Abstract
In this study, we investigated the antioxidant and anti-inflammatory phytochemicals and paramagnetic species in dragon fruit using high-performance liquid chromatography (HPLC) and electron paramagnetic resonance (EPR). HPLC analysis demonstrated that dragon fruit is enriched with bioactive phytochemicals, with significant variations between each part of the fruit. Anthocyanins namely, cyanidin 3-glucoside, delphinidin 3-glucoside, and pelargonidin 3-glucoside were detected in the dragon fruit peel and fresh red pulp. Epicatechin gallate, epigallocatechin, caffeine, and gallic acid were found in the dragon fruit seed. Additionally, 25–100 mg × L−1 of dragon fruit pulp and peel extracts containing enrichment of cyanidin 3-glucoside were found to inhibit the production of reactive oxygen species (ROS), reactive nitrogen species (RNS), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in cell-based studies without exerted cytotoxicity. EPR primarily detected two paramagnetic species in the red samples. These two different radical species were assigned as stable radicals and Mn2+ (paramagnetic species) based on the g-values and hyperfine components. In addition, the broad EPR line width of the white peel can be correlated to a unique moiety in dragon fruit. Our EPR and HPLC results provide new insight regarding the phytochemicals and related stable intermediates found in various parts of dragon fruit. Thus, we suggest here that there is the potential to use dragon fruit peel, which contains anthocyanins, as a natural active pharmaceutical ingredient.
Highlights
Dragon fruit (Hylocereus sp.), commonly known as pitaya or pitahaya, is a member of the cactus family Cactaceae [1]
Both red and white pulp seed were found to have significantly greater phenolic and flavonoid contents than the other parts (p < 0.05), which is similar to the findings of the study of Nguyen et al [18], who reported on the total phenolic compounds in the seed and pulp of red and white dragon fruits
Cyanidin, and delphinidin are anthocyanin compounds found in the peel of the red dragon fruit (H. polyrhizus) using liquid chromatography-mass spectrometry (LC-MS) assay [21]
Summary
Dragon fruit (Hylocereus sp.), commonly known as pitaya or pitahaya, is a member of the cactus family Cactaceae [1]. Much remains unknown about the paramagnetic species (Mn2+, antioxidative organic radicals, etc.) present in dragon fruits and their antioxidant and anti-inflammatory activities. The magnetic-field position and relative intensities of the EPR lines occur between the energy levels of electrons with unpaired spins. There are no reports describing the distribution of antioxidative phytochemicals and related intermediates in dragon fruits. In this investigation, the paramagnetic species in each part of the dragon fruit were examined using EPR and antioxidative phytochemicals were analyzed HPLC. The EPR technique measured two types of paramagnetic species in dragon fruits, which displayed antioxidative effects. The EPR line widths and phytochemical activities of various parts of the dragon fruit were discussed
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