Obtenção, caracterização e aplicação de material a base de zinco via síntese verde utilizando extratos de Pfaffia glomerata

Abstract

In the green synthesis of zinc-based materials, extracts from different plant types or from distinct parts of the same plant—such as leaves, flowers, fruits, stems, and roots—can be used, obtained through conventional and non-conventional extraction methods. These materials have a wide range of applications, including wound dressings, pharmaceuticals, cosmetics, nanofibers, and polymeric membranes, due to their antimicrobial and antioxidant activities, absence of toxic solvents, and reduced processing time. The aim of this study was to synthesize and characterize a zinc-based material using aqueous extract from the aerial parts of Pfaffia glomerata and to apply this material in the functionalization of polymeric nanofibers (PVA), evaluating their antimicrobial and antitumoral activities. For extract preparation, solid samples (leaves, flowers, and stem) were mixed with water (1:20 m/v) and subjected to ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) for 5 min, and to conventional extraction (CE) for 60 min, at 40°C and 60°C. The synthesis of the zinc-based material was carried out using a 2:1 (v/v) ratio of extract to zinc nitrate (0.3 mol/L) at 70°C for 3 h, followed by drying at 70°C for 24 h and calcination at 500°C for 4 h. The leaf extracts from batches 1 and 2 (F1 and F2) obtained via UAE at 40°C presented the highest phenolic compound content (F1 = 594.514 µgGAE/mL_extract; F2 = 552.546 µgGAE/mL_extract) and the highest antioxidant activity (F1 = 0.798 µmolTrolox/mL_extract; F2 = 0.982 µmolTrolox/mL_extract) compared to the other extracts. The synthesis yield was higher for the leaf extracts (F1 = 0.607–1.168 mg_material/mL_nitrate; F2 = 0.481–0.889 mg_material/mL_nitrate) compared to flowers and stems. The material obtained under the best condition (U40AF1-SZ-E1) was identified as hydrated zinc nitrate hydroxide with a monoclinic structure. After calcination (U40AF1-C-E1), the XRD pattern showed sharper diffraction peaks, confirming a crystalline hexagonal ZnO phase (71%). The morphology of U40AF-C-E1 revealed irregular spherical agglomerates, with an average size of 0.82 ± 0.33 µm (3.68k×) and 0.92 ± 0.32 µm (4.38k×). The antimicrobial activity of U40AF1-SZ-E1 and U40AF1-C-E1 against E. coli and S. aureus was greater for the calcined material. The micro/nanoparticles were then incorporated into PVA nanofibers via electrospinning, resulting in three nanofiber types: pure PVA (N-BR), PVA functionalized with chemically synthesized ZnO (N-SQ), previously prepared by Costa (2018), and PVA functionalized with U40AF-C-E1 (N-SV). Compared to N-BR and N-SQ, N-SV exhibited greater ductility and flexibility, continuous nanofibers (0.18 ± 0.05 µm) with visible nanoparticles, improved antimicrobial performance against E. coli and S. aureus, good biocompatibility in NIH3T3 cells, and cytotoxic effects against HepG2 cells, indicating antitumoral potential. These findings highlight the potential of Pfaffia glomerata leaf extracts as reducing agents in the green synthesis of zinc-based materials, enabling their integration into functionalized polymeric nanofibers, which demonstrated bacteriostatic activity against pathogens and cytotoxic effects in tumor cells. Therefore, the main contribution of this study was to demonstrate the feasibility of producing micro/nanoparticles and functionalized nanofibers with biological properties and biomedical potential using non-conventional extraction techniques and without toxic solvents, through the use of Pfaffia glomerata leaf extract.