Supercritical Carbon Dioxide Extraction of Bioactive Compounds from Feijoa (Feijoa sellowiana) Leaves

Biogenic Silver and Zero-Valent Iron Nanoparticles by Feijoa: Biosynthesis, Characterization, Cytotoxic, Antibacterial and Antioxidant Activities

Background: and Purpose:

Green nanotechnology is an interesting method for the synthesis of functional nanoparticles. Because of their wide application, they have set up great attention in recent years.

Objective:

The present research examines the green synthesis of Ag and zero-valent iron nanoparticles (AgNPs, ZVINPs) by Feijoa sellowiana fruit extract. In this synthesis, no stabilizers or surfactants were applied.

Methods:

Eco-friendly synthesis of Iron and biogenic synthesis of Ag nanoparticles were accomplished by controlling critical parameters such as concentration, incubation period and temperature. Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier-Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction analysis (XRD), Dynamic Light Scattering (DLS) and UV-Vis were applied to characterize NPs. The cytotoxicity of NPs was investigated in two cell lines, MCF-7 (breast cancer) and AGS (human gastric carcinoma). A high-performance liquid chromatography (HPLC) analysis was also performed for characterization of phenolic acids in the extract.

Results:

Both NPs displayed powerful anticancer activities against two tumor cell lines with little effect on BEAS-2B normal cells. Synthesized AgNPs and ZVINPs inhibited the growth of all selected bacteria. Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumonia, Staphylococcus aureus, Enterococcus faecalis, Acinetobacter baumannii and Escherichia coli have been studied in two stages. We initially examined the ATCCs followed by clinical strain isolation. Based on the results from resistant strains, we showed that nanoparticles were superior to conventional antibiotics. DPPH (diphenyl-1-picrylhydrazyl) free radical scavenging assay and iron chelating activity were used for the determination of antioxidant properties. Results showed a high antioxidant activity of scavenging free radicals for ZVINPs and powerful iron-chelating activity for AgNPs. Based on the HPLC data, catechin was the major phenolic compound in the extract.

Conclusion:

Our synthesized nanoparticles displayed potent cytotoxic, antibacterial and antioxidant activities.

Modified Supercritical Carbon Dioxide Extraction of Biologically Active Compounds from Feijoa Sellowiana Leaves

For the first time, the modified supercritical carbon dioxide extraction (MSCE) of biologically active compounds from Feijoa sellowiana leaves was investigated. Total yield (TY) and bioactivity of biocompounds in terms of DPPH• (%DPPHsc) and HO• (%HOsc) radicals scavenging were maximized via multivariate optimization. The optimized conditions were the pressure of 272.34 bar, supercritical carbon dioxide flow rate of 1.58 mL min−1, temperature of 52.48 °C, and dynamic extraction time of 110.62 min. The predicted values of the TY, %DPPHsc, and %HOsc were 81.12 mg g−1, 85.16 %, and 75.66 %, respectively. The chromatographic analysis demonstrated gallic acid as the main biophenolic (136.20 ± 0.16 mg g−1). The scanning electron microscopy images showed dramatic disruption of cells treated with MSCE. A comprehensive comparison was made between current findings and other techniques (conventional and ultrasonic waves assisted extraction). More TY was achieved using conventional method but the bioactivity of MSCE products was considerably better.