Green-synthesized Silver Nanogels from Delonix elata and Delonix regia: Antimicrobial Efficacy Comparison of Ethanolic, Hexane, and Hydroalcoholic Extracts
Sakshi, Ajay Kumar Singh RawatIntroduction:
The increasing prevalence of multidrug-resistant microorganisms has intensified the search for novel antimicrobial agents, particularly from botanical sources. Nanotechnology offers promising strategies for drug delivery, and silver nanogels have demonstrated potent antimicrobial properties. This study aims to synthesize silver nanogels using extracts of Delonix elata and Delonix regia and to comparatively evaluate their antimicrobial activity. Specifically, the objective is to assess the antimicrobial efficacy of silver nanogels fabricated from ethanolic, hexane, and hydroalcoholic extracts of different plant parts (seeds, bark, and leaves) against selected microbial strains.
Methods:
Seeds, bark, and leaves of Delonix elata and Delonix regia were extracted using ethanol, hexane, and hydroalcoholic solvents. These extracts were utilized for the synthesis of silver nanogels. The antimicrobial activity of the prepared nanogels was evaluated against Bacillus subtilis (MTCC 441), Escherichia coli (MTCC 1573), and Pseudomonas aeruginosa (MTCC 424) using the cup plate method. Ciprofloxacin and norfloxacin were used as standard reference antibiotics. Zones of inhibition were measured at concentrations ranging from 20-100 μg/mL to determine comparative efficacy.
results:
Nanogels prepared using hydroalcoholic and hexane extracts showed the highest zones of inhibition as compared to ethanolic extracts amongst the various extracts used. The nanogel of the barks and leaves especially that of Delonix regia exhibited the best antimicrobial activity with maximum 13 mm zone of inhibition registered around 100 ug /ml. Although conventional drugs exhibited more inhibition potential, there were a number of nanogel samples having similar activity on increased dosing.
Results:
Silver nanogels prepared using hydroalcoholic and hexane extracts exhibited significantly higher antimicrobial activity compared to ethanolic extracts. Among the different plant parts, bark- and leaf-derived nanogels, particularly from Delonix regia, demonstrated the highest activity, with a maximum zone of inhibition of 13 mm observed at 100 μg/mL. Although standard antibiotics showed superior antimicrobial effects, several nanogel formulations exhibited comparable activity at higher concentrations.
Discussion:
The findings indicate that plant-based silver nanogels possess considerable antibacterial potential against tested pathogens. Enhanced efficacy may be attributed to improved extraction of bioactive phytochemicals in hydroalcoholic and hexane solvents, along with improved diffusion and sustained release characteristics of nanogels. Statistical analysis (mean ± SD and significance testing) supports the reliability of the results. These observations are consistent with recent literature and highlight the potential of nanoformulations as alternative or adjunct antimicrobial strategies against drug-resistant microorganisms.
Conclusion:
The study concludes that silver nanogels synthesized from Delonix elata and Delonix regia exhibit promising antibacterial activity. The type of extract and plant part significantly influence the efficacy of the formulation. These findings contribute to the advancement of plant-based nanogel systems as potential antimicrobial alternatives.