Optimization and single-laboratory validation of a method for the determination of flavonolignans in milk thistle seeds by high-performance liquid chromatography with ultraviolet detection

Abstract

Seeds of milk thistle, Silybum marianum (L.) Gaertn., are used for treatment and prevention of liver disorders and were identified as a high priority ingredient requiring a validated analytical method. An AOAC International expert panel reviewed existing methods and made recommendations concerning method optimization prior to validation. A series of extraction and separation studies were undertaken on the selected method for determining flavonolignans from milk thistle seeds and finished products to address the review panel recommendations. Once optimized, a single-laboratory validation study was conducted. The method was assessed for repeatability, accuracy, selectivity, LOD, LOQ, analyte stability, and linearity. Flavonolignan content ranged from 1.40 to 52.86 % in raw materials and dry finished products and ranged from 36.16 to 1570.7 μg/mL in liquid tinctures. Repeatability for the individual flavonolignans in raw materials and finished products ranged from 1.03 to 9.88 % RSDr, with HorRat values between 0.21 and 1.55. Calibration curves for all flavonolignan concentrations had correlation coefficients of >99.8 %. The LODs for the flavonolignans ranged from 0.20 to 0.48 μg/mL at 288 nm. Based on the results of this single-laboratory validation, this method is suitable for the quantitation of the six major flavonolignans in milk thistle raw materials and finished products, as well as multicomponent products containing dandelion, schizandra berry, and artichoke extracts. It is recommended that this method be adopted as First Action Official Method status by AOAC International.

Single Laboratory Validation of a Quantitative Core Shell-Based LC Separation for the Evaluation of Silymarin Variability and Associated Antioxidant Activity of Pakistani Ecotypes of Milk Thistle (Silybum Marianum L.)

“…The superior efficiency and the improved peak symmetry and resolution of core-shell columns, when compared to the most common monolithic columns, for the analysis of the silybin (A and B) diastereoisomers were already described [ 22 , 23 , 41 ]. Moreover, the core-shell technology is enough versatile to allow for an easier possible transition of the present protocol to other methodologies, such as UPLC [ 41 , 42 , 43 , 44 ]. The typical LC-MS chromatogram (with detection set at 280 nm) is presented in Figure 2 and Figure S1 .…”

The chemical composition, antioxidant activity, and antiproliferative activity of selected seed flours

“…The chemical compositions of two sources of milk thistle seeds were extracted with 100% methanol and analyzed by Mudge and others. Silychristin, silydianin, silybin A, silybin B, isosilybin A, and isosilybin B were detected (Mudge et al, 2015). Choe et al identified several major chemicals in milk thistle seed flour as well.…”

Evaluation of the status quo of polyphenols analysis: Part II—Analysis methods and food processing effects

“…The detection is carried out with UV detector at 280 nm (Nadeem, Taj Khan, Khan, & Ajmal Shah, 2020). For quantification of lignans, many simple (i.e., 13 C NMR spectroscopy; Nam, Paoli, Castola, Casanova, & Bighelli, 2011) or advanced techniques coupled with HPLC have been applied (Mudge, Paley, Schieber, & Brown, 2015;Table 4). For instance; Chen et al (2019) developed a simple and rapid method based on matrix solid-phase dispersion (MSPD) combined with silica gel and eluted with methanol and HPLC, where HPLC-MS/MS triple quadrupole was also utilized for the quantification of lignans found in espresso coffee.…”

“…For quantification of lignans, many simple (i.e., 13 C NMR spectroscopy; Nam, Paoli, Castola, Casanova, & Bighelli, 2011) or advanced techniques coupled with HPLC have been applied (Mudge, Paley, Schieber, & Brown, 2015; Table 4). For instance; Chen et al.…”