Efficiency of some inhibitors on alpha amylase of the peach fruit fly larvae Bactrocera zonata (Saunders) (Diptera: Tephritidae)

Alpha amylase inhibitor (α-AI) extracted from wheat grains (Triticum sp.) as possible new agent in pest control, and some other organic inhibitors are evaluated against α-amylase of the fourth larval instar of the peach fruit fly (PFF) larvae; Bactrocera zonata (Saund.). 4.2 mg protein ml⁻¹ of the inhibitor extracted by 70 % ammonium sulphate inhibited, in vitro, 97.9 % of amylolytic activity of the larvae. Percent inhibition efficiency (Ei%) of the crude inhibitor was directly proportional with its concentration in the range from 4.2 to 0.21 mg protein ml-1. The calculated IC50 was 1 mg protein ml-1. Increasing of the surrounding temperature from 10 to 35 °C not enhanced inhibitor efficiency, and the inhibitor could inhibit the enzyme efficiently at a relatively low temperature (10 °C). On the other hand, wheat extract showed quick binding affinity to α-amylase of PFF larvae. Incubation of the inhibitor with the enzyme for 10 min was sufficient for wheat α- AI to exert its maximum inhibition. Screening of other possible organic compounds act as α-AI such as citric, gallic and acetic acids showed that gallic acid was the most potent inhibitor, and it was able to inhibit α-amylase of the larvae, at a relatively, low concentration (10⁻⁴M). It could be concluded that there are natural potent inhibitors of PFF α-amylase which act as a key enzyme for carbohydrates digestion. This might be useful as an alternative method for controlling B. zonata population. Additional experiments are necessary to make these alternative compounds applicable in the field.