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After cellulose, lignin is the most abundant plant-derived polymer in nature. It provides mechanical support to plants, but it has also a defense role against pests and diseases, thanks to antioxidant, bactericidal, and antifungal properties, deriving from its polyphenolic nature. Huge quantities of technical lignins are obtained during several industrial processes and they actually represent a waste of paper pulp and bioethanol industry. Although in the last decades many efforts have been directed to obtain lignin valorization in several fields and for diverse applications, this biobased polymer is still largely underutilized. In particular, very little is known about the possibility to exploit its antioxidant, antifungal, and antibacterial properties in the agronomical field. On the other hand, pest control is often achieved by using copper-based pesticides, but environmental and health issues urge for novel solutions implying reduced copper content. We here describe novel hybrid organic–inorganic materials obtained by combining copper­(II) salts with two types of technical lignins. Cu-containing materials (lignin@Cu) have been characterized by different techniques, including X-ray powder diffraction and transmission electron spectroscopy analyses, revealing nanocrystals of brochantite (Cu4SO4(OH)6) grown in the lignin matrix. Lignin@Cu was tested for its antifungal and antibacterial profile against a vast panel of pathogens of agronomical interest. Furthermore, preliminary tests on crops in a greenhouse were performed: lignin@Cu had better performances than a commercial pesticide based on copper­(II) hydroxide on tomato plants against Rhizoctonia solani, indicating a great potential of these materials as plant protection products.

Oligolignans present in substantial amounts in Norway spruce and Scots pine knots were characterised. The hydrophilic knotwood substances were extracted and different chromatographic methods were applied to obtain fractions for analysis by GC, GC-MS, HR-EI-MS, LC-ESI-MS, NMR, and FTIR. b-O-4-Linked guaiacylglyceryl ethers of hydroxymatairesinol (Ia, Ib, Ic), secoisolariciresinol (II), lariciresinol (III), isolariciresinol (IV), lignan A (V), liovil (VI), conidendrin (VII), and pinoresinol (VIII) were identified in the spruce knotwood extract and b-O-4-linked guaiacylglyceryl ethers of nortrachelogenin (IX) and secoisolariciresinol (II) in the pine knotwood extract. The structures of allo-hydroxymatairesinol-49-guaiacylglyceryl ether (Ia), hydroxymatairesinol-4-guaiacylglyceryl ether (Ib), hydroxymatairesinol-49-guaiacylglyceryl ether (Ic), secoisolariciresisinol-4-guaiacylglyceryl ether (II), and lariciresinol-49-guaiacylglyceryl ether (III) were determined via GC-MS, HR-MS, and 1 H and 13 C NMR analyses. The structures of (Ia), (Ic), (IV), (V), (VI), (VII), and (IX) have not been reported earlier. Spruce stemwood, both heartwood and sapwood, also contained oligolignans in small amounts. In addition, some dilignans with four phenylpropanoid units were tentatively identified in the hydrophilic knotwood substances.

Despite its high chemical value, most of lignin is nowadays burnt as low value fuel. It is therefore important to find innovative applications for its use. Copper compounds are used as plant protection products for more than 50 different diseases in viticulture, arable crops, hops, and horticulture, and they have been used for more than 100 years. Minimization of copper in agriculture has become a fundamental issue due to its negative environmental impact. Here we present a series of hybrid organic−inorganic materials (lignin@Cu), deriving from the combination of lignin with brochantite, Cu 4 (OH) 6 SO 4 . Optimization of the synthetic procedures has allowed us to isolate lignin-based materials containing different percentages of copper, where the brochantite crystals are featured by different morphologies and dimensions. A more environmentally safe synthesis of lignin@Cu materials by mechanochemistry is also investigated, which reduces the amount of water used and makes easier and faster the isolation of the final materials. Tests on strawberry and tomato plants in a greenhouse have highlighted a significative efficacy of the lignin@Cu materials against different pathogens at a copper content much lower than the one of copperbased commercial pesticides. A crystal morphology−activity correlation is also traced out. The synergic activity of lignin and copper ions can be used to reduce the copper content for efficient pathogen control. Moreover, the mechanochemical approach ensures a greener synthetic approach, in a perspective of a more sustainable agriculture.