Author ORCID Identifier

https://orcid.org/0000-0001-7406-6246

Date of Award

9-5-2025

Document Type

Thesis

School

School of Chemical & Biotechnology

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.Arvind Sivasubramanian

Keywords

Citrus Waste, Prosopis Juliflora, Halosarcia Indica, Sustainable Process, Antimicrobial Activity

Abstract

Agri-food industries produce large quantities of fruit waste which are usually discarded and one such major beverage juice waste is Citrus waste. Likewise, invasive plants like Prosopis juliflora, which is richly distributed across Tamil Nadu, are underutilized for secondary metabolites/bioactives isolation. Halophytes are another rich source of bioactives present around mangrove forests and distributed in the salt rich marshy land.

  1. Separation of phenylpropanoids from the Citrus waste through solvent extraction and pH-assisted precipitation was developed. The PPCM precipitated (phenylpropanoids form Citrus medica) were analysed by HPTLC and were found to contain Rutin, Naringin, Quercetin-3-beta-glycoside, Chlorogenic acid, Ferulic acid and optimization for these phenylpropanoids was further done with Box-Behnken assisted Response Surface Methodology. Further the optimized PPCM was used for the synthesis of AgNPs. AgNPs synthesis was further optimized with RSM and characterized by spectroscopic techniques. Antibacterial and antibiofilm inhibition studies revealed that the PPCM@AgNPs were efficient against P. aeruginosa bacterial biofilm inhibition, reduced bacterial burden in an in vivo zebrafish model and were non-toxic as seen by Histopathology and enzyme studies.

  2. The heartwood of Prosopis juliflora ethanol extract was found to harbour saponins and phenolics and the presence of saponin (Daucosterol) and flavonoids were confirmed with extraction followed by column chromatography. Separation of Daucosterol was achieved with solvent/antisolvent extraction and precipitation. Hydrotropic solubilisation of the remaining extract lead to the separation of Vitexin. Box-Behnken based RSM optimization methods were used and Vitexin was further utilized for the fabrication of silver nanoparticles and antimicrobial studies revealed the antibacterial and antibiofilm activity on MRSA. The zebrafish infection model and toxicity studies confirmed the bacterial inhibition and safety.

  3. The presence of hydroxycinnamic acids in Halosarcia indica was confirmed with aqueous extraction and column chromatography. A salt solution-based extraction of hydroxycinnamic acids from the Halosarcia indica (HCH) was developed and was further optimized through RSM optimization. HCH capped silver nanoparticles were synthesized along with RSM optimization studies. The antibacterial studies and biofilm inhibition confirmed the biofilm inhibition efficacy. Further evaluation in an in vivo zebrafish infection model demonstrated the bacterial burden reduction and the non-toxic nature of the biogenic nanoparticles was corroborated and confirmed with histopathological studies.

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