Exploring the potential of Fabiana imbricata Ruiz et Pav. (“Pichi”) against pest insects and pathogenic microorganisms for crop protection

The loss of agricultural products by pests and microorganisms is intensely fought with synthetic products that can pose a serious threat to the environment, health, and foods. The use of plant-derived products in the management of these organisms is a sustainable and safe alternative. In this study, we investigated Fabiana imbricata, a very well-known species of Solanaceae found in the Patagonian region. The toxicological effects of its fractions were tested against Drosophila melanogaster and Tenebrio molitor. These fractions were also screened for repellency on Acanthoscelides obtectus and antimicrobial activity. Additionally, the mortality assay of D. melanogaster larvae revealed higher activity for the stem (LC50 value of 7.5 µg/mL) and leaf (LC50 value of 19.8 µg/mL) petroleum benzine fractions. Tenebrio molitor larvae needed to be exposed to a high concentration of stem fractions (200 and 300 µg/mL) to observe about 50 and 90% mortality, respectively. Moreover, repellency after 4 h of exposure was mainly observed with the stem dichloromethane fraction (conc. 100 µg/mL). The acetate fraction of the stem (FE-C) was responsible for the greatest growth inhibition of the tested bacteria (Escherichia coli, Listeria monocytogenes, L. innocua, Salmonella sp., and S. aureus). Based on the findings, stem fractions were selected for studies of toxicity in non-target organisms and systemic effects on proteins and detoxification enzymes from T. molitor larvae. The fractions tested against adult bees were safe up to 500 µg/mL for 4 h of exposure and 48 h of observation. Total proteins and enzymes AChE, GST/GSH, and Carboxylase were significantly reduced, mainly with FE-C. In contrast, ACP and ALP were up-regulated, with the same fraction as the major inducer. The chemical profiles of the fractions analyzed by GC-MS and NMR showed that FE-C had scopoletin as the main component. Therefore, we selected this compound for in silico analysis of AChE docking, qualitative and quantitative study of insecticide-likeness, and toxicity prediction. The results indicated that scopoletin efficiently docked with the active site of AChE. Due to the high values ​​of Relative Drug Likelihood (RDL) (2.77) and Gaussian Scoring Function (GAU) (4.19) values, ​​it can consider as potential insecticide-likeness and the toxicity prediction study showed that this compound has low toxicity to mammals. These results demonstrate that FE-C has potential as an insecticidal agent against insect pests and can be of help in combating pathogenic microorganisms present in food.