Flavonoid biosynthesis in tomato fruit cuticles after in vivo incorporation of H‐phenylalanine precursor

Radiolabelling of epicuticular waxes and cutin of isolated tomato fruit cuticles were determined after fruit surface application of H‐phenylalanine precursor. During fruit ripening, the precursor is incorporated in different phenolic components: the flavanone naringenin was found to be the major compound in the epicuticular waxes, while the amount of the labelled flavonoid in the cutin matrix was progressively increased throughout fruit ripening. Confocal microscopy, together with experimental estimation of the mobility (diffusion coefficient, D) and affinity (partition coefficient, K) of the flavonoids naringenin and chalconaringenin for the different cuticular components, indicate that these compounds are extruded to the outer surface of tomato fruits, forming molecular clusters.