Evaluation of Antioxidant and Cholinesterase Inhibitory Activities of Various Extracts of Cassia spectabilis

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that mainly occurs in elderly people. The increasing number of people suffering from AD causes health, social and economic problems. Therapeutic strategies implemented to slow down the progress of AD are by using cholinesterase inhibitors and antioxidants. The current study aimed to investigate the antioxidant and cholinesterase inhibitory properties of the leaves and stems of Cassia spectabilis as well as to determine the total phenolic contents in the samples. The leaves and stems of C. spectabilis were extracted with 96% ethanol by the maceration method. The cholinesterase inhibitory assay was performed by using the modified Ellman’s method against two cholinesterase enzymes, namely acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The antioxidant properties of the samples were evaluated using 2,2-diphenyl-1-picryl hydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods. The total phenolic contents (TPC) were determined by a colorimetric assay using gallic acid as a reference. The results showed that the leaves and stems of C. spectabilis exerted significant inhibitory effects against both AChE and BChE enzymes with IC₅₀ values of 24.3 and 9.8 µg/mL for the leaves and 58.6 and 47.8 µg/mL for the stems, respectively. The extracts showed moderate antioxidant activity in both DPPH and ABTS assays with IC₅₀ ranging from 117 – 313 µg/mL. The presence of phenolic content in the samples may contribute to the antioxidant potency of the samples. The presence of non-phenolic compounds, such as alkaloids may be responsible for the cholinesterase inhibitory properties of the extracts.