Comparative in-vitro study on phytochemical profile, antioxidants, and antimicrobial activities of Pogostemon benghalensis leaves and stem from two different geographical regions at Lumbini Province of Nepal

Pogostemon benghalensis stem and leaves have been investigated for their phytochemical constituents, antioxidant and antibacterial activities. For this study, P. benghalensis was collected from two different geographical region of Lumbini Province of Nepal. The extraction was carried out by the triple cold maceration process using methanol and ethyl acetate. The quantitative determination of total phenol content (TPC) was accomplished by Folin-Ciocalteau and the highest TPC value was obtained from the leaf Terai of methanolic extract 132.78 ± 1.45 GAE/g and total flavonoid contents (TFC) was accomplished by aluminium chloride colorimetric assay and the highest TFC value was obtained from stem Terai extract 599.75 ± 0.82 mg QE/g. The antioxidant activity of the extract was tested using scavenging activity of 1, 1-diphenyl-2- picrylhydrazyl (DPPH) radical method and the highest antioxidant activity was obtained by stem Terai methanol extract with an IC50 value of 7.46 µg/mL when compared with antioxidant activity of ascorbic acid (IC50 = 6.72 µg/mL) as standard. To evaluate their antibacterial properties against the Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, the disc diffusion method was used and showed that the stem of Terai methanol extract has the highest zone of inhibition (ZOI) (14.15 ± 3.14 mm) against P. aeruginosa. This study thus suggests that the leaf and stem of Terai plant species have great pharmacological importance since they have potent biological activities. Key words: Geographical region, Folin-Ciocalteau, 1, 1-diphenyl-2- picrylhydrazyl (DPPH), colorimetric assay, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, disc diffusion method.