Among fruits, the apple is unique for producing large amounts of the dihydrochalcone phloridzin, which, together with phloretin, its aglycone, is valuable to the pharmaceutical and food industries for its antidiabetic, antioxidant, and anticarcinogenic properties, as well as its use as a sweetener. We analysed the phloridzin concentration, total phenolic content, and antioxidant activity in the peel, flesh, seeds, juice, and pomace of 13 international and local apple varieties. In the unprocessed fruit, the seeds had the highest phloridzin content, while the highest total phenolic contents were mostly found in the peel. In processed samples, phloridzin and the total phenolic compounds especially were higher mostly in juice than in pomace. Moreover, the total phenolic content was much higher than the phloridzin content. Juice showed the highest antioxidant activity, followed by the peel and flesh. Across all samples, antioxidant activity did not directly correlate with phloridzin concentrations, suggesting that the antioxidant activity ascribed to phloridzin may need re-evaluation. In the Ferric Reducing Antioxidant Power (FRAP) assay, phloridzin only showed antioxidant activity at high concentrations when compared to its aglycone, phloretin. Considering the large amounts of apple juice produced by the juice industry, residual pomace is a promising source of phloridzin. For technical use, processing this phloridzin to phloretin would be advantageous.

The production of valuable bioactive compounds in the medicinal plant Glycyrrhiza glabra L. (G. glabra) would benefit from biotechnological approaches for the cultivation and induction of metabolite-producing hairy roots. Germination trials were tested to overcome seed dormancy, achieving high germination rates with sulfuric acid treatment. Hairy root cultures of cotyledons using Rhizobium rhizogenes strain 1724 showed the highest transformation efficiency. A fast-growing line, line S, was subsequently exposed to light treatments (red, blue, and blue and red combined) to evaluate their effects on growth, phenolic content, and Ferric Reducing Antioxidant Power (FRAP). Hairy root cultures grown in blue light and in blue and red light combined had higher growth rates than those grown in red light only or in control conditions (dark). FRAP increased over time under all light treatments, including the control, and those cultures exposed to blue and red light combined had higher FRAP than the control. These findings provide valuable insights into conditions for optimal seed germination and hairy root transformation. Treatment of the line S with different qualities of light induced changes in antioxidant capacity and phenolic content, indicating promise for its use in upregulating secondary metabolite production in G. glabra for future biotechnological applications.

β-Glucosidases (βGLs) play important roles in plant secondary metabolism by hydrolyzing glycosylated compounds involved in defense, signaling, and the formation of bioactive and flavor-related metabolites. In this study, a β-glucosidase from Fragaria × ananassa (Fra-βGL; FxaC_10g48920.t1) was identified and biochemically characterized in comparison with a commercial β-glucosidase from Prunus dulcis (Pru-βGL). The Fra-βGL cDNA was cloned and heterologously expressed in Escherichia coli, and the recombinant protein was purified for biochemical characterization. Substrate screening demonstrated that Fra-βGL hydrolyzed the 7-O-glucosides of quercetin, kaempferol, and luteolin, whereas no detectable activity was observed toward the tested 3-O-glucosides, anthocyanin glucosides, arbutin, or phloridzin under the assay conditions. Kinetic analysis revealed higher catalytic efficiencies of Fra-βGL than Pru-βGL toward all four substrates examined. Fra-βGL showed its highest turnover rate and catalytic efficiency toward the synthetic substrate p-nitrophenyl-β-D-glucopyranoside (pNP-Glc), with a K_cat of 60.33 s⁻¹ and a K_cat/K_m of 10.18 mM⁻¹·s⁻¹. Among the naturally occurring flavonoid glucosides, Fra-βGL exhibited the highest catalytic efficiency toward quercetin 7-O-glucoside (4.14 mM⁻¹·s⁻¹), approximately fivefold higher than that of Pru-βGL (0.824 mM⁻¹·s⁻¹). Thermal stability analysis showed progressive loss of activity with increasing temperature, with Pru-βGL retaining greater residual activity than Fra-βGL at elevated temperatures. Molecular docking suggested structural features that may contribute to the observed preference of Fra-βGL for flavonoid 7-O-glucosides over the corresponding 3-O-glucosides. Collectively, these findings demonstrate the substrate selectivity and distinct catalytic properties of Fra-βGL and identify Fra-βGL as a candidate for further investigation in the context of flavonoid glycoside metabolism in strawberry.