Common steviol glycosides standards kit

The extraction procedure and SG profile followed Zimmermann et al. (2012) [91 (link)]. SGs were estimated using a Jasco PU980 HPLC system (JASCO Benelux B.V., Utrecht, the Netherlands) coupled with a UV-visible wavelength detector. A hydrophilic column (Luna HILIC 200A, Phenomenex Inc., Torrance, CA, USA), 5 mm, 250 mm × 4.6 mm (Phenomenex Inc., Torrance, CA, USA), and the corresponding pre-column (4 × 3.0 mm) were used. The UV detection was performed at 205 nm at room temperature, with a flow rate of 0.68 mL/min and a run time of 20 min. Separation was carried out in acetonitrile/water (80:20) as an isocratic mobile phase at pH 3.6 regulated with acetic acid. Chromatograms were gathered online, and data were obtained using a Jasco interface (Hercules 2000 Interface Chromatography). The Common Steviol Glycosides Standards Kit was purchased from Chromadex (LGC Standards S.r.L., Milan, Italy). The calibration curves (0.005–1.00 g L⁻¹) were achieved from standard mixtures containing rubusoside, dulcoside A, stevioside, and rebaudioside A, C, D, E, and M (Reb A, C, D, E, and M), and SGs were quantified using authentic standards. Total SGs were determined as the sum of single SGs [44 (link)].

Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), fluorescein sodium salt, 2,2′-azobis [2 -methylpropionamide] dihydrochloride (AAPH), quercetin dihydrate, 2′-7′-dichlorodihydrofluorescin diacetate (DCFH-DA), were purchased from Sigma-Aldrich (Milan, Italy). Dulbecco’s Modified Eagle’s Medium (DMEM) high glucose culture media, penicillin, streptomycin, L-glutamine, trypan blue, trypsin, were from culture grade and also purchased from Sigma-Aldrich. Fetal bovine serum (FBS), Dulbecco’s phosphate buffered saline (PBS) without Mg²⁺ and Ca²⁺ and Hank’s balanced salts solution (HBSS) from culture grade were purchased from Euroclone SpA (Milan, Italy). Methanol was purchased from Carlo Erba SpA (Milan, Italy). Water and acetonitrile were obtained from J. T. Baker (Phillipsburg, NJ, USA). A Common Steviol Glycosides Standards Kit (steviolbioside, dulcoside A, stevioside, rebaudioside A, B, and C) was purchased from Chromadex (LGC Standards S.r.L., Milan, Italy). All other chemicals were from analytical high-performance liquid chromatography (HPLC) grade and purchased from common sources. All solvents and water were accurately degassed before being used in the analyses.