Comparative GC/MS Analysis, Antioxidant and Anticholinesterase Study for the Alcoholic Extracts of Leaves, Flowers and Bark of Terminalia arjuna (Roxb)

Terminalia arjuna tree is an important plant with massive traditional uses. This study aims to carry out a comparative phytochemical and biological evaluation on the leaves, flowers, and bark of T. arjuna. Phytochemical analysis involved exploration of the methanolic extracts using GC/MS technique as well as quantitative determination of the phenolic and flavonoid contents using Folin–Ciocalteu and AlCl₃ reagents, respectively. In vitro biological evaluation of the different extracts as antioxidant and anticholinesterase were studied. Reducing power assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were used to evaluate the antioxidant activity while anticholinesterase activity of the extracts was measured by Ellman’s reagent at two concentrations, 10 and 100 μg/ml. Results revealed that the bark extract has the highest phenolic content 250.3 ± 17.3 mg/GAE/g dry sample, the leaves has the highest flavonoid content 5.03 ± 1.18 mg/RE/g dry sample. GC/MS results implied the identification of twenty-six, seventeen and five compounds in flowers, bark and leaves, respectively. Methyl palmitate (30.79%) and methyl oleate (17.73%) were the major compounds detected in the bark extract; while thymol (68.31%) and α-terpineol (15.75%) were the major compounds in leaves extract, finally thymol (23.78%) as well and p-cymene (17.78%) were the major constituents in the flower extract. Considering the antioxidant activity, all tested extracts showed somewhat similar results in both methods. The anticholinesterase activity showed that the bark extract exhibited the most significant activity at 10 μg/ml with an inhibition value of 23.75% ± 1.397. Anticholinesterase results come in agreement with the antioxidant and total phenolic content; therefore, a correlation between antioxidant potential of the plants and Alzheimer control could be concluded.