Effects of heat degradation of betanin in red beetroot (Beta vulgaris L.) on biological activity and antioxidant capacity

Opuntia stricta (Haw.) Fruit Pulp and Seeds as Source of Bioactive Phytochemicals with Promising Functional Properties

In recent years, Opuntia stricta (Cactaceae family) has garnered considerable attention due to its promising nutritional and medicinal properties. This study aims to investigate the chemical composition and bioactivity of Sicilian Opuntia stricta fruit pulp and seeds. Liquid chromatography-mass spectrometry analysis revealed the presence of betalain derivatives, especially isobetanin and betanin, as the main pigments in the freeze-dried pulp and its hydroalcoholic extract. Other constituents, namely, piscidic acid, isorhamnetin-3-O-glucoside, and isorhamnetin-3-O-rutinoside, were identified. Linoleic acid (41.95%) was the main abundant fatty acid followed by palmitic acid (19.32%) in the seed's fixed oil as analyzed by gas chromatography-mass spectrometry. The antioxidant activity was assessed using a multi-target approach using 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power assay (FRAP), and β-carotene bleaching tests. The ABTS test showed greater sensitivity to the action of the samples with significant half-maximal inhibitory concentrations (IC50) of 13.24 and 14.82 mg/mL for the hydroalcoholic extract and the freeze-dried fruit pulp, respectively. Opuntia stricta's extracts were also assessed for the carbohydrate-hydrolyzing enzyme and lipase inhibitory effect. The freeze-dried fruit pulp exhibited the highest effect against lipase (IC50 of 33.54 μg/mL). Collectively, our results contribute to the characterization of this traditionally consumed Sicilian edible plant and suggest its use as a source of bioactive compounds useful for the prevention of obesity linked to hyperglycemia.

DPPH Measurements and Structure-Activity Relationship Studies on the Antioxidant Capacity of Phenols

The consumption of foods that are high in antioxidant capacity is believed to contribute to good health. Moreover, the addition of highly antioxidant compounds to foods is believed to prevent food deterioration. Among the known antioxidants in food, phenols have been identified as the primary antioxidants. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay is a simple, inexpensive, and rapid method widely used to evaluate the antioxidant capacity. Although the results of the DPPH assay depend on conditions such as the reaction time and concentration, the experimental conditions have not been standardized. Further, previous research that compared the antioxidant capacity determined through the DPPH assay largely focused on the differences in the specific substructures of approximately several dozen compounds. In this study, we conducted DPPH assays on 169 phenols under the same experimental conditions and summarized the correlation between their structures and activity. This DPPH assay study is the first single-laboratory investigation of the largest number of components in terms of their Trolox equivalent antioxidant capacities. Further, the analysis method was reproduced in an interlaboratory collaborative study, enabling its application in the reproduction and comparison of measurements in other laboratories.