Numerous underexplored plant species are believed to possess considerable potential in combating oxidative stress and its associated health impacts, emphasizing the need for a comprehensive methodological screening approach to assess their antioxidant capacity. This study investigated 375 plant extracts, utilizing both cell-free and cellular methods to evaluate their antioxidant properties. Target-based antioxidant capacity was evaluated by the total phenolic content (TPC) and ferric reducing antioxidant power (FRAP) assays. Cell-based assays employed the H₂DCF-DA probe to measure reactive oxygen species (ROS) levels and the Griess assay to quantify nitric oxide (NO) levels in stressed Caco-2 and RAW264.7 cells, respectively. The highest TPC and FRAP values were found in extracts of Origanum vulgare and Fragaria × ananassa leaves. Several plant extracts significantly reduced stress-induced ROS or NO levels by at least 30%. Distinctive selectivity was noted in certain extracts, favoring the significant reduction of NO (e.g., Helianthus tuberosus extract), of ROS (e.g., Prunus domestica subsp. Syriaca extract), or of both (e.g., Fragaria × ananassa leaf extract). A strong correlation between TPC and FRAP values and moderate correlations between the results of the cell-free and cell-based assays were evident. These findings highlight the great antioxidant potential of underexplored plant extracts and the diversity of the underlying mechanisms, emphasizing the importance of a multifaceted approach for a comprehensive assessment.

Plant extracts rich in phytochemicals are known for their health benefits. Plant extract library from edible plants obtained from the region of Upper Austria was prepared. Food grade extraction procedures were applied, and relevant physico-chemical parameters measured. A focus on polyphenolic compounds revealed a significant correlation between the total phenolic content (measured by a colorimetric assay) and the cumulated concentration of main individual polyphenols (measured by HPLC-DAD), demonstrating the comparability of these parameters. Targeted screening was performed by HPLC-FLD and -MS for the presence of phytomelatonin. 20 extracts were identified with concentrations of up to 1.4 µg/mL of this phytochemical, which attracts much attention from the food industry. Finally, chemometric methods were employed to cluster extracts based on their phenolic compound profile. This approach allows for an informed preselection of extracts without the need for comprehensive chemical analysis.

Background/Objectives: Individuals with special metabolic demands are at risk of deficiencies in fat-soluble vitamins, which can be counteracted via supplementation. Here, we tested the ability of micellization alone or in combination with selected natural plant extracts to increase the intestinal absorption and bioefficacy of fat-soluble vitamins. Methods: Micellated and nonmicellated vitamins D3 (cholecalciferol), D2 (ergocalciferol), E (alpha tocopheryl acetate), and K2 (menaquionone-7) were tested in intestinal Caco-2 or buccal TR146 cells in combination with curcuma (Curcuma longa), black pepper (Piper nigrum), or ginger (Zingiber officinale Roscoe) plant extracts. The vitamin uptake was quantified via HPLC-MS, and bioefficacy was assessed via gene expression analyses or the Griess assay for nitric oxide generation. Results: Micellization increased the uptake of vitamin D into buccal and intestinal cells, with vitamin D3 being more efficient than vitamin D2 in increasing the expression of genes involved in calcium transport. The micellization of vitamin E acetate increased its uptake and conversion into biologically active free vitamin E in intestinal cells only. The vitamin K2 uptake into buccal and intestinal cells was increased via micellization. Plant extracts increased the uptake of select micellated vitamins, with no plant extract being effective in combination with all vitamins. The curcuma extract increased the uptake of vitamins D2/D3 but not their bioefficacy. Black pepper and ginger extracts increased the uptake of vitamin E acetate into intestinal cells but failed to increase its conversion into free vitamin E. The ginger extract augmented the uptake of vitamin K2 and increased NO generation additively. Conclusions: Our data substantiate the positive effects of micellization on fat-soluble vitamin absorption and bioefficacy in vitro. While the application of plant extracts in addition to micellization to further increase bioefficacy is an interesting approach, further studies are warranted to understand vitamin-specific interactions and translation into increased bioefficacy.