Natural deep eutectic solvents (NADESs) assisted extraction of essential oil from Nardostachys jatamansi (D.Don) DC with insecticidal activities

Different Natural deep eutectic solvents (NADESs) combinations were employed as a cosolvent in the conventional hydro-distillation method for extracting essential oil (EO) from the roots of Nardostachys jatamansi (D.Don) DC. Subsequent enhancement in EO yield along with phytochemical variation was observed on implementing NADESs as an extraction media compared to conventional hydro-distillation method using water. Among different combinations, the highest yield (1.7% v/w) of EO was observed with NADES-5 (choline chloride: maleic acid; 2:1) as compared to the conventional method (0.9% v/w, lowest yield among all combinations). Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis of all extracted EOs led to the identification of 34 compounds accounting for 76.13–87.87% of the total area percentage. Principal component analysis (PCA) and clustered heatmaps were used for multivariate analysis showing discrimination of the constituents in different EOs. Valeranone (31.22–12.60%) and nerolidol (21.39–1.82%) were observed in all samples, whereas some molecules like bisabolol, α-cadinol, and nootkatone were specific to certain samples, showing variability in chemical composition. EOs were further examined for their insecticidal and enzyme inhibitory activity against Aphis craccivora Koch (Hemiptera: Aphididae) and Planococcus lilacinus Cockerell (Hemiptera: Pseudococcidae), which are major sucking pests of legumes, vegetables, fruit and plantation crops. Results showed that the EOs obtained with water, NADES-4 (choline chloride: lactic acid; 1:2), 1 (choline chloride: oxalic acid; 1:1), 3 (choline chloride: lactic acid; 1:1), and 6 (glycerol: lactic acid; 1:1) showed promising toxicity (LD50 =0.80–0.98 µL/insect) against A. craccivora. Similarly, EOs obtained with water, NADES-3 (choline chloride: lactic acid; 1:1), and 4 (choline chloride: lactic acid; 1:2) also showed toxicity (LD50 =0.90–1.19 µL/insect) against P. lilacinus, which may be attributed to the presence of high concentration of metabolites such as valeranone, β-patchoulene, nerolidol, α-cadinol and viridiflorol. Further, LD50 concentrations of EO from water showed significant inhibition of glutathione S-transferase (8.52 ± 3.91 and 11.83 ± 5.68 nmol/min/mL) and acetylcholinesterase (0.67 ± 0.04 and 0.75 ± 0.09 mU/mg) after 24 h in A. craccivora and P. lilacinus, respectively.