Micromorphological investigation on the leaves of the rock samphire (Crithmum maritimum L.): occurrence of hesperidin and diosmin crystals

A micromorphological study was carried out on Crithmum maritimum L. (rock samphire), a halophyte belonging to the Apiaceae and used in folk medicine. The study led to the finding of relevant amounts of two closely related flavonoids, namely diosmin and hesperidin, which attract increasing interest for their biological properties. Anatomical investigations of leaf tissue showed the presence of needle-shaped crystals forming plumose clusters, mainly located close to, or within, vascular bundles. Scanning electron microscopy (SEM) analysis provided a more detailed morphological characterization of crystals, while the absence of mineral elements in their composition was assessed by SEM-EDX. High performance liquid chromatography (HPLC) analysis of leaf tissue was conducted to detect hesperidin and diosmin and to quantify their amounts. SEM analysis of two Rutaceae plants rich in hesperidin and diosmin, i.e., Citrus limon and Barosma betulina, revealed the same plumose crystals found in C. maritimum, while in these plants the two flavonoids were also quantified by HPLC. The data clearly indicate the occurrence of hesperidin and diosmin crystals in C. maritimum leaves, thus providing a scientific basis for an exploitation of this plant in saline agriculture, as a crop or source of bioactive phytocompounds.