Synthesis and characterization of specialized plant metabolites (SPMs)-loaded nanoparticles and evaluation of their bioactivity

The concept of "green chemistry" for "sustainable development" has been extensively studied in the last decade. Choosing a green or environmentally friendly solvent, a suitable non-toxic reducing agent and a safe substance for stabilization are undoubtedly the three most important prerequisites for the synthesis of green nanoparticles (NPs). Plants contain a variety of unique compounds, also known as specialized metabolites or phytochemicals, in their different organs. These compounds have gained a lot of attention based on their beneficial capability for both health and environment. Indeed, they can be exploited in the NPs synthesis process and accelerate its kinetics. This thesis begins with a comprehensive review of the recent trends in green nanotechnology, highlighting the role of phytochemicals in developing green nanoparticles, by employing eco-friendly and sustainable approaches. These methodologies meet the fundamental criteria of resilient technologies by eliminating the need of toxic solvents, expensive extraction and harsh synthesis protocols. The insights acquired from the literature review provided the conceptual foundation for the subsequent experimental studies. The first two experimental chapters demonstrate the detailed phytochemical profile of Ziziphus jujube Mill. and Camellia japonica plants. To acquire an in-depth comprehension of plant organ diversity and their biological activities, attributed to specific plant section were precisely investigated. Both species were selected based on their annual biomass production. Each collected plant part were separated and underwent ultrasound assisted maceration followed by Gel permeation chromatography (GPC) using Amberlite XAD-4 resin to achieve pure extract fractions. The extracts were preliminary investigated using spectroscopic (ATR FT IR, and UV-Vis) techniques, and then profiled by means of Ultra-High-Performance Liquid Chromatography-High-Resolution Mass Spectrometry (UHPLC-HRMS). In order to assess biological efficacy, extract from Ziziphus Jujube were examined for antiviral activity and showed quantifiable suppression against viral replication, whereas extract from Camellia japonica were tested for apoptosis induction and exhibited notable pro-apoptotic effects in leukemic cell lines. These findings validated the biomedical potential of both plants. Systematic comparison of phytochemical composition, biological efficacy and biomass yields underscored Camellia japonica flower as optimal candidate for synthesis of nanoparticles. The single, homogeneous organ simplifies experimental handling and reduces variability as compared to diverse plant parts. Furthermore, while Ziziphus dupes are frequently consumed and have been investigated for their nutritional and medicinal properties, Camellia japonica flowers are primarily used for ornamental purpose. This underutilised position, together with widespread availability makes Camellia japonica as novel choice. Subsequently, the Camellia japonica extract was employed to synthesize Silver nanoparticles (AgNPs), with polyphenols serving as well-known reducing and capping agents. UV-Vis and ATR-FTIR spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to characterise the synthesised nanoparticles. Given that metallic nanoparticles' cytotoxicity is still a key concern and high doses limits its versatility for biomedical applications, thus combining it with other therapeutic agents to develop dual therapies was considered. Therefore, PONI-C11-TMA polymer, was combined with AgNPs to develop nanoassemblies for antibacterial activity against E. coli and A. baumannii (Gram-negative bacteria). The checkerboard assay and fractional inhibition concentration index showed an additive effect for designed nanoassemblies. This thesis promotes a sustainable approach to design nanomedicine, by leveraging plant biomass and underexplored species. It emphasises the circular economy concepts and contributes to resilient living technologies by integrating green nanotechnology and industrial perspective, illustrating how sustainable utilisation of resources can boost both scientific innovation and human well-being.