Screening Indigenous Medicinal Plants of Northeast India for Their Anti-Alzheimer’s Properties

Introduction: Alzheimer’s disease (AD) is a progressive neurologic disease of the brain that affects intellectual abilities, reasoning and memory. Acetylcholine (ACh) is involved in the maintenance of cognitive process. Pathologically, ACh production is compromised in the brains of AD affected people. Presence of acetylcholinesterase (AChE) in the synaptic cleft, which hydrolyzes ACh, further decreases the ACh-levels, and thereby, additionally compromises cognition. The tribal people of North East India have been using indigenous plants as traditional medicine for brain disorders. We assayed whether the plants used in the traditional tribal knowledge for the treatment of brain disorders might contain better AChE-inhibitors. Methods: We collected 10 traditional medicinal plants from Northeast India. A total of 39 plant extracts were prepared using three solvent systems. The Acetylcholinesterase (AChE) activity was measured with Ellman method. The experiment was done in triplicate for each level of inhibitor. The activity was measured at 412 nm wavelength using Plate Reader. The standard student t-test was used to show significant difference in IC₅₀ values between extracts. Results: The result are reported based on Km, Vmax, IC₅₀ (μg/μl), percentage inhibition and inhibition pattern. Two extracts had competitive inhibition, 11 extracts had mixed inhibition, 2 extracts had non-competitive inhibition, 11 extracts had uncompetitive inhibition and 4 extracts did not provide any proper pattern. The IC₅₀ for these plant extracts were at the range of 0.51-12.4 μg/μl. Notably, Cinnamomum camphora (leaf: chloroform), Litsea glutinosa (stem; chloroform), and Litsea glutinosa (stem; methanol) showed IC50 values of 0.51, 0.53 & 0.81 μg/μl, respectively.