INHIBITORY EFFECT OF CRUDE ALKALOIDS OF DATURA STRAMONIUM SEED AND IT’S FRACTION(S) ON ACETYLCHOLINESTERASE ISOLATED FROM RESISTANT AND SUSCEPTIBLE ANOPHELES GAMBIAE MOSQUITO LARVAE

Williams D.G. Chintem; Mahmoud Sulieman Jada; Shehu Sarkiyayi; Abdullahi Usman Wurochekke

doi:10.47743/jemb-2024-271

Authors

Williams D.G. Chintem Modibbo Adama University Yola
Mahmoud Sulieman Jada Modibbo Adama university Yola
Shehu Sarkiyayi Modibbo Adama University, Yola
Abdullahi Usman Wurochekke

DOI:

https://doi.org/10.47743/jemb-2024-271

Keywords:

Datura stramonium, Acetylcholinesterase, Anopheles gambiae larvae, Alkaloid, Insecticide resistance, Non-competitive inhibition

Abstract

The increasing resistance of Anopheles gambiae to conventional neurotoxic insecticides necessitates the exploration of alternative acetylcholinesterase (AChE) inhibitors with novel modes of action. This study evaluated the inhibitory effects of crude alkaloids and alkaloid fractions from Datura stramonium seeds on AChE isolated from susceptible (sAChE) and resistant (rAChE) Anopheles gambiae larvae. Crude alkaloids were extracted using acid–base partitioning, while mosquito larvae were field-collected, reared, and biochemically characterized. AChE was isolated from larval homogenates, and enzyme inhibition assays were conducted using the Ellman Assay. Enzyme kinetics (K_m and V_max), optimal pH and temperature, and modes of inhibition were also determined. The crude alkaloid extract inhibited AChE in a concentration-dependent manner, with higher sensitivity observed in sAChE (IC₅₀ = 30.3 µg/mL) compared to rAChE (IC₅₀=59.6 µg/mL). Among the alkaloid fractions, DSAF-3 exhibited the strongest inhibitory activity against both strains, achieving up to 89% inhibition at 100 µg/mL and the lowest IC₅₀ (22.8 µg/mL). In contrast, the standard insecticide temephos showed greater potency against rAChE than sAChE, reflecting differential target-site sensitivity. Optimal AChE activity for both strains occurred at pH 7.0–7.5 and 40°C. Kinetic analysis revealed that crude alkaloids and DSAF-3 caused significant reductions in V_max (rAChE=0.9802, sAChE=0.4975) and (rAChE=0.7675, sAChE=0.1507) with relatively unchanged Km values , indicating predominantly non-competitive inhibition, unlike temephos, which exhibited mixed inhibition. These research findings demonstrate that D. stramonium seed alkaloids, particularly fraction DSAF-3, effectively inhibit both susceptible and resistant AChE through a resistance-insensitive mechanism, highlighting their potential as lead compounds for the development of novel larvicidal agents in malaria vector control.

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