To 4 g material, 40 g of 0.1 M NaOH (1:10 solid-to-solvent ratio) was added in a 100 ml Erlenmeyer flask. Flasks with the extraction mixture were placed in a water bath at
25 or 60◦C and shaken at 110 rpm for 1 h. The mixtures were subsequently transferred
to 50 ml centrifuge tubes and centrifuged at 1520 × g for 20 min. The extracts and freeze-dried residues were stored at −18◦C until analysis. All experiments were performed in duplicate.