A novel herbal product based on Piper betle and Sphaeranthus indicus essential oils: toxicity, repellent activity and impact on detoxifying enzymes GST and CYP450 of Aedes aegypti Liston (Diptera: Culicidae)

Fresh leaves of Piper betle Linn. (Piperales: Piperaceae) and Sphaeranthus indicus Linn. (Asterales: Asteraceae), commonly known as betel leaves and East Indian globe thistle, respectively, were harvested and steam distilled for the extraction of P. betle and S. indicus crude volatile oils (Pb-CVO and Si-CVO, respectively). LC50 calculated on 3rd instar larvae of dengue mosquito Aedes aegypti Linn. (Diptera: Culicidae) was 42.17 ppm for PbSi-CVO (i.e., herbal formulation based on the EOs of P. betle and S. indicus). The larval and pupal duration were significantly longer post-treatment with 100 ppm of PbSi-CVO, if compared to control. We observed that PbSi-CVO significantly altered the detoxifying enzymes GST and CYP450 compared to the expression of control. Sub-lethal concentrations of PbSi-CVO showed strong repellent properties against dengue mosquitoes, without adverse reactions on the volunteers experiencing the repellent assays. Lastly, the adulticidal activity of PbSi-CVO was studied. Overall, our study outlined that this herbal product represents a promising candidate for the development of botanical based adulticidal agents.