Metabolomic characterization of pitaya fruit from three red-skinned cultivars with different pulp colors

Pitaya is a new fruit crop, whose exotically colored fruits have excellent nutritional and antioxidant properties. In this study, the primary metabolite profiles of three pitaya cultivars i.e. 'Guanhuahong' (red peel with red pulp), 'Guanhuabai' (red peel with white pulp) and 'Guanhuahongfen' (red peel with pink pulp) were investigated using GC-MS and Ultraviolet-visible spectroscopy. In the fruit pulp, levels of starch, organic acids, and inositol decreased as the fruit matured. Glucose, fructose, sucrose and sorbitol contents increased gradually during fruit maturation and reached their highest levels in the pulp at the mature stage. Citramalic acid was identified for the first time in the pulp of Hylocereus species. Higher levels of total phenols, flavonoids and antioxidant activities were detected in the peel than in the pulp during fruit maturation of all three cultivars. The finding of higher levels of total phenols and flavonoids in the pitaya peel than in the pulp at the mature stage suggests that pitaya peels are a good source of natural phenols and flavonoids.