Antibacterial, Antifungal, and Antioxidant Activities of Silver Nanoparticles Biosynthesized from Bauhinia tomentosa Linn

Senthil Renganathan; Sugunakala Subramaniyan; Nivetha Karunanithi; Preethi Vasanthakumar; Arne Kutzner; Pok-Son Kim; Klaus Heese

doi:10.3390/antiox10121959

Antibacterial, Antifungal, and Antioxidant Activities of Silver Nanoparticles Biosynthesized from Bauhinia tomentosa Linn

Antioxidants (Basel). 2021 Dec 7;10(12):1959. doi: 10.3390/antiox10121959.

Authors

Senthil Renganathan¹, Sugunakala Subramaniyan², Nivetha Karunanithi³, Preethi Vasanthakumar⁴, Arne Kutzner⁵, Pok-Son Kim⁶, Klaus Heese⁷

Affiliations

¹ Department of Bioinformatics, Marudupandiyar College, Thanjavur 613-403, India.
² Department of Bioinformatics, A.V.C. College, Mayiladuthurai 609-305, India.
³ Department of Biotechnology, A.V.C. College, Mayiladuthurai 609-305, India.
⁴ Department of Biotechnology, Bharath College of Science and Management, Thanjavur 613-005, India.
⁵ Department of Information Systems, College of Engineering, Hanyang University, 222 Wangsimni-ro, Seoul 133-791, Korea.
⁶ Department of Mathematics, Kookmin University, 77 Jeongneung-ro, Seoul 136-702, Korea.
⁷ Graduate School of Biomedical Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seoul 133-791, Korea.

Abstract

The biogenic synthesis of silver nanoparticles (AgNPs) has a wide range of applications in the pharmaceutical industry. Here, we synthesized AgNPs using the aqueous flower extract of Bauhinia tomentosa Linn. Formation of AgNPs was observed using ultraviolet-visible light spectrophotometry at different time intervals. Maximum absorption was observed after 4 h at 420 nm due to the reduction of Ag⁺ to Ag⁰. The stabilizing activity of functional groups was identified by Fourier-transform infrared spectroscopy. Size and surface morphology were also analyzed using scanning electron microscopy. The present study revealed the AgNPs were spherical in form with a diameter of 32 nm. The face-centered cubic structure of AgNPs was indexed using X-ray powder diffraction with peaks at 2θ = 37°, 49°, 63°, and 76° (corresponding to the planes of silver 111, 200, 220, 311), respectively. Energy-dispersive X-ray spectroscopy revealed that pure reduced silver (Ag⁰) was the major constituent (59.08%). Antimicrobial analyses showed that the biosynthesized AgNPs possess increased antibacterial activity (against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), with larger zone formation against S. aureus (9.25 mm) compared with that of E. coli (6.75 mm)) and antifungal activity (against Aspergillus flavus and Candida albican (with superior inhibition against A. flavus (zone of inhibition: 7 mm) compared with C. albicans (zone of inhibition: 5.75 mm)). Inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was found to be dose-dependent with half-maximal inhibitory concentration (IC₅₀) values of 56.77 μg/mL and 43.03 μg/mL for AgNPs and ascorbic acid (control), respectively, thus confirming that silver nanoparticles have greater antioxidant activity than ascorbic acid. Molecular docking was used to determine the mode of antimicrobial interaction of our biosynthesized B. tomentosa Linn flower-powder extract-derived AgNPs. The biogenic AgNPs preferred hydrophobic contacts to inhibit bacterial and fungal sustainability with reducing antioxidant properties, suggesting that biogenic AgNPs can serve as effective medicinal agents.

Keywords: antioxidant; bauhinia tomentosa; free radicals; microbial; nanoparticle; reactive oxygen species (ROS); silver.