2.2. Biological samples preparation

Suberin was extracted from cork using cholinium hexanoate [12] ([N₁₁₁C₂H₄OH][O₂CC₅H₁₁], water content ∼1.8%) as described before [13], (2 ​h, 100 ​°C, without stirring). After stopping the reaction by adding cold DMSO, the mixture was filtered (the insoluble residue recovered and washed) and suberin precipitated by adding water (4 ​°C) and recovered by centrifugation (4 ​°C, 1 ​h) at 2452 ​g for the parental sample or sequentially at 96, 385, 865, 1538, and 2452 ​g for the suberin centrifuged fractions. All samples were kept lyophilized (FreeZone 4.5 ​L −105 ​°C Benchtop Freeze Dryers, Labconco) under a controlled atmosphere until further use. Cork and cork residue were solubilized with the aid of cryogenic milling using a RESTCH Cryomill equipped with a 25 ​mL grinding jar with six zirconium oxide grinding balls (10 ​mm) (Supplementary Fig. S7).