Green Synthesis of Silver Nanoparticles From Pineapple (Ananas Comosus) Peel Extract: Physical-chemical Characterization and in Vitro Biological Activities

Abstract The objective of this work was to synthesize, characterize and evaluate silver nanoparticles (AgNPs) obtained from the aqueous extract of pineapple peel. After optimizing the synthesis of AgNPs, colloidal solutions of AgNPs showed maximum absorbance around 460 nm. The AgNPs in the final concentration of 1, 3 and 5 mmol L -1 showed average values of Z-average of 142.3, 127.0, 135.6 and, 153.2, 117.0 131.8 synthesized by water bath and ultrasound, respectively. Regarding PdI, all AgNPs showed low to moderate polydispersity. Zeta potential values ranged from -21.4 to -10.1. Images obtained by TEM for AgNPs prepared both by the water bath method and by the ultrasound method show particles with predominantly spherical morphologies, smooth and irregular edges. The synthesized AgNPs showed higher concentrations of total phenolic compounds (159.92 to 326.9 mg AG 100 g -1 ) when compared to the aqueous extract of pineapple peel (132.0 mg AG 100 g -1 ). The pineapple peel extract showed a higher ABTS radical inhibition value (88.16%) in relation to the value referring to AgNPs (19.11% to 77.90%). By the iron reduction method (FRAP), it was verified that the ability of AgNPs to reduce Fe 3+ to Fe 2+ was greater (4.49 to 6.83 mM of FeSO 4 for 10% solution) than that of the aqueous extract of the bark of pineapple (3.72 mM FeSO 4 for 10% solution). The AgNPs synthesized from the aqueous extract of pineapple peel were effective against Gram-negative bacteria E. coli and Pseudomonas aeruginosa and against Gram-positive bacteria S. aureus . The MIC varied between 2.6 and 21.25 mg.mL -1 for Gram-negative bacteria and from 21.25 to 42.25 mg.mL -1 for Gram-positive bacteria, pointing to Gram-negative bacteria as being the bacteria more susceptible to inhibitory and bactericidal actions after exposure to AgNPs. The results of the present study infer that the AgNPs obtained by water bath or ultrasound, regardless of the concentration, showed significant cytotoxic activity when tested in human breast cancer cells of the MCF-7 lineage and B16F10 murine melanoma cancer cells. IC50 values were similar for AgNPs obtained from different energy sources (water bath or ultrasound), but with the same AgNO3 concentration, indicating that there is no difference between using AgNPs obtained by water bath or ultrasound. These results suggest that the AgNPs synthesized from the aqueous extract of pineapple peel have potential and can be used in several areas, mainly in biomedical applications.