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**79**

**Chapter 5**

**Abstract**

**1. Introduction**

Agriculture

Hydrolysable Tannins in

*Matteo Cerboneschi and Enrica Bargiacchi*

*Sergio Miele, Stefania Tegli, Carlos Garcia Izquierdo,* 

Hydrolysable tannins, water-extracted from sweet chestnut (*Castanea sativa* Mill.)

(CHT) and membrane concentrated, have several effects as antioxidant, antimicrobial, and metal complexing agents. Some patents described their use as nitrogen release modulators and iron complexing agent to fight plant chlorosis and to control legume seed-borne disease and nitrosamine and mycotoxin during plant and food processing. Biostimulating activity of raw CHT, placed near seed or transplant seedlings, was assessed on early plant growth (starter effect) and found related to earlier production of a larger plant fine root mass, with greater P early uptake. Increased resistance to nematodes, with CHT applications on tobacco, was investigated. Recent process stream fractioning permitted to identify some CHT fractions with antimicrobial and antioxidant effects which were tested for their potential in promoting selected aspects of plant yield, quality, and protection and maintaining and improving feed and food quality during processing. EU Life+2013 Evergreen found a method of application of a CHT fraction to protect tobacco and carrot plants in nematodeinfested fields. A protective effect of CHT on some bacterial diseases of olive tree and kiwi was disclosed. Environmental and soil toxicities were also investigated finding

very low impacts and the possibility to reduce Cu use in agriculture.

**Keywords:** plant biostimulant, hydroculture, gall nematodes, TSNA, mycotoxins

Polyphenols, a complex group of phytochemicals derived from phenylalanine, are characterized by an aromatic ring with a reactive hydroxyl group. They include phenolic acid derivatives, called hydrolysable tannins (HTs). They present a carbohydrate molecule (generally ∂-glucose), esterified at various levels with gallic or ellagic acids. These gallotannins and ellagitannins are hydrolyzed by weak acids or bases and are more prone to oxidation than condensed tannins (CTs) which are characteristics of oak wood and grapeseed extracts. Most HTs are typical of Mediterranean plants, but only tannins from water-extracted sweet chestnut (*Castanea sativa* Mill.) biomass (CHT) have been industrially exploited in agriculture as a corrective, a fertilizer chemistry modifier, and/or a biostimulant product, with a protective activity against nematodes and some microbial strains. Another important agricultural use, as a feed ingredient, is in expansion [1], while some technological applications in food processing and supplement production are just at their beginning [2, 3]. Other Mediterranean HTs "competitors" of CHT, i.e., those
