Antioxidant, Antibacterial Activity, In Silico Molecular Docking, and ADME-Toxicity Study of Lactone from Rhizome of Angiopteris helferiana

Abstract

Objective. The red rhizome of Angiopteris helferiana has been used widely to treat muscle fatigue, bone pain, and skin infection in Nepal. However, scientific evidence for its bioactive compounds and their bioactivities was lacking till January, 2024. Therefore, we investigated to validate and advance the further use and development. Methods. Column chromatography, including MCI gel CHP20P, Sephadex LH-20, ODS, and Silica gel, was used for the isolation of compounds from 70% methanol extract of A. helferiana rhizomes. The isolated compounds were evaluated for their TLC-based antioxidant and antibacterial activity against Staphylococcus aureus, Klebsiella pneumonia, Escherichia coli, and Pseudomonas aeruginosa by adopting the agar well diffusion protocol. Furthermore, in silico molecular docking against the penicillin binding protein of E. coli (PBP1b, PBP2, and PBP3 TPd) and ADME toxicity of the isolated compounds was predicted. Results and Discussion. Angiopteroside (1) and osmundalactone (2) were isolated for the first time from the red rhizomes of A. helferiana. The structure of the isolated compounds was elucidated on the basis of spectroscopic (1H-, 13C-, and 13C/DEPT-NMR) and spectrometric (LC MS/ESI and IR) analyses and comparison with reported literature. Both compounds were inactive towards DPPH scavenging activity. Compound 1 showed poor inhibitory activity against E. coli, with inhibition zone range of 2–7 mm. However, both isolated compounds were found to be resistant against S. aureus, K. pneumonia, and P. aeruginosa. Based on in silico molecular docking forecasting, compound 1 revealed the good binding affinity with PBP1b (−6.5 kcal/mol), PBP2 (−5.8 kcal/mol) and PBP3 TPd (−6.1 kcal/mol) compared to positive control meropenem with PBP1b (−6.6 kcal/mol), PBP2 (−6.9 kcal/mol), and PBP3 TPd (−6.6 kcal/mol). Similarly, compound 2 showed weak preference for PBP1b (−4.3 kcal/mol), PBP2 (−4.4 kcal/mol), and PBP TPd (−4.5 kcal/mol). Compounds 1 and 2 were predicted to be safe in terms of hepatotoxicity, cytotoxicity, mutagenicity, and carcinogenicity, with a potential to induce nephrotoxicity similar to that of meropenem. Conclusion. This study successfully isolates two lactones with antibacterial properties and inspires the researcher to further research, development, and formulation.