Gallic Acid, 3-Hydroxytyrosol, and Quercetin Modulate Cholinesterase Activity in Drosophila melanogaster

The current study investigates the modulatory effects of gallic acid (GA), 3-hydroxytyrosol (3-HT), and quercetin (QUE) on key cholinesterase enzymes using <i>Drosophila melanogaster</i> (fruit fly) head homogenates as a source of central cholinesterases following in vivo larval exposure. The choice of these plant phenolics was predicated on their cholinesterase (ChE) inhibitory effect reported recently by our group. The study utilized <i>D. melanogaster</i> larvae subjected to varying doses of GA, 3-HT, and QUE, subsequently evaluating enzymatic activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Galanthamine HBr was used as a positive control. All three phenolic compounds exhibited elevated ΔOD/min values for BChE inhibition compared to the negative control (ethanol). GA and QUE inhibited AChE, though with lower potency than galanthamine; at 1 mM, GA and QUE achieved 79.23% and 80.98% inhibition, respectively, compared to 98.34% for galanthamine. Interestingly, the effect of 3-HT on AChE was inversely related to the dose. The results indicate that GA and QUE modulate cholinesterase activity in vivo, consistent with our prior in vitro reports. This study also provides the first in vivo evidence of 3-HT's ChE-modulating activity in <i>Drosophila</i> within a whole-organism model.