Using nanoemulsions of the essential oils of a selection of medicinal plants from Jazan, Saudi Arabia, as a green larvicidal against Culex pipiens.

Researchers are increasingly looking to plants as sources of novel ingredients active against vector-borne diseases. Medicinal plant extracts and their metabolites are an attractive source for such products. This study investigated the insecticidal activity of five essential oils extracted from the most common medicinal herbs in Jazan province, Kingdom of Saudi Arabia. Extracted oils and nanoemulsions synthesized from those oils were characterized before application at different concentrations to laboratory-reared fourth-stage larvae of Culex pipens. Basil (Ocimum bascilicum) and cumin (Cuminum cyminum) essential oils showed moderate larvicidal effect with LC50 81.07 ug/mL and 96.29 ug/mL, respectively. That activity was improved in their nanoemulsion forms, as evidenced by a reduction in the LC50 to 65.19 ug/mL for basil and 64.50 ug/mL for cumin. Clove (Syzygium aromaticum), henna (Lawsonia inermis) and ginger (Zingiber officinalis) oils showed weaker insecticidal activity, with LC50 values of 394 ug/mL, 306 ug/mL, and 494 ug/mL, respectively. Moreover, the nanoemulsion forms of those essential oils did not show any improvement in their insecticidal activity. In conclusion, of the studied plants, the nanoemulsions of basil and cumin showed significant larvicidal activity

Synthesis and efficacy of cinnamon oil formulations and their sustainable release against common house mosquito larvae

Abstract Background Control of mosquitoes is considered an essential public health priority. This study was designed to estimate the larvicidal activity of two formulations of Cinnamomum zeylanicum EO for controlling Culex pipiens larvae. Results The prepared formulations were a nanoemulsion of cinnamon (CNE), cinnamon (CN) alone and ordinary cinnamon essential oil mixed with sesame oil (CSO). The cinnamon + sesame oil (CSO) was added as one part cinnamon to 3 parts SO. Different concentrations were prepared and applied following the WHO larvicidal bioassay protocol. Our findings revealed that the LC50 of the CNE form ranged from 85.3 µg/mL to 28.30 µg/mL. The LC50 of SO alone was 1265 µg/mL but when mixed with CNE to form the CSO mixture, this decreased to 159.00 µg/mL. In terms of residual effect, the ordinary form of cinnamon had a residual effect in water for 72 h at a dose of 1000 µg/ml, but this extended to 120 h at the same dose when the CNE form was used. However CSO did not have a residual effect, however. Conclusion The nanoemulsion form significantly improved the efficacy and residual effect of cinnamon against Culex pipiens larvae. Additionally, mixing cinnamon with sesame oil had a synergistic effect. This may assist control strategies against the house mosquito, Culex pipiens

Rhipicephalus annulatus (Acari: Ixodidae) Control by Nigella sativa, Thyme and Spinosad Preparations

Background: Several compounds obtained from plants have potential insecticidal, growth deterrent or repellent characteristics. The control of hard ticks by non-chemical substances was targeted in this study. Methods: The effect of 36 materials on in-vitro ticks was studied, including 2 absolute controls (water only or ab­solute ethyl alcohol only), 6 conventionally used spinosad preparations (aqueous solutions), 12 Nigella sativa (N. sativa) preparations (aqueous and alcoholic solutions), and 12 Thyme preparations (aqueous and alcoholic solutions). The engorged ticks were tested in-vitro for mortality and oviposition ability using the studied materials. Results: The final mortality after 48 hours of application in N. sativa aqueous preparations began from 10.0% con­centration, 1.0% to 100% by concentration preparations ≥10%. In addition, N. sativa alcoholic preparations began from 50.0% concentration, 2 % to 100% by concentration ≥5%. Meanwhile, Thyme aqueous and alcoholic prepa­rations began from 70.0% concentration, 5% to 90% by concentration 10–20%. Additionally, spinosad aqueous preparations and both of control preparations (Water and Alcohol) resulted in no mortality. All differences were sta­tistically significant. The oviposition was stopped in N. sativa (aqueous ≥10% and alcoholic ≥5%) and in spinosad (aqueous≥25%). The aqoues dilution of the used matters killed B. annulatus larvae beginning from the concentration 5%. Conclusion: Nigella sativa alcohol 20% was the best of studied preparations being the lowest concentration (20%) that could achieve the highest lethal (100%) effect in shortest time (12 hours). Moreover, Thyme oil and spinosad could not kill 100% of adult but did on larvae

Mosquitocidal Activity of the Methanolic Extract of <em>Annickia</em><em> chlorantha</em> and Its Isolated Compounds against <em>Culex pipiens</em>, and Their Impact on the Non-Target Organism Zebrafish, <em>Danio rerio</em>

In this study, the crude extract and its isolated compounds from the stem bark of Annickia chlorantha were tested for their larvicidal, developmental, and repellent activity against the mosquito vector, Culex pipiens, besides their toxicity to the non-target aquatic organism, the zebrafish (Danio rerio). The acute larvicidal activity of isolated compounds; namely, palmatine, jatrorrhizine, columbamine, β-sitosterol, and Annickia chlorantha methanolic extract (AC), was observed. Developmentally, the larval duration was significantly prolonged when palmatine and β-sitosterol were applied, whereas the pupal duration was significantly prolonged for almost all treatments except palmatine and jatrorrhizine, where it shortened from those in the control. Acetylcholinesterase (AChE) enzyme showed different activity patterns, where it significantly increased in columbamine and β-sitosterol, and decreased in (AC), palmatine, and jatrorrhizine treatments, whereas glutathione S-transferase (GST) enzyme was significantly increased when AC methanolic extract/isolated compounds were applied, compared to the control. The adult emergence percentages were significantly decreased in all treatments, whereas tested compounds revealed non-significant (p > 0.05) changes in the sex ratio percentages, with a slight female-to-male preference presented in the AC-treated group. Additionally, the tested materials revealed repellence action; interestingly, palmatine and jatrorrhizine recorded higher levels of protection, followed by AC, columbamine, and β-sitosterol for 7 consecutive hours compared to the negative and positive control groups. The non-target assay confirms that the tested materials have very low toxic activity compared to the reported toxicity against mosquito larvae. A docking simulation was employed to better understand the interaction of the isolated compounds with the enzymes, AChE and GST. Additionally, DFT calculations revealed that the reported larvicidal activity may be due to the differing electron distributions among tested compounds. Overall, this study highlights the potential of A. chlorantha extract and its isolated compounds as effective mosquitocidal agents with a very low toxic effect on non-target organisms