Datura metel-synthesized silver nanoparticles magnify predation of dragonfly nymphs against the malaria vector Anopheles stephensi.

Malaria is a life-threatening disease caused by parasites transmitted to people and animals through the bites of infected mosquitoes. The employ of synthetic insecticides to control Anopheles populations leads to high operational costs, non-target effects, and induced resistance. Recently, plant-borne compounds have been proposed for efficient and rapid extracellular synthesis of mosquitocidal nanoparticles. However, their impact against predators of mosquito larvae has been poorly studied. In this study, we synthesized silver nanoparticles (AgNPs) using the Datura metel leaf extract as reducing and stabilizing agent. The biosynthesis of AgNPs was confirmed analyzing the excitation of surface plasmon resonance using ultraviolet-visible (UV-vis) spectroscopy. Scanning electron microscopy (SEM) showed the clustered and irregular shapes of AgNPs, with a mean size of 40-60 nm. The presence of silver was determined by energy-dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy analysis investigated the identity of secondary metabolites, which may be acting as AgNP capping agents. In laboratory, LC50 of D. metel extract against Anopheles stephensi ranged from 34.693 ppm (I instar larvae) to 81.500 ppm (pupae). LC50 of AgNP ranged from 2.969 ppm (I instar larvae) to 6.755 ppm (pupae). Under standard laboratory conditions, the predation efficiency of Anax immaculifrons nymphs after 24 h was 75.5 % (II instar larvae) and 53.5 % (III instar larvae). In AgNP-contaminated environment, predation rates were boosted to 95.5 and 78 %, respectively. Our results documented that D. metel-synthesized AgNP might be employed at rather low doses to reduce larval populations of malaria vectors, without detrimental effects on behavioral traits of young instars of the dragonfly Anax immaculifrons.

[Scopolamine and hyoscyamine synthesis in hair roots culture of Datura metel].

OBJECTIVE: To establish the hair roots culture system of Datura metel and study the hair roots growth and biosynthesis of scopolamine and hyoscyamine in hair roots culturing system. METHOD: Direct degermed cotyledon of wild D. metel was infected by Agrobacterium tumefaciens strain C58C1 to obtain hair roots. Growth curves and scopolamine and hyoscyamine biosynthesis curves were determined. The scopolamine and hyoscyamine from different hair roots lines were examined by HPLC. RESULT: Hair roots induction rate reached 70%. After 25 days cultured in 1/2 MS liquid nutrient medium, the hair roots weight, content of scopolamine and hyoscyamine reached maximum, tow high efficient accumulation hyoscyamine and scopolamine hair roots lines M1 and M2 were obtained. The medial accumulation coefficient of hyoscyamine and scopolamine were 2.53 times and 5.37 times compared with the leaves of wild D. metel respectively. CONCLUSION: The established hair roots induction and culture system of D. metel provided a foundation for further obtaining scopolamine and hyoscyamine.