Cutin composition of selected northern berries and seeds

Monomeric compositions of the extractive-free cuticular polymer fractions of seven berries – rosehip (Rosa rugosa), black chokeberry (Aronia melanocarpa), strawberry (Fragaria x ananassa), raspberry (Rubus idaeus), cloudberry (Rubus chamaemorus), crowberry (Empetrum nigrum) and rowanberry (Sorbus aucuparia) – as well as the seeds from three berries – cloudberry, sea buckthorn (Hippophaë rhamnoides) and blackcurrant (Ribes nigrum) – were investigated. Depolymerisation of the cutin polymer was carried out using NaOMe-catalysed methanolysis and the composition of TMS-derivatised monomers was determined by GC using FID and MS detection. Two depolymerisation techniques were compared; 1.0 M NaOMe at ambient temperature and 1.3 M NaOMe under reflux conditions. The degree of depolymerisation of the cuticular membrane ranged from 2% (strawberry) to 84% (rosehip) for the CHCl3-soluble cutin monomers. Depolymerisation of seed samples was low (1–3%). The predominant monomers were C16 and C18 ω-hydroxy acids with mid-chain functionalities, mainly epoxy and hydroxy groups, but suberin-like α,ω-dicarboxylic acids, with mid-chain hydroxyl groups and C15 chain length monomers, were also found. Seed cutin monomers differed from the corresponding berry skin monomers.