Reduction of Acetylcholinesterase Inhibition Activity of Antiscolic Herbal Compounds by Bacilli Probiotics

Abstract

Antiscolic herbal compounds (AHCs) are fast-growing biopesticides but must be removed afterwards from harvested crops due to their potential toxicities towards animal acetylcholine esterase (AchE). In this work, we investigated the inhibitory effect of several typical AHCs on AchE as well as their detoxification by bacilli probiotics, another group of green agricultural additives. Results showed the AchE inhibition activity of studied AHCs follows an order of berberine (IC50 = 12.16 μmol/L) > osthole (233.21 μmol/L) ≈ matrine (262.41 μmol/L) >> trigonelline (no inhibition). Molecular simulation predicted that berberine, matrine and osthole combine with AchE preferentially in the catalytic channel for acetylcholine (Trp84 and His440), but forming more stable complexes. At the IC50 dosage, the addition of Bacillus subtilis (106~107 CFU/mL) or several other bacilli species detoxified osthole from 50% AchE inhibition to around 30%. Slight detoxification of matrine was also observed but the toxicity of berberine was not influenced after incubated with bacilli probiotics. Conversely, the three AHCs could completely inhibited the growth of B. subtilis following an order of berberine (0.15 mmol/L) > Matrine (9 mmol/) > osthole (1.5 mmol/L). B. subtilis Ruizhen@ exhibited stronger tolerance to AHCs than other commercial strains. Among other tested species, B. mucilaginosus was less sensitive than B. subtilis while B. laterosporus and P. polymyxa were resistant to AHCs. The potential antagonistic actions between AHCs and bacilli probiotics maybe useful in removal of residual herbal toxicity with green bacterial sweeper.