Sweet chestnut standardized fractions from sustainable circular process and green tea extract: In vitro inhibitory activity against phytopathogenic fungi for innovative applications in green agriculture.

Annalisa Romani,Lorenzo Moncini,Roberta Bernini,Margherita Campo,Gabriele Simone,Vijai Gupta

doi:10.1371/journal.pone.0247298

Abstract

In the present study, the antifungal activities of two commercial tannins-rich dry fractions towards different filamentous fungi of agronomical and food interest were evaluated. In particular, a standardized fraction from sweet chestnut (Castanea sativa Mill.) wood by-products and a commercial green tea (Camellia sinensis L.) leaf extract were tested at different concentrations (0.1-5.0% and 0.2% w/v respectively). The Sweet Chestnut Wood fraction was produced in an industrial plant through an environmentally and economically sustainable process, involving hot-water extraction and a sequence of membrane filtration steps with different molecular cut-offs for fractionation and concentration of the active principles. The Sweet Chestnut Wood and Green Tea Leaf extracts were characterised via HPLC/DAD/MS quali-quantitative analysis. The first extract showed a polyphenolic content of 20.5% w/w, 100% hydrolysable tannins; the second one showed a polyphenolic content of 87.5% w/w, of which 96.2% epigallocatechin gallate and 3.8% epicatechin gallate. The antifungal activity of the Sweet Chestnut fraction in aqueous solutions was evaluated towards different filamentous fungi, in particular telluric phytopathogens (Fusarium oxysporum f. sp. radicis-lycopersici; Fusarium solani; Rhizoctonia solani; Sclerotium rolfsii) and post harvest pathogens (Botrytis cinerea, that can also attack field plants; Penicillium digitatum; Penicillium italicum), and compared to the activity of Green Tea Leaf extract solutions. The experimental results evidenced, for almost all tested fungi, inhibition of the mycelial growth rate in presence of tannins. The lowest inhibitions were observed for B. cinerea (7.5%, to 28.9%) and P. italicum (53.8% in 5.0% w/v Sweet Chestnut extract substrate). A proportional inhibitory effect to tannin concentration was observed for F. oxysporum f. sp. radicis-lycopersici and F. solani (from 33.7% to 56.6%), R. solani (from 29.7% to 68.8%) and P. digitatum (64.7% to 87.0%). The highest effect resulted for S. rolfsii, (5.0% to 100%).

Highlights

In the recent years, the European legislation aimed to strongly reduce the impact of agricultural practices on environment and on health and wellness of operators and consumers
The results show a better efficacy of Sweet Chestnut Wood (SCW) extract compared with GTL extract against the Fusarium and Sclerotium
This paper describes for the first time the activity of SCW fraction and GTL extract on pathogenic fungi of agronomic interest

Summary

Introduction

The European legislation aimed to strongly reduce the impact of agricultural practices on environment and on health and wellness of operators and consumers. Community new Directives and Regulations, gradually implemented by specific Legislative Decrees at national level, imposed the revision of all criteria and rules for the production, market and use of active substances and products for plant protection in the European Union This led to a progressive reduction of use and doses of traditional chemicals and products, limiting or prohibiting the diffusion of the most harmful substances, and discouraging the use of traditional pesticides in favour of sustainable agriculture practices with low environmental impact and minimal or negligible risk for the health of operators and users of the finished products. Some of them can be responsible for intoxications and allergic disorders due the production of mycotoxins and allergens To counteract these pathogens, synthetic fungicides are necessary but the negative side effects of their use, including their toxicity, are relevant on both human health and environment. In consideration of the increasing attention devoted to develop sustainable and eco-friendly processes in crop production, plant extracts, mainly those rich in tannins and other polyphenolic compounds, could represent a valid solution as an alternative to synthetic fungicides [2]

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Conclusion