Insecticidal activity of a Tabernaemontana arborea root bark alkaloid extract against Culex quinquefasciatus larvae

The (sub-)tropical mosquito species Culex quinquefasciatus Say (Diptera: Culicidae) is a major vector for various parasitic and viral zoonotic diseases that pose a significant threat to human health. One promising source of effective and environmentally sustainable botanical insecticides against mosquitoes is the pantropical genus Tabernaemontana L. (Apocynaceae), which includes approximately 100 woody species known for producing bioactive monoterpenoid indole alkaloids (MIAs). We analyzed the alkaloid profile and insecticidal properties of a total alkaloid extract (TAE) obtained from the root bark of Tabernaemontana arborea ROSE ex J.D.SM. (Apocynaceae) against C. quinquefasciatus. According to gas chromatography-mass spectrometry (GC-MS), voacangine, ibogaine, vobasine, and coronaridine (82.99 %, 5.33 %, 4.62 %, and 1.97 % of the TAE's dry weight, respectively) were the main constituents of the TAE (2.42 % of the bark's dry weight), which demonstrated significant larvicidal activity (LC 50,90 = 1.56, 8.36 mu g/mL, 2.75, 13.42 mu g/mL, and 3.29, 13.95 mu g/mL for the second, third, and fourth instar, respectively). Both lethal and sublethal doses reduced the fecundity and vitality of the surviving mosquitoes without affecting the aquatic non-target species Daphnia magna Straus (Anomopoda: Daphniidae). Given the high yields of root bark and TAE, T. arborea shows promise as a source of sustainable botanical insecticides. It is a non-threatened species that thrives in disturbed areas across tropical and subtropical Mexico and can be easily propagated from seeds. However, further research, including laboratory and especially field studies, is needed to develop standardized formulations with MIAs from T. arborea that are effective, safe, and environmentally friendly.