ORIGINAL RESEARCH ARTICLE Biomolecular alterations by chronic sub-lethal exposure of Malathion and Paraquat in Drosophila melanogaster: study on pesticide tolerance in insects Mohammad Murtaza Mehdi 1 & Mohammad Layqat 2 & Saima Majid 2 Received: 19 November 2019 /Accepted: 30 March 2020 # African Association of Insect Scientists 2020 Abstract Pesticides exert a wide variety of functions for controlling pests. At low doses the pests are not much affected and parallel to that a chance of tolerance has been expected. In this study a population of fruit flies Drosophila melanogaster was grown under various doses of insecticide Malathion and herbicide Paraquat. Lower than the sub-lethal doses (0.2 micromolar), various biomolecular alterations in terms of protein oxidation (Advanced Oxidation Protein Products, AOPP), lipid peroxidation (Malondialdehyde, MDA), sialic acids, total thiols, Cupric Ion Reducing Antioxidant Capacity (CUPRAC) and 2,2′-Azino-bis(3-ethylbenzothiaz- oline-6-sulfonic acid) (ABTS) cation radical scavenging activity have been observed. Positive alteration in AOPP for both Malathion and Paraquat treated fruit flies as well as increased MDA content in Paraquat treated flies are the alterations in the fruit fly population because of oxidative stress. The unaffected MDA, sialic acid content and CUPRAC antioxidant capacity for Malathion treated flies demonstrates the diminished effects of oxidative stress exerted through Malathion. There is increase sialic acid and CUPRAC antioxidant capacity after treatment of Paraquat. There is also an increase in total thiols and ABTS cation radical scavenging activity after treatment of both Malathion and Paraquat. These results evidently show that improved antiox- idant mechanisms effectively alleviate the oxidative stress exerted by pesticides. This study is clearly reflecting that oxidative stress generated by the sub lethal doses of pesticides can be diminished and certain tolerance level is also achieved by the insects in terms of increased antioxidant defence and longevity. Keywords Pesticide tolerance . Protein oxidation . Lipid peroxidation . Total thiols . Antioxidant activity Introduction Pesticides, that are used to eliminate insects, fungus, unwanted herbs and the other pests, play important role in avoiding dis- eases and preventing the damage of property (Kumar and Kumar 2019; Yadav and Devi 2017). These compounds, which may be containing an active and inert ingredient, can be broadly divided based on their target organisms like insecticides (for insects), herbicides (for weeds), rodenticides (for rodents) and fungicides (for fungi and molds) (Randall et al. 2008; Sifakis et al. 2011). Pesticides on the basis of action, can be grouped as ruining, repelling and extenuating agents (Speck-Planche et al. 2012). Depending upon the population level, their properties rely upon different factors such as existence, features and time of implementation (Schmolke et al. 2010). Pesticide tolerance is considered as the natural ability to withstand against action of pesticide and unlike resistance it may not necessarily be the result of genetic changes caused by the insecticide selection pressure (Wu et al. 2017; Zhu 2008). Highlights • Tolerance against pesticides is observed when fruit flies are exposed to lower doses of Malathion and Paraquat • Antioxidant defence system is observed to respond in affirmative manner against the exposure • Few biomolecules are not affected by the oxidative stress produced • Comparative longevity is increased in pesticide exposed fruit flies • Total thiols are positively corroborated against the exposure * Mohammad Murtaza Mehdi mehdibiochem@gmail.com 1 Department of Biochemistry, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab 144411, India 2 Department of Zoology, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India International Journal of Tropical Insect Science https://doi.org/10.1007/s42690-020-00143-6