Kinetics of Acetylcholinesterase inhibition in Fasciolopsis buski and Raillietina echinobothrida by shoot extract of Alpinia nigra, an indigenous medicinal plant

Alpinia nigra (Geartn) Burtt. is a traditionally used medicinal plant, aqueous extract of which is consumed by the tribes of Tripura, India, against helminthiasis. In order to explore the effects of A. nigra plant extract on the neuromuscular activity of parasites, inhibition of acetylcholinesterase (AchE) in Raillietina echinobothrida and Fasciolopsis buski was investigated. The interaction of the enzyme with the substrate and the plant extract was characterized by the kinetic parameters K_m and V_max which were determined from Lineweaver-Burk plots. The ethanolic shoot-extract of A. nigra inhibited the AchE activity in dose-dependent manner with IC₅₀ values of 1.4 mg/ml and 0.91 mg/ml in R. echinobothrida and F. buski, respectively. K_m and V_max of R. echinobothrida and F. buski were found to be 1.23 mM, 1.45 µmole/h/mg proteins and 1.09 mM, 2.27 µmole/h/mg proteins, respectively. The interaction of plant extract reduced the V_max values by 33.10% and 31.28% while the K_m values were increased by 81.30% and 79.82% in R. echinobothrida and F. buski, respectively. Determination of the inhibitory parameters of A. nigra on AchE activity in R. echinobothrida and F. buski revealed that the plant extract acted as a mix and non-competitive type of enzyme inhibitor.