Obtaınıng of gold nanopartıcles from haucl4 and crocus sativus by green-synthesıs: Characterızatıon, potentıal antımıcrobıal and antıoxıdant effects

Herbal medicines have been the foundation of traditional treatments for centuries and continue to be an important source of health for millions of people today. However, limitations such as low bioavailability and stability reduce the effectiveness of these natural compounds. Nanovesicular systems like liposomes, niosomes, and solid lipid nanoparticles offer promising solutions to overcome these issues and enable targeted drug delivery. Crocus sativus (saffron) demonstrates anti-inflammatory, antioxidant, and therapeutic properties with its bioactive compounds such as safranal, picrocrocin, crocin, and crocetin. In addition to its widespread use in the food industry for color, aroma, and flavor, it is also regarded as a valuable natural source in medical research. Nanotechnology has led to significant advancements in drug delivery and diagnostic fields; however, challenges such as biocompatibility, toxicity, high cost, and regulatory uncertainty still present difficulties in clinical applications. Gold nanoparticles (AuNPs) attract attention with their biocompatible and antibacterial properties; they promote the production of reactive oxygen species, causing damage to cellular structures and leading to bacterial eradication. This activity is further enhanced as the particle size decreases. This study aims to investigate the characterization, antimicrobial activities, and antioxidant capacities of AuNPs synthesized using extracts from the bulbs, leaves, and spice of Crocus sativus, grown in Amasya. The study grouped the samples into eight categories: aqueous extracts of bulb (S) and leaf (Y), aqueous (BS) and ethanol (BE) extracts of the spice, and AuNPs coated with these extracts (bulb (SAuNP), leaf (YAuNP), spice aqueous extract (BSAuNP), and spice ethanol extract (BEAuNP)). After optimization, characterization was carried out using XRD, FTIR, and SEM analysis. Subsequently, antimicrobial activity tests were performed using pathogens including Aspergillus niger and Candida utilis fungi, Listeria monocytogenes, methicillin-resistant Staphylococcus aureus, Streptococcus agalactiae gram positive bacteria, Salmonella paratyphi, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii, Campylobacter jejuni bacteria, and Neisseria meningitidis bacteria. Additionally, antibiotic synergy with tetracycline antibiotic discs was evaluated to determine the antimicrobial effects of the extracts in combination with the antibiotic. The antioxidant capacities of the samples (DPPH, ABTS, FRAP) as well as their phenolic and flavonoid contents were also determined. The strongest antimicrobial activity was observed in the BS-AuNP extract at a 10% concentration, with a 32.48 mm zone of inhibition against A. niger. The highest antimicrobial activity in antibiotic combinations was found in the BE extract at a 20% concentration, with a 32.2 mm zone of inhibition against MRSA. The lowest antimicrobial activity was observed in the Y-AuNP antibiotic combination, with a 7.6 mm zone of inhibition. According to antioxidant capacity results, the highest value in the DPPH assay was found in the BS sample (0.280 µg Trolox Equiv./µL). The highest value in the ABTS assay was found in the Y sample (2.420 µg Trolox Equiv./µL). In the FRAP assay, the highest value was found in the Y sample (1.147 µg Trolox Equiv./µL). In terms of total phenolic and flavonoid content, the highest phenolic content was found in the Y sample (0.552 µg Gallic Acid Equiv./µL), while the highest flavonoid content was found in the BS extract (2.330 µg Quercetin Equiv./µL). This study demonstrates that extracts from different parts of Crocus sativus exhibit strong antioxidant capacities, but antimicrobial efficacy alone is limited. However, when combined with antibiotics, this efficacy significantly increases.