Building Blocks of the Protective Suberin Plant Polymer Self-Assemble into Lamellar Structures with Antibacterial...

The protection of terrestrial plants from desiccation, mechanical injury, and pathogenic invasion is achieved by waxes and cutin polyesters on leaf and fruit surfaces as well as suberin polymers that are embedded in the cell walls of roots, but the physicochemical principles governing the organization of these biological composites remain incompletely understood. Despite the well-established enzymatic mediation of suberin formation in the skins of potato tubers, cork oak trees, and internal plant tissues, the additional possibility of self-assembly in this system was suggested by our serendipitous finding that solvent extracts from potato phellem tissues form suspended fibers and needles in the absence of such catalysts over a period of several weeks. In the current study, we investigated self-assembly for three-component model chemical mixtures comprised of a hydroxyfatty acid, glycerol, and either of two hydroxycinnamic acids that together typify the building blocks of potato suberin biopolymers. We demonstrate that these mixtures spontaneously form lamellar structures that are reminiscent of suberized plant tissues, incorporate all constituents into self-assemblies, can form covalently bound ester structures, and display antibacterial activity. These findings provide new perspectives on the self-association and reactivity of these classes of organic compounds, insights into agriculturally important suberin formation in food crops, and a starting point for engineering sustainable materials with antimicrobial capabilities.