Produtos Naturais como Fontes de Compostos Biotecnológicos e Terapêuticos

Abstract

This thesis investigated natural products as sources of biotechnological and therapeutic innovation in two studies. In the first study, the total water-soluble fraction of kefir (WSF) and its <10 kDa fraction were used for the green synthesis of silver nanoparticles (AgNPs). The WSF-AgNPs exhibited an absorbance peak at 470 nm, a negative zeta potential (-30 mV), and a broad hydrodynamic size distribution (500-1000 nm). AgNPs derived from the <10 kDa fraction showed predominantly smaller particles (50-200 nm), although with lower stability. The WSF-AgNPs inhibited multidrug-resistant bacteria, with MIC values of 25 μg/mL for Acinetobacter baumannii and 50 μg/mL for Klebsiella pneumoniae, showing bactericidal activity at the minimum inhibitory concentrations. In Drosophila melanogaster, larval exposure to 100 μg/mL impaired developmental parameters, whereas no robust changes in 15-day adult survival were observed, despite subtle signs of redox imbalance, suggesting a dose- and stage-dependent safety window. In the second study, ethanolic and acetonic extracts of Saskatoon berry (Amelanchier alnifolia) were characterized by LC-MS/MS and in silico analyses, indicating solvent-dependent composition and potential interactions with targets associated with Alzheimer’s disease. The acetonic extract showed higher total phenolic content and strong antioxidant performance. In cellular models, it exhibited low cytotoxicity and a neuroprotective effect under beta-amyloid peptide challenge. In D. melanogaster, supplementation with both extracts increased longevity in healthy flies and, in the AD-like model driven by GMR-GAL4, the acetonic extract reduced beta-amyloid burden and preserved retinal thickness and structure, with a tendency toward dose- and sex-dependent responses. Together, these findings support the potential of fermented matrices and polyphenol-rich fruits as promising sources of candidates for antimicrobial and neuroprotective applications.