tannic acid can obviously inhibit phenoloxidase activity of S.exigua,and downtrend of phenoloxidase relative activity is obviously slow with increasing of tannic acid concentration,and its hemi-inhibitory concentration（IC50） on phenoloxidase activity of S.exigua is 0.234 3 mmol·L^-1.In reaction systems added tannic acid with different concentrations,there is obvious linear relationship between phenoloxidase activity and enzyme solution volume.And Lineweaver-Burk double reciprocal graphes for inhibition of different concentrations of tannic acid to phenoloxidase activity of S.exigua are a group of linears with invariant intercept of abscissas.Otherwise,both of tannic acid and cysteine can reduce dopaquinone to dopa,and the reduction amount increases with prolonging of reaction time.It is suggested that the inhibitory effect of tannic acid on phenoloxidase activity of S.exigua is reversible,and tannic acid is a typical noncompetitive inhibitor with an inhibition constant（Ki） of 0.193 8 mmol·L^-1.And the inhibitory effect of tannic acid on phenoloxidase diphenolase of S.exigua is related to reduction of L-dopa oxidation products.