In vitro antioxidant, anticholinesterase inhibitory, and antimicrobial activity studies of Terminalia chebula (Retz) and Terminalia arjuna (Roxb)

Ethanol extracts of Terminalia chebula and Terminalia arjuna were studied for the determination of phytochemical constituents, in vitro antioxidant, anticholinesterase, inhibitory, and antimicrobial activities. Results of phytochemical analysis showed that T. arjuna has significant phenolic and flavonoid contents (108.2 mg PEs/mg extract and 74.2 mg QEs/mg extract) respectively. T. chebula also showed good phenolic contents 113.4 mg PEs/mg extract and low value of flavonoids contents 8.91 QEs/mg extract correspondingly. The antioxidant activity was performed using three complementary assays, including lipid peroxidation inhibitory, metal chelating, and reducing power assays. The acetylcholinesterase assay was performed according to Ellman's method spectrophotometrically. The antibacterial and antifungal activity, however, was determined by the disc and well diffusion methods. Terminalia arjuna exhibited higher lipid peroxidation inhibitory activity (IC50: 57.7 ± 3.7 μg/mL), higher reducing power (A0.5: 0.63 ± 0.4 mg/mL), and higher metal chelating activity (IC50: 115 ± 5.01 μg/mL) that Terminalia arjuna. Both Terminalia species indicated high acetylcholinesterase inhibitory activity (IC50: 29.6 ± 3.9 and 29.7 ± 0.5 μg/mL, respectively). Promising antibacterial activity was recorded for Terminalia chebula (72.44 % and 60.0 %) against Bacillus sp. and Staphylococcus species with MIC values of 5.0 mg/mL and 2.5 mg/mL, respectively. Similarly, Terminalia arjuna (72.41 % and 63.33 %) revealed activity against Bacillus sp. and Staphylococcus species with MIC values of 2.5 mg/mL and 5.0 mg/mL. However, all the tested fungal strains were resistible to both species. In conclusion, Terminalia arjuna and Terminalia chebula may be significant sources of potential new acetylcholinesterase inhibitors, which could be utilized to treat Alzheimer's disease. The plants are also recommended for further studies to isolate antimicrobial agents and lipid peroxidation inhibitors.