Complex Evaluation of Antioxidant Capacity of Milk Thistle Dietary Supplements

Abstract

Numerous in vitro assays are used to characterize the antioxidant properties of natural-based matrices. However, many of them generate contradictory and non-compliant results. In our study, we focused on the characterization of traditionally used biochemical (2,2′-azino-bis-(3-ethylbenzothiazoline-6 sulfonic acid) (ABTS), Oxygen Radical Absorption Capacity (ORAC), and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) and cellular (CAA) antioxidant tests on a broad set of milk thistle dietary supplements containing silymarin. In addition to 26 commercially available preparations, also the natural silymarin extract available from Sigma Aldrich, St. Louis, MI, USA, and a model mixture of pure flavonoid/flavonolignans mimicking the silymarin composition were investigated as control samples. Significant differences in the antioxidant capacity of the supplements were observed. Unlike the DPPH, the results of the ABTS and ORAC methods correlated with the silymarin components determined by U-HPLC-HRMS/MS. The responses in CAA were considerably lower than in other assays. Silymarin exhibited a significantly higher antioxidant capacity than the artificially prepared flavonoid/flavonolignans mixture in all tests, indicating possible presence of other antioxidants of natural origin. The follow-up U-HPLC-HRMS/MS screening revealed the presence of tens of non-silymarin compounds with reported antioxidant activity (not only in the silymarin extract, but also in the milk thistle preparations). The sum of the total phenolics and the sum of the simple phenolics correlated with CAA results more than silymarin.

Fucus vesiculosus and Ascophyllum nodosum Ameliorate Liver Function by Reducing Diet-Induced Steatosis in Rats

“…Our data indicate that the algal extract decreases bilirubin plasma levels, as well as ALT and AST, thereby confirming its beneficial effects on liver function, which are also demonstrated by histology. On the contrary, dietary supplements based on Silybum marianum (milk thistle), a plant with a well-recognized antioxidant [25] and hepatoprotective actions (see, e.g., [26] and references therein) have been demonstrated to improve liver function by increasing bilirubin levels and suppressing UGT1A1, the enzyme responsible for bilirubin conjugation, and decreasing body weight [27]. Furthermore, bilirubin was recently found to act through the nuclear receptor PPARα [28,29] to reduce body weight.…”

Phytochemical Composition and In Vitro Biological Activity of Iris spp. (Iridaceae): A New Source of Bioactive Constituents for the Inhibition of Oral Bacterial Biofilms

“…plants was created based on a scientific literature search [ 23 ]. Then, those predicted compounds were screened in a targeted manner in the crude extracts using UHPLC-HRMS/MS analysis, as previously described by [ 24 ] with some modifications. Chromatographic separation was achieved using a 150 × 2.1 mm i.d., 1.7 μm Acquity UPLC ® BEH C 18 column (Waters, Milford, MA, USA) in a chromatographic Agilent 1290 Infinity LC System (Agilent Technologies, Santa Clara, CA, USA).…”

“…The correlation coefficients were calculated using the automatic function "CORREL" in Microsoft®Office Excel according to [24]. The following variables were used as the matrix: (I) IC 50 for specific biological activity and (II) the peak areas of compounds detected and tentatively identified by targeted UHPLC-HRMS/MS screening.…”

Comparison of Chemical Composition and Biological Activities of Eight Selaginella Species

“…The antioxidant activity was tested using the standard ORAC assay [ 65 ]. The crude extracts were analyzed using binary dilution in the concentration range of 0.1–2500 mg/L in 3 replicates.…”