Ex vivo antiacetylcholinesterase studies on silver nanoparticles synthesized using green approach

Abstract

For the green fabrication of silver nanoparticles (AgNPs), scientists are favoring herbal sources to avoid the toxic effects of synthetic sources. Thus, in this study, the AgNPs were generated using the herbal extract of the whole plant Hippeastrum hybridum L. (HH) and 1 mM AgNO3 aqueous solution. These HH‐AgNPs were characterized via UV–Vis Spectroscopy, which showed a maximum absorbance of 1.61 at a 432 nm sharp peak; FT‐R analysis, which confirmed the functional groups in HH extract and their AgNPs; XRD analysis, which gives 4‐Bragg's reflections at 2θ and confirmed the HH‐AgNPs crystal structure with 13.3 nm average size; SEM analysis, which confirmed the irregular‐shaped morphology with 40 nm mean size; and EDX analysis, which confirmed the elemental composition and reported that Ag was present in 22.75%. After characterization, these AgNPs were tested as anti‐Alzheimer agents against acetylcholinesterase (AChE) in ex vivo activity using rat brain homogenate as a source of AChE enzyme. AChE showed 48 ± 0.03 and 42 ± 0.05% activity at 150 μg concentration of HH plant and HH‐AgNPs, respectively, with 145 ± 0.24 and 124.2 ± 0.14 μg IC50 concentration. According to enzyme kinetics results, the plant extract inhibits AChE in competitive mode (Km increased from 166.2% to 1,379.2% and Vmax not affected), while HH‐AgNPs showed the mixed mode of inhibition (Km increased from 0.029 to 0.048, and Vmax decreased from 9 to 5.4). KIapp and Vmaxiapp were also calculated (KIapp increased from 39 to 95.1 μg, and Vmaxiapp remained constant for the plant), while for HH‐AgNPs, both Kmaxipp and Vmaxiapp increased from 122.32 to 325 μg and 8.15 to 9.8 μg, respectively. The Km, Ki, and KI were also calculated and were found to be 0.017 mM (HH‐plant) and 0.2 mM (HH‐AgNPs); 98 μg (HH‐plant); and 129 μg (HH‐AgNPs), 53 μg (HH‐plant), and 179 μg (HH‐AgNPs), respectively. γKm (18 mM) was calculated for HH‐AgNPs, while for HH‐plant, it is not applicable. In conclusion, it could be said that HH‐plant plays a significant role in the generation of small‐size HH‐AgNPs. These AgNPs exhibited significant anti‐AChE potential as compared to HH‐plant extract and proved to be an herbal source for the treatment of AD.