NON-LINEAR PARAMETER ESTIMATION OF ACETYLCHOLINESTERASE INHIBITION BY FREE AND NANOENCAPSULATED BERBERINE

Berberine is an isoquinoline alkaloid found in plants of the Euphorbiaceae, Ranunculaceae, and Papaveraceae families and also found in the roots of Berberis species, such as B. vulgaris. Although presenting remarkable bioactivity, berberine shows a poor aqueous solubility that may impact membrane permeability and bioavailability, thus nanoencapsulation by solid dispersion is proposed. Among the pharmacological activities already documented for berberine is the treatment of neurodegenerative diseases, such as Alzheimer’s disease (AD). The cholinergic hypothesis is one of the most accepted theories to understand the causes of AD, linking it to the deficiency in brain acetylcholine levels. The understanding of the kinetic mechanism and the reactions between berberine and acetylcholinesterase is of key importance to develop safe and optimized therapeutic applications. Thus in this work, a hybrid optimization method combining particle swarm optimization (PSO) and Gauss–Newton algorithms (Spyder (4.2.5) with Python (3.8)) was applied to the acetylcholinesterase inhibition kinetic data. The kinetic data of acetylcholinesterase hydrolysis of acetylthiocoline (without inhibitors) was evaluated for the estimation of Km (8970 ≤ 32520 ≤ 79030 nmol/L) and Vmax (8250 ≤ 10590 ≤ 13260 nM ASCh/min/U). With these parameters, a model discrimination strategy was applied for both inhibitors (free and berberine solid dispersion) showing that the best description of the experimental data was found for the non-competitive mixed model. The kinetic constants found for free berberine were, Kic: 100 ≤ 190 ≤ 450 nmol/L; Kiu: 220 ≤ 460 ≤ 1100 nmol/L; a: 0.67 ≤ 0.92 ≤ 1.20 (dimensionless factor affecting Vmax). In the case of berberine solid dispersion, Kic: 100 ≤ 190 ≤ 430 nmol/L; Kiu: 420 ≤ 760 ≤ 1730 nmol/L; a: 0.78 ≤ 0.96 ≤ 1.17. Thus, it can be concluded that the inhibition kinetic modeling pointed in the direction that the action of free and solid dispersion berberine is explained by a non-competitive mixed model, with Kiu > Kic, a result that indicates predominantly competitive inhibition.