Antioxidant, anticholinesterase, and neurotrophic potentials of indigenous medicinal herbs of Bangladesh

In Ayurvedic system of medicine, a variety of medicinal herbs are being prescribed for brain disorders, including mental dysfunction, indifference, and memory impairment. Neuropharmacological mechanisms of these herbs are poorly understood. A total of nineteen indigenous medicinal herbs of Bangladesh were investigated for their neuropharmacological potentials, including antioxidant, anticholinesterase, and neurotrophic activities. The antioxidant activity of plant ethanolic extracts was determined based on their DPPH free radical scavenging capacity. Acetylcholinesterase (AChE) inhibitory activity was determined by the colorimetric assay based on Ellman's method. The neurotrophic activity of plant extracts was measured based on their capacity to promote neurite outgrowth in a primary culture of hippocampal neurons. Of the herbs, Camellia sinensis, Terminalia chebula, Cinnamomum tamala, Terminalia bellirica, Phyllanthus emblica, and Curcuma longa exhibited remarkable antioxidant activity with IC50 values of <100 µg/mL. The highest anticholinesterase activity was shown by C. longa (IC50 9.37 µg/mL) followed by C. sinensis (IC50 86.01 µg/mL) and C. tamala (IC50 86.37 µg/mL). Notably, C. tamala showed the highest neurotrophic activity (an increase in the length of primary neurites by 82% compared to control), whereas C. sinensis and C. longa showed moderate activities. The neurotrophic activity of C. tamala was reported for the first time. The present findings indicate that these indigenous herbs, particularly C. tamala, C. sinensis, and C. longa possess a remarkable neuropharmacological potential and suggest that these neuroactive herbs could be used in disease-modifying therapies for brain disorders.