Abstract:
This study aims to evaluate the acute toxicity of biosynthetic AgNPs produced using Annona glabra leaf extract, against a selected aquatic-indicator, Daphnia magna. The toxicity of the biosynthetic AgNPs was compared against the Ag+ ion solution. Aqueous leaf extracts of A. glabra were prepared by heating chopped leaves (20.0 g) with water (100.0 mL) at 100 oc for 1 hour. AgNPs were synthesized by incubating the leaf extract of A. glabra (2 mL) with AgN03 solution (l mM, 20 mL) for 3 hours. The formed AgNPs were separated using centrifugation (6000 rpm, 20 minutes) and the separated AgNPs were freeze dried. AgNPs were Characterized by UV — visible Spectrometer, particle size analyzer and scanning electron microscopy. acute toxicity tests against D. magna were conducted according to the Organization for Economic Co-operation and Development (OECD) standard procedure using neonates aged less than 24 hours reproduced using parthenogenesis. D. magna neonates were exposed to solutions within the concentration range Of 0.01 — 10 mg/L Of AgNP solutions and concentration range Of 0.5 — 2 gg/L Of ion solutions for 48 hours. Tests were conducted in quadruplicate and 95% confidence interval was calculated. Biosynthesized AgNPs showed a plasmon resonance peak at 419 nm, were spherical in shape and the size ranged between 10 — 190 nm. The EC50 value against D. magna for Agt ions were 1.41 ± 0.2 gg/L and for AgNPs it was 3.96 ± 1.1 mg/L after 48 hours. Results obtained from this study suggests that the toxicity ofbiosynthetic A. glabra - AgNPs exerts lesser toxic effect to D. magna than the Agt ions.
