Determination of Flavonolignan Compositional Ratios in Silybum marianum (Milk Thistle) Extracts Using High-Performance Liquid Chromatography.

Milk thistle is one of the most popular ingredients in the liver protection products market. Silymarin is the main component of milk thistle and contains multiple isomers. There have been few studies focusing on the compositional ratios of silymarin isomers. In this study, we developed an HPLC method for the separation and quantification of silymarin isomers, thereby elucidating their compositional ratios. Through the analysis of more than 40 milk thistle extract products on the market, we found that the ratios, specifically Ratio 1 (the silybin B content to the silybin A content, SBNB/SBNA) and Ratio 2 (the sum of the contents of silybin B and isosilybin B to the sum of the contents of silybin A and isosilybin A, (SBNB + IBNB)/(SBNA + IBNA)), are highly consistent across milk thistle extracts, averaging approximately 1.58 and 1.28, respectively. Furthermore, such ratios were verified in milk thistle seed samples. This study introduces significant findings concerning the stable ratios among silymarin isomers in milk thistle extracts and seeds, thereby offering an innovative approach for quality assurance of milk thistle extracts.

Chemical Standardization of Milk Thistle (Silybum marianum L.) Extract Using UHPLC-MS/MS and the Method of Standard Addition.

Extracts prepared from the seeds of the medicinal plant milk thistle [Silybum marianum (L.) Gaertn. (Asteraceae)] are widely used as dietary supplements due to anti-inflammatory, antitumor, and hepatoprotective effects. Called silymarin, the main components of lipophilic extracts of milk thistle seeds are flavonoids and flavonolignans including silybin A, silybin B, isosilybin A, isosilybin B, silydianin, silychristin, taxifolin, and 2,3-dehydrosilybins. The aim of this study was to develop a method based on UHPLC-MS/MS for the chemical authentication and standardization of milk thistle silymarin. Validation included the method of standard addition to account for the lack of a blank matrix. Potential matrix effects were investigated by analyzing silymarin standards dissolved only in the initial UHPLC mobile phase. Measurements of six flavonolignans and taxifolin in the milk thistle extract using UHPLC-MS/MS with standard addition or external standard calibration produced similar results for all analytes except silydianin and 2,3-dehydrosilybin B, which showed significant peak enhancement during negative ion electrospray due to botanical matrix effects. The UHPLC-MS/MS-based method of standard addition requires <10 min per injection and is suitable for the standardization of silymarin from milk thistle in support of preclinical and clinical studies of safety and efficacy.

Effect of Field Trial on Silymarin Complex Composition and Antioxidant Assessment of Milk Thistle (Silybum marianum L. Gaertner).

Plant foods are receiving increasing attention as a valuable source of health beneficial compounds. Understanding the impact of growing conditions on the quality of milk thistle is critical for determining appropriate agro-ecological and agro-economic parameters for its production and, subsequently, food products rich in health-beneficial compounds. For this purpose, a randomized milk thistle cultivation trial was established in the experimental field of Agritec Plant Research Plc. in Sumperk, Czech Republic, and carried out for two subsequent growing seasons in 2020 and 2021. The milk thistle achenes, variety Mirel, were sown in the row width of 12.5, 25 and 37 cm; and the qualitative parameters of each field trial such as achenes yields, silymarin complex determination and also antioxidant assessment (total phenolic content, total flavonoids content, DPPH and ABTS radical scavenging activity) were evaluated. The environmental impact of the extraction process was reduced by using pressurized liquid extraction with 60% EtOH (v/v). The weather conditions during the trial as well as the row spacing of milk thistle sowing were revealed to have a significant influence on the evaluated parameters (p ≤ 0.05). The highest yields of evaluated parameters were obtained for the growing season 2021 and the row spacing of 37 cm.

Bioavailability augmentation of silymarin using natural bioenhancers: An in vivo pharmacokinetic study

Abstract Pharmacokinetic studies were carried out in male and female rats to quantify silymarin as silybin (A+B) after the oral administration of various silymarin formulations combined with three bioenhancers, namely, lysergol, piperine, and fulvic acid, and compared with plain silymarin formulation (control). A non-compartmental analysis, model independent analysis, was utilized, and various pharmacokinetic parameters (C max, T max, and AUC 0-t) were calculated individually for each treatment group, and the values were expressed as mean ± SEM (n = 6). Plasma samples obtained from the rats were analyzed for the concentration of silymarin through a validated RP-HPLC method and on the basis of data generated from the pharmacokinetic studies. Results indicated that the bioenhancers augmented pharmacokinetic parameters and bioavailability increased 2.4-14.5-fold in all the formulations compared with the control. The current work envisages the development of an industrially viable product that can be further subjected to clinical trials and scientifically supports the development of silymarin as a contemporary therapeutic agent with enhanced bioavailability and medicinal values.

Extraction, Chemical Composition, Antioxidant Property, and In-vitro Anticancer Activity of Silymarin from Silybum marianum on Kb and A549 Cell Lines.

INTRODUCTION: This study aimed to evaluate the antioxidant property of Silymarin (SM) extracted from the seed of Silybum marianum and its anticancer activity on KB and A549 cell lines following 24, 48, and 72 h of treatment. METHODS: Ten grams of powdered S. marianum seeds were defatted using n-hexane for 6 hours and then extracted by methanol. The Silymarin extracted of extraction components. The extracted components of Silymarin were measured by spectrophotometric assay and HPLC analysis. 2, 2- diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, phenol content, total flavonoid content, and total antioxidant capacity were measured to detect the antioxidant properties of SM. The anticancer activity of the SM on cell lines evaluated by MTT. RESULTS: In HPLC analysis, more than 50% of the peaks were related to silybin A and B. SM was reduced DPPH (the stable free radical) with a 50% inhibitory concentration (IC50) of 6.56 µg/ ml in comparison with butylated hydroxyl toluene (BHT), which indicated an IC50 of ~3.9 µg/ ml. The cytotoxicity effect of SM on the cell lines was studied by MTT assay. The cytotoxicity effect of the extracted Silymarin on KB and A549 cell lines was observed up to 80 and 70% at 156 and 78 µg/ml, respectively. The IC50 value of the extracted SM on KB and A549 cell lines after 24 hours of treatment was seen at 555 and 511 µg/ml, respectively. CONCLUSION: Due to the good antioxidant and anticancer properties of the isolated Silymarin, its use as an anticancer drug is suggested.

In Silybum marianum Italian wild populations the variability of silymarin profiles results from the combination of only two stable chemotypes.

Silybum marianum (L.) Gaertn. is an important medicinal plant belonging to Mediterranean flora. The medicinal properties of the species are mainly due to silymarin, a combination of different flavonolignans contained in the fruit. As for silymarin, so far a wide variability of possible S. marianum chemotypes has been described. In the present study the flavonolignan profile of 40 different S. marianum wild accessions was analysed at both population and single plant level, further extending the analysis to progenies derived from crosses between parental lines with different chemotypes. The results of this work indicate that S. marianum wild populations can be composed either of individuals with the same chemotype, or heterogeneous mixtures of individuals characterized by different chemotypes. Only three chemotypes (A, B and C) have been identified among Italian wild populations. Based on data collected we furthermore propose that chemotype C is the result of the hybridization between A and B chemotypes. If assessed at single plant level, chemotypes are extremely stable therefore evidencing a strong genetic control of silymarin biosynthetic pathway. Chemotypes A and B are present in all the analysed regions and no clear correlation between chemotypes and geographic features has been found. In conclusion, this work provides a general procedure for the characterization of different and stable chemotypes, for a deeper understanding of silymarin biosynthetic pathway, and in order to implement S. marianum breeding programmes aiming to improve silymarin quality.

HPTLC Separation of a Hepatoprotective Combination in Pharmaceutical Formulation and Human Plasma.

A binary mixture of Silymarin (SR) and Vitamin E (VE) acetate, of an antioxidant and a hepatoprotective effect, has been analyzed using a sensitive, selective and economic high performance thin layer chromatographic (HPTLC) method in their pure forms, pharmaceutical formulation and spiked human plasma. SR and VE were separated on 60F254 silica gel plates using hexane:acetone:formic acid (7:3:0.15, v/v/v) as a developing system with UV detection at 215 nm. The method was evaluated for linearity, accuracy, precision, selectivity, limit of detection (LOD) and limit of quantification (LOQ). SR and VE were detected in the linear range of 0.2-2.5 and 0.2-4.5 µg/band, respectively. Method validation was done as per ICH guidelines and acceptable results of accuracy of 99.86 ± 1.190 and 100.22 ± 1.609 for SR and VE, respectively were obtained. The method has been successfully applied for determination of the studied drugs in their pharmaceutical formulation without any interference from excipients, and in spiked plasma samples. Results obtained by the developed HPTLC-densitometric method were statistically compared to those obtained by the reported HPLC methods and no significant difference was found between them.

Liquid chromatography-drift tube ion mobility-mass spectrometry as a new challenging tool for the separation and characterization of silymarin flavonolignans.

Silymarin, milk thistle (Silybum marianum) extract, contains a mixture of mostly isomeric bioactive flavonoids and flavonolignans that are extensively studied, especially for their possible liver-protective and anticancer effects. Because of the differing bioactivities of individual isomeric compounds, characterization of their proportion in a mixture is highly important for predicting its effect on health. However, because of silymarin's complexity, this is hardly feasible by common analytical techniques. In this work, ultraperformance liquid chromatography coupled with drift tube ion mobility spectrometry and quadrupole time-of-flight mass spectrometry was used. Eleven target silymarin compounds (taxifolin, isosilychristin, silychristins A and B, silydianin, silybins A and B, 2,3-cis-silybin B, isosilybins A and B and 2,3-dehydrosilybin) and five unknown flavonolignan isomers detected in the milk thistle extract were fully separated in a 14.5-min analysis run. All the compounds were characterized on the basis of their accurate mass, retention time, drift time, collision cross section and fragmentation spectra. The quantitative approach based on evaluation of the ion mobility data demonstrated lower detection limits, an extended linear range and total separation of interferences from the compounds of interest compared with the traditional approach based on evaluation of liquid chromatography-quadrupole time-of-flight mass spectrometry data. The following analysis of a batch of milk thistle-based food supplements revealed significant variability in the silymarin pattern, especially in the content of silychristin A and silybins A and B. This newly developed method might have high application potential, especially for the characterization of materials intended for bioactivity studies in which information on the exact silymarin composition plays a crucial role. Graphical Abstract.

Linear regression analysis of silychristin A, silybin A and silybin B contents in Silybum marianum.

Quantitative correlations between the contents of the flavonolignans silychristin A and silybins A/B provide biosynthetic clues that support a pathway in which one mesomeric form of a taxifolin radical is undergoing an oxidative coupling with a coniferyl alcohol radical. The flavonolignan content and patterns reported in the literature for 53 samples, representing populations of the Silybum marianum plant growing in different parts of the world, were subject to a meta-analysis. Linear regression analyses were carried out on these data sets, and a mathematical model was derived that predicts the content of silychristin A relative to the metabolomic pattern of its congeners. The validity of the model was verified by applying it to test samples. This approach could potentially become a tool to enhance the understanding of both the relative composition of the silymarin complex and the biosynthetic pathways that underlie its formation.

Evaluating the protective potency of Acacia hydaspica R. Parker on histological and biochemical changes induced by Cisplatin in the cardiac tissue of rats.

BACKGROUND: Increase oxidative trauma is the main cause behind Cisplatin (CP) induced cardiotoxicity which restricts its clinical application as anti-neoplastic prescription. Acacia hydaspica is a natural shrub with diverse bioactivities. Acacia hydaspica ethyl acetate extract (AHE) ameliorated drug-induced cardiotoxicity in animals with anti-oxidative mechanisms. Current study aimed to evaluate the protective potential of A. hydaspica against cisplatin-induced myocardial injury. METHODS: Rats were indiscriminately distributed into six groups (n = 6). Group 1: control; Groups 2: Injected with CP (7.5 mg/kg bw, i.p, single dose) on day 16; Group 3: Treated for 21 days with AHE (400 mg/kg b.w, oral); Group 4: Received CP injection on day 16 and treated with AHE for 5 days post injection; Group 5: Received AHE (400 mg/kg b.w/day, p.o.) for 21 days and CP (7.5 mg/kg b.w., i.p.) on day 16; Group 6: Treated with silymarin (100 mg/kg b.w., p.o.) after 1 day interval for 21 days and CP injection (7.5 mg/kg b.w., i.p.) on day 16. On 22nd day, the animals were sacrificed and their heart tissues were removed. Cisplatin induced cardiac toxicity and the influence of AHE were evaluated by examination of serum cardiac function markers, cardiac tissue antioxidant enzymes, oxidative stress markers and histology. RESULTS: CP inoculation considerably altered cardiac function biomarkers in serum and diminished the antioxidant enzymes levels, while increased oxidative stress biomarkers in cardiac tissues AHE treatment attenuated CP-induced deteriorations in creatine kinase (CK), Creatine kinase isoenzymes MB (CK-MB), cardiac Troponin I (cTNI) and lactate dehydrogenase (LDH) levels and ameliorated cardiac oxidative stress markers as evidenced by decreasing lipid peroxidation, H2O2 and NO content along with augmentation in phase I and phase II antioxidant enzymes. Additionally, CP inoculation also induced morphological alterations which were ameliorated by AHE. In pretreatment group more significant protection was observed compared to post-treatment group indicating preventive potential of AHE. The protective potency of AHE was comparable to silymarin. CONCLUSION: Results demonstrate that AHE attenuated CP induce cardiotoxicity. The polyphenolic metabolites and antioxidant properties of AHE might be responsible for its protective influence.

The decrease of lasalocid residue in the edible tissues by silymarin supplementation of chicken diet.

Widespread use of coccidiostats, in spite of beneficial control of protozoan infections in poultry, implies a risk of residues in edible tissues, and there is increasing interest in the development of strategies for prevention of veterinary drugs residue in food-producing animals. The aim of this study is assigned to clarify the impact of silymarin addendum in the diet on lasalocid concentration in the liver and breast muscles from the broiler. Four groups of chickens received a feed with lasalocid at levels between 75 and 200 mg kg-1. Other four groups received a feed with lasalocid (75-200 mg kg-1) plus silymarin. Significant differences of lasalocid concentrations between the liver and breast muscles were observed. Moreover, the chickens from the groups supplemented with silymarin shown significant decreases of lasalocid concentrations in the analysed tissues. The herbal substance did not counteract the ionophore in the treatment of coccidiosis and did not change biochemical parameters of blood. These findings suggest that silymarin might be used in chicken feeding in order to reduce the risk from lasalocid contamination of the broiler edible tissues.

Tyrosinase inhibitory study of flavonolignans from the seeds of Silybum marianum (Milk thistle).

Anti-melanogenesis effects of silymarin from milk thistle have been reported recently, but detailed tyrosinase inhibition properties of individual components have not been investigated. This study purported to substantiate tyrosinase inhibition and its mechanism based on a single metabolite. The responsible components for tyrosinase inhibition of target source were found out as flavonolignans which consist of isosilybin A (1), isosilybin B (2), silydianin (3), 2,3-dihydrosilychristin (4), silychristin A (5), silychristin B (6) and silybin (7), respectively. The isolated flavonolignans (1-7) inhibited both monophenolase (IC50 = 1.7-7.6 µM) and diphenolase (IC50 = 12.1-44.9 µM) of tyrosinase significantly. Their inhibitions were 10-fold effective in comparison with their mother skeletons (8-10). Inhibitory functions were also proved by HPLC analysis using N-acetyl-l-tyrosine as substrate. The predominant formation of Emet·I was confirmed from a long prolongation of lag time and a decrease of the static state activity of the enzyme. All tested compounds had a significant binding affinity to tyrosinase with KSV values of 0.06-0.27 × 104 L·mol-1, which are well correlated with IC50s. In kinetic study, all flavonolignan (1-7) were mixed type I (KI < KIS) inhibitors, whereas their mother skeletons (8-10) were competitive ones. The UPLC-ESI-TOF/MS analysis showed that the isolated inhibitors are the most abundant metabolites in the target plant.

PRiME pass-through purification of lignans in Silybum marianum and UPLC-MS/MS analysis.

A PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure was developed for the extraction and purification of silychristins A and B, silybins A and B, isosilybins A and B, and silydianin in Silybum marianum. After optimizing the extracting solvent types and the sample loading volume, the crude extract was diluted to 3 mL with 95% acetonitrile and then loaded on the PRiME cartridge. The eluate was analyzed by ultra-performance liquid chromatography and tandem mass spectrometry (UPLC-MS/MS). All the target analytes were deprotonated as [M-H]- at m/z 481 by conducting collision-induced dissociation (CID), and the major fragment ions were m/z 463 ([M-H2O-H]-), 453 ([M-CO-H]-), 355 ([M-C6H6O3-H]-), 301 ([M355-CO2-H]-), and 179 ([C10H11O3]-). Afterwards, this method was validated in terms of linearity (R2 > 0.9990), intra-day precision (1.02%-3.79%), inter-day precision (1.59%-4.87%), sensitivity (LOD ≤ 0.45 µg·kg-1 and LOQ ≤ 1.50 µg·kg-1), and recovery (76.9-103.4%, RSD < 8.90%). Finally, the proposed protocol was successfully applied to eight batches of S. marianum samples. The total content of the seven active compounds varied amongst the batches from different places of origin.

3-Amino-5-pyridin-3-yl-1,2,4-triazole, a novel fluorescence probe for trace analysis of silymarin in bulk material, pharmaceutical dosage forms and human plasma: Further insights on reaction mechanism using computational molecular modeling and NMR spectroscopy.

A rapid, highly sensitive and roubst spectrofluorimetric method was developed for trace analysis of silymarin (SLM) in active pharmaceutical ingredient (API), pharmaceutical preparations and human plasma. The proposed method is based on reaction of SLM with a novel reagent; 3-amino-5-pyridin-3-yl-1,2,4-triazole (3-APT); in the presence of 0.04 M sodium hydroxide. The formed fluorescent product was formed within 5 min and was measured at 504 nm after excitation at 390 nm. All reaction parameters were optimized and the proposed method was validated according to ICH guidelines. The developed method was linearly correlated at the concentration range of 0.05-8 µg mL-1 with good correlation coefficient 0.9993, limit of detection 10.79 ng mL-1 and limit of quantitation 32.71 ng mL-1. The relative standard deviations %RSD values were 1.59-2.69% and 1.47-2.62% in case of intra- and inter-day precision, respectively. Computational molecular modeling and NMR spectroscopy were used to identify the reaction mechanism between SLM and 3-APT. The proposed method was employed for determination of SLM in API or bulk material, pharmaceutical capsules and sachets. Further, the method was sensitive enough to be applied for analysis of the free (unconjugated) SLM flavonolignans in human plasma samples.

Differential accumulation of silymarin induced by exposure of Silybum marianum L. callus cultures to several spectres of monochromatic lights.

Silybum marianum L. (Milk thistle) is one of the most extensively studied medicinal herbs with well-known hepatoprotective activity. Light is considered as a key abiotic elicitor influencing several physiological processes in plants, including the biosynthesis of secondary metabolites. In this study, we investigated the influence of light quality on morphological and biochemical aspects in in vitro grown leaf-derived callus cultures of S. marianum. Combination of 6-benzylaminopurine (BAP 2.5 mg/L) and α-naphthalene acetic acid (NAA 1.0 mg/L) resulted in optimum callogenic response (97%) when placed under cool-white light with 16 h light and 8 h dark. Red light significantly increased the total phenolic content (TPC), total flavonoid content (TFC), antioxidant and superoxide dismutase (SOD) activities while highest peroxidase (POD) activity was recorded for the dark grown cultures, followed by green light grown cultures. HPLC analysis revealed enhanced total silymarin content under red light (18.67 mg/g DW), which was almost double than control (9.17 mg/g DW). Individually, the level of silychristin, isosilychristin, silydianin, silybin A and silybin B were found greatest under red light, whereas green spectrum resulted in highest accumulation of isosilybin A and isosilybin B. Conversely, the amount of taxifolin was found maximum under continuous white light (0.480 mg/g DW) which was almost 8-fold greater than control (0.063 mg/g DW). A positive correlation was found between the TPC, TFC and antioxidant activities. This study will assist in comprehending the influence of light quality on production of valuable secondary metabolites in in vitro cultures of S. marianum L.

Are LOD and LOQ Reliable Parameters for Sensitivity Evaluation of Spectroscopic Methods?

The limit of detection (LOD) and the limit of quantification (LOQ) are common parameters to assess the sensitivity of analytical methods. In this study, the LOD and LOQ of previously reported terbium sensitized analysis methods were calculated by different methods, and the results were compared with sensitivity parameters [lower limit of quantification (LLOQ)] of U.S. Food and Drug Administration guidelines. The details of the calibration curve and standard deviation of blank samples of three different terbium-sensitized luminescence methods for the quantification of mycophenolic acid, enrofloxacin, and silibinin were used for the calculation of LOD and LOQ. A comparison of LOD and LOQ values calculated by various methods and LLOQ shows a considerable difference. The significant difference of the calculated LOD and LOQ with various methods and LLOQ should be considered in the sensitivity evaluation of spectroscopic methods.

Rapid qualitative analysis of 2 flavonoids, rutin and silybin, in medical pills by direct analysis in real-time mass spectrometry (DART-MS) combined with in situ derivatization.

Direct analysis in real-time mass spectrometry (DART-MS) with in situ silylation was used for the rapid analysis of the flavonoids silybin ((2R,3R)-3,5,7-trihydroxy-2-[3-(4-hydroxy-3-methoxyphenyl)-2-hydroxymethyl-2,3-dihydrobenzo[1,4]dioxin-6-yl]chroman-4-one) and rutin (quercetin-3-O-rutinoside). Three different derivatization reagents, hexamethyldisilazane/trimethylchlorosilane/pyridine (HMDS/TMCS/pyridine), N,O-bis(trimethylsilyl)acetamide/trimethylchlorosilane/N-trimethylsilyimidazole (BSA/TMCS/TMSI), and N,O-bis(trimethylsilyl)trifluoroacetamide/trimethylchlorosilane (BSTFA/TMCS), were applied. Silybin and rutin were detected with various degrees of silylation, and the formation of dimers with pyridine and imidazole was also observed. HMDS/TMCS/pyridine was the best choice for the DART-MS analysis of silybin, and BSA/TMCS/TMSI was the most effective for the detection of rutin. The effects of the DART source temperature on desorption, ionization, in-source fragmentation, dimer formation, and hydrolysis of the trimethylsilyl groups were also studied. In addition, the collision-induced dissociation properties of the derivatized silybin and rutin were explored. With our in situ silylation method, the derivatized bioactive compounds in intact medical pills could also be detected by DART-MS.

The silymarin composition and why does it matter???

The extract from milk thistle (Silybum marianum (L.) Gaertn. (Asteraceae)), known as silymarin, contains a variety of flavonolignans and displays antioxidant, anti-inflammatory, immunomodulatory and hepatoprotective properties. As silybin is the main component of silymarin, the literature mainly focuses on this compound, ignoring all other components. This leads to problems in reproducibility of scientific results, as the exact composition of silymarin is often unknown and can vary to a certain degree depending on the processing, chemo-variety of the plant used and climatic conditions during the plant growth. There are studies dealing with the analytical separation and quantification of silymarin components as well as studies focused on silymarin content in clinically used drugs, in various plant parts, seasons, geographic locations etc. However, no comparison of detail flavonolignan profiles in various silymarin preparations is available to date. Also, as a result of the focus on the flavonolignans; the oil fraction, which contains linoleic, oleic and palmitic acids, sterols, tocopherol (vitamin E) and phospholipids, has been neglected. Due to all these factors, the whole plant is used e.g. as animal feed, the leaves can be eaten in salads and seed oil, besides culinary uses, can be also utilized for biodiesel or polymer production. Various HPLC separation techniques for the determination of the content of the flavonolignans have been vastly summarized in the present review.

Development of a Terbium-Sensitized Fluorescence Method for Analysis of Silibinin.

Silibinin is a natural flavonoid with potent anticancer properties, as shown in both in vitro and in vivo experiments. Various methods have been used for silibinin analysis. Terbium-sensitized fluorescence methods have been widely used for the determination of drugs in pharmaceutical preparations and biological samples in recent years. The present work is aimed at providing a simple analytical method for the quantitative determination of silibinin in aqueous solutions based on the formation of a fluorescent complex with terbium ion. Terbium concentration, pH, and volume of buffer, the important effective parameters for the determination of silibinin by the proposed method, were optimized using response surface methodology. The fluorescence intensity of silibinin was measured at 545 nm using λex = 334 nm. The developed method was applied for the determination of silibinin in plasma samples after protein precipitation with acetone. Under optimum conditions, the method provided a linear range between 0.10 and 0.50 mg/L, with a coefficient of determination (R2) of 0.997. The LOD and LOQ were 0.034 and 0.112 mg/L, respectively. These results indicate that the developed method is a simple, low-cost, and suitable analytical method for the quantification of silibinin in aqueous solution and plasma samples.

Protective Effect of Silybum marianum and Silibinin on Endothelial Cells Submitted to High Glucose Concentration.

Silybum marianum Gaertn. (Milk thistle) has been used since ancient times for the relief of liver diseases characterized by intense oxidative stress such as inflammatory liver disease and cirrhosis. As oxidative stress by hyperglycemia is involved in micro- and macrovascular complications of type 2 diabetes, our aim was to assess the protective effect of milk thistle seed extract against oxidative stress induced by a high glucose concentration on endothelial cells (EA.hy926 cells). High-performance liquid chromatographic analysis shows flavonolignans silychristin and silibinin A and B as major components. No cell toxicity was observed for concentrations up to 100 µg/mL of milk thistle extract for 24 h. Concentrations of 5-25 µg/mL of the extract were used to assess the protective effect on EA.hy926 cells treated with 30 mM glucose for 24 h. Oxidative damage by 30 mM glucose was shown as a significant decrease in reduced glutathione and a significant increase in protein carbonyls and antioxidant enzyme activities. S. marianum extract recovered reduced glutathione and balanced the elevated carbonyls and enzyme activity. Silibinin alone also recovered reduced glutathione and antioxidant enzymes. S. marianum protects endothelial cell against oxidative damage by modulating antioxidant enzyme activity, reduced glutathione, and protein carbonyl levels.