Silver Nanoparticles and Polyphenol Inclusion Compounds Composites for Phytophthora cinnamomi Mycelial Growth Inhibition

Abstract

Phytophthora cinnamomi, responsible for “root rot” or “dieback” plant disease, causes a significant amount of economic and environmental impact. In this work, the fungicide action of nanocomposites based on silver nanoparticles and polyphenol inclusion compounds, which feature enhanced bioavailability and water solubility, was assayed for the control of this soil-borne water mold. Inclusion compounds were prepared by an aqueous two-phase system separation method through extraction, either in an hydroalcoholic solution with chitosan oligomers (COS) or in a choline chloride:urea:glycerol deep eutectic solvent (DES). The new inclusion compounds were synthesized from stevioside and various polyphenols (gallic acid, silymarin, ferulic acid and curcumin), in a [6:1] ratio in the COS medium and in a [3:1] ratio in the DES medium, respectively. Their in vitro response against Phytophthora cinnamomi isolate MYC43 (at concentrations of 125, 250 and 500 µg·mL−1) was tested, which found a significant mycelial growth inhibition, particularly high for the composites prepared using DES. Therefore, these nanocomposites hold promise as an alternative to fosetyl-Al and metalaxyl conventional systemic fungicides.

In Vitro Antifungal Activity of Chitosan-Polyphenol Conjugates against Phytophthora cinnamomi

“…The in vitro tests led to notable differences in the inhibition of mycelium growth of P. cinnamomi, observing a superior performance of the preparations based on ferulic acid with AgNPs and silymarin without AgNPs (thus evidencing that the addition of AgNPs, in spite of their antimicrobial [14] at different concentrations (in µg·mL −1 ). For each treatment, concentrations labelled with the different lowercase letters are significantly different at p < 0.05 by Tukey's test.…”

“…It should be clarified that the antifungal efficacy assays reported herein and those reported in Matei et al [14] (focused on the comparison between two dispersion media and on differences between polyphenols, but with AgNPs in all cases) were run in parallel. Since they were conducted at the same time and in the same conditions, the impact of physiological changes of the fungus or differences in abiotic conditions may be excluded.…”

“…Data from the results obtained herein and from those reported in a previous study with AgNPs [14] were subjected to analysis of variance (ANOVA), followed by post hoc comparison of means through Tukey's HSD (honest significant difference) test at p < 0.05. SPSS Statistics v.25 software (IBM; Armonk, NY, USA) was used.…”

“…Microwave-assisted aqueous biphasic system separation was used to prepare the polyphenol inclusion compounds. The conjugates with chitosan oligomers in hydroalcoholic solution medium were prepared according to the procedure previously reported in Matei et al [14], and were characterized by infrared spectroscopy (FTIR), SEM and TEM microscopy techniques to ensure the reproducibility of the results presented in patent P201731489 [15].…”

Estudio de la actividad antifúngica in vitro de materiales compuestos basados en complejos de inclusión de polifenoles contra Phytophthora cinnamomi

“…Los procedimientos para la preparación de compuestos de inclusión de polifenoles, mediante separación en un sistema bifásico acuoso asistida por microondas, y para la preparación de los compuestos con oligómeros de quitosano en solución hidroalcohólica fueron los mismos que los referidos previamente en Matei, et al [7], asegurando así la comparabilidad de los resultados.…”