Exploring the Therapeutic Potential of Premna obtusifolia and Oxalis corniculata: A Combined in Vitro Bioassay and Molecular Docking Study

Background: Premna obtusifolia (Lamiaceae) and Oxalis corniculata L. (Oxalidaceae) are two ethnomedicinal plants widely used in Bangladesh for the management of infections and inflammatory disorders. Although they belong to distinct botanical families and differ chemically, P. obtusifolia being rich in diterpenoids and O. corniculata abundant in flavonoids, both are traditionally associated with antioxidant and antimicrobial effects. The present study comparatively evaluated their methanolic extracts and solvent fractions using DPPH radical scavenging assay, total phenolic content (TPC) determination, and disc diffusion antimicrobial screening. Materials and Methods: After powdering the leaves and extracting them with methanol, the fractions were separated into n-hexane and chloroform. Using the DPPH radical scavenging experiment, antioxidant activity was evaluated, and IC50 values were computed. This was done using the disc diffusion method to measure antimicrobial activity. To determine the total phenolic content (TPC), the Folin–Ciocalteu technique was employed. To provide mechanistic insight, previously reported 14 phytochemicals from these species were subjected to molecular docking against human carbonyl reductase 1 (CBR-1; PDB ID: 4Z3D) and Staphylococcus aureus dihydrofolate reductase (DHFR; PDB ID: 2W9S). Results: The crude methanolic extract of P. obtusifolia showed an IC50 of 31 µg/mL, while O. corniculata exhibited stronger antioxidant activity (IC50 = 15.61 µg/mL). Both extracts demonstrated significant antimicrobial effects, whereas n-hexane and chloroform fractions showed moderate antimicrobial activity. The antioxidant potential of P. obtusifolia and O. corniculata was correlated with TPC values of 185.82 mg GAE/g and 154.90 mg GAE/g, respectively. Diosmetin-7-O-β-D-glucopyranoside, Quercetin, Arucadiol, and Swertisin demonstrated binding affinities comparable to reference ligands under the same docking conditions, according to molecular docking, indicating their potential as antioxidants and antimicrobials. Conclusion: The substantial antibacterial and antioxidant properties of the crude methanolic extracts support the traditional usage of Oxalis corniculata and Premna obtusifolia and suggest that these plants may be used as natural sources of bioactive chemicals for medicinal purposes.