Occurrence and characterisation of calcium oxalate crystals in stems and fruits of Hylocereus costaricensis and Selenicereus megalanthus (Cactaceae: Hylocereeae)

摘要

Detailed description about occurrence of calcium oxalate (CaOx) crystals in the edible vine cactus speciesHylocereus costaricensis and Selenicereus megalanthus is scarce. Therefore, we evaluated and characterizedthe presence, morphology and composition of CaOx crystals in both species. Crystals were isolated fromgreenhouse and in vitro vegetative stems, and from ripe fruit peels and pulp by enzymatic digestionand density centrifugation and quantified with a haemocytometer. Morphologies were studied usingscanning electron microscopy, elemental composition with energy-dispersive X-ray spectroscopy andsalt composition withX-ray powder diffraction.Analyses conducted confirmed thatisolated crystals wereexclusively composed by CaOx, both mono- and dihydrated. Highest crystal contents were measured ingreenhouse stems, followed by the fruit peels. While very few crystals were quantified in in vitro plants,they were not detected in the fruit pulp at all, which is of advantage for its human consumption andcould be linked to mechanisms of seed dispersal through animals. Different crystal morphologies wereobserved, sometimes varying between genotypes and tissues analysed. This is the first work known tothe authors with a detailed characterization of CaOx crystals in vine cacti.