Phenolics from Nigella sativa L. straw: Characterization and insecticidal activity against Agrotis ipsilon (Hüfnagel)

Abstract

The excessive production of food and agro-waste has become a significant problem for society, the economy, and the environment. To meet the growing demand for food free from harmful synthetic insecticides, a recent study has investigated the potential use of an ethanolic extract obtained from the straw of Nigella sativa L., a byproduct of seed collection, as a bioinsecticide. The study also evaluated its in-vitro and in-silico acetylcholinesterase (AChE) inhibitory potential against the Agrotis ipsilon (Hufnagel) moth species, which is known to cause damage to various crops and ornamental plants. The high-performance liquid chromatography examination revealed that the ethanolic N. sativa straw extract contained 18 phenolics, including 3 simple phenols, 8 phenolic acids, and 7 flavonoids. Catechol (330.14 μg/ml), chlorogenic (169.23 μg/ml), and gallic (110.93 μg/ml) acids were the predominant phenolics. On the other hand, catechin (94.07 μg/ml), naringenin (91.99 μg/ml), and rutin (78.16 μg/ml) were the major flavonoids identified in the extract. The insecticidal activity of the extract against the 4th larval instar of A. ipsilon was evaluated using four concentrations (1.25–10 %). The study found that higher extract concentrations led to increased mortality in the larvae. Specifically, the concentration of 10 % resulted in the highest mortality rate of 96.67 %. Lower concentrations of 5 %, 2.5 %, and 1.25 % resulted in mortality rates of 51.11 %, 18.89 %, and 9.17 %, respectively. The extract also showed higher activity against AChE in larval tissue, with an inhibition percentage of 65.2 % after 24 h of treatment. Docking experiments confirmed that ellagic acid and apigenin had higher binding affinity than the control (lanate). These results demonstrate the potential of utilizing agricultural waste like N. sativa straw to create innovative and sustainable bioinsecticides.