Cyperus rotundus L. is a widely distributed invasive weed plant with vast traditional medicinal uses. Herein, the methanolic root extract of C. rotundus and its fractions (n-hexane, chloroform, n-butanol, and aqueous) were evaluated for insecticidal activity against nymphs of Aphis craccivora Koch and crawlers of Planococcus lilacinus (Cockerell) to find promising lead (s). In contact topical assay, among extract/fractions, n-hexane fraction exhibited more toxicity against A. craccivora (LD50 = 1.12 μg/insect) and P. lilacinus (LD50 = 0.94 μg/insect). The chemical analysis of n-hexane fraction revealed a volatile composition similar to that of the essential oil (EO) of C. rotundus roots. Hence, EO was extracted using water and deep eutectic solvents (DESs) as cosolvent, which revealed enhancement in EO yield (from 0.28 to 0.46% w/w) on implementing DESs. A total of 35 diverse volatile metabolites were identified in all EO samples, accounting for 85.0 to 91.8% of chemical composition, having cyperotundone, cyperene mustakone, isolongifolen-5-one, boronia butenal as major constituents. The EO obtained with DES-7 [choline chloride: ethylene glycol (1:4)] and DES-6 [choline chloride: lactic acid (1:3)] were found effective against A. craccivora (LD50 = 0.62-0.87 μg/insect) and P. lilacinus (LD50= 0.59-0.67 μg/insect) after 96 h. NMR analysis of EO revealed cyperotundone as a major compound, which was isolated along with cyperene and cyperene epoxide. All the molecules were found effective against P. lilacinus, whereas against A. craccivora cyperotundone, cyperene and cyperene epoxide showed promising toxicity (LD50 = 0.74-0.86 μg/insect). Extract/fractions, EO, and isolated molecules showed a significant reproductive inhibition rate of A. craccivora at higher concentrations. All the tested concentrations of cyperotundone showed significant inhibition of acetylcholinesterase (AChE) and glutathione-S-transferase (GST) in A. craccivora and P. lilacinus. Based upon the present study, C. rotundus can be recommended to control targeted insects in the greenhouse/field conditions after performing bio-efficacy and phytotoxicity studies.
Keywords: AChE; Aphid; Cyperus rotundus; Efficacy; GST; Mealybug.
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