Supercritical CO2 extraction of naringenin from Mexican oregano (Lippia graveolens): its antioxidant capacity under simulated gastrointestinal digestion.

A supercritical CO2 method was optimized to recover naringenin-rich extract from Mexican oregano (Lippia graveolens), a flavanone with high antioxidant and anti-inflammatory activity. The effect of the extraction parameters like pressure, temperature, and co-solvent on naringenin concentration was evaluated. We used response surface methodology to optimize the naringenin extraction from oregano; the chemical composition by UPLC-MS of the optimized extract and the effect of simulated gastrointestinal digestion on its antioxidant capacity and total phenolic content were also evaluated. The optimum conditions were 58.4 °C and 12.46% co-solvent (ethanol), with a pressure of 166 bar, obtaining a naringenin content of 46.59 mg/g extract. Also, supercritical optimized extracts yielded high quantities of cirsimaritin, quercetin, phloridzin, apigenin, and luteolin. The results indicated that the naringenin-rich extract obtained at optimized conditions had higher total phenolic content, antioxidant capacity by TEAC and ORAC, and flavonoid content, compared with the methanolic extract, and the simulated gastrointestinal digestion reduced all these values.

Soluble melanins of the Randia echinocarpa fruit - Structural characteristics and toxicity.

The water-soluble melanins (SM) of Randia echinocarpa fruit possess interesting biological activities and have been scarcely characterized. In this study, SM were obtained at boiling (SMBT) and room (SMRT) temperatures and characterized by UV-Vis, IR, thermogravimetric analysis, and GC-MS of the hydrolysis products of the SM; besides, the solid-state 13 C NMR, elemental analysis, and acute and sub-acute toxicity of the SMBT were determined. SMBT and SMRT contain organic acids and carbohydrates and their spectroscopic signals and thermograms were similar, but the SMBT yield was higher. The SMBT were characterized by their elemental composition (C 48.260 ± 0.011%, N 3.693 ± 0.009% and H 6.093 ± 0.076%) consistent with the presence of aromatic rings and eumelanins, degradation temperature at 300°C, 13 C NMR signals supporting melanin-bonding with carbohydrates and organic acids, and innocuity in Balb/C mice (acute assay, LD50  > 5 g/kg b.w.; sub-acute assay, no lethality at 500 mg/kg b.w. for 30 days). PRACTICAL APPLICATIONS: The consumption of melanins has been associated with health benefits because of their biological activities (e.g., antioxidant, immunostimulatory, UV- and radiation-protective). Randia echinocarpa is employed in Mexican traditional medicine against chronic degenerative diseases (e.g., cancer and diabetes) and ailments of organs (e.g., kidney and lung) and systems (e.g., circulatory and gastrointestinal). The R. echinocarpa fruit contains water-soluble melanins (SM) that inhibit carbohydrate-digestive enzymes and show high antioxidant activity; thus, SM could be useful for the prevention and treatment of diabetes. This study showed that the SM structure contains melanin-bonding organic acids and carbohydrates, which could be associated with the SM solubility and higher yield, and that SMBT were innocuous in the acute and sub-acute assays in mice. Thus, the R. echinocarpa SMBT could be used as safe potential ingredients to develop functional products.