Larvicidal effect and mechanism of action of the essential oil and major compound from Piper brachypetiolatum against Aedes aegypti larvae, with protection of non-target aquatic animals

Botanical larvicides, such as essential oils (EO) from the Piper species, offer eco-friendly mosquito control by targeting Culicidae larvae while exhibiting low toxicity to non-target aquatic animals. This study investigated the larvicidal activity and mechanism of action of the essential oil (EO) from Piper brachypetiolatum and its main compound, (E)-nerolidol, against Aedes aegypti, as well as the effects on non-target aquatic organisms Toxorhynchites haemorrhoidalis, Anisops bouvieri, and Diplonychus indicus. The EO was extracted from the leaves of P. brachypetiolatum using hydrodistillation, yielding 1.5 ± 0.7%. Gas chromatography revealed the presence of sesquiterpenes (64.70%), oxygenated sesquiterpenes (17.64%), monoterpenes (11.76%), and oxygenated monoterpenes (5.88%), with (E)-nerolidol as the major compound (64.32%). The EO and (E)-nerolidol exhibited significant larvicidal activity against A. aegypti, with LC₅₀ values of 15.51 and 9.50 mg/L, respectively. They also inhibited AChE activity (IC₅₀ values of 44.97 and 11.07 mg/L, respectively) and induced RONS overproduction (p < 0.05) compared to the positive control, α-cypermethrin. Additionally, the EO and (E)-nerolidol showed no lethal effects on T. haemorrhoidalis, A. bouvieri, and D. indicus, with these species exhibiting 100% survival after exposure. In contrast, α-cypermethrin caused 100% mortality in these species. These findings highlight the potential of the EO from P. brachypetiolatum and (E)-nerolidol as effective and environmentally friendly alternatives for controlling A. aegypti larvae.