8?10 While some flavonoids were already reported to activate PPAR��,42,43 this is the first report demonstrating PPAR�� activation by a flavonolignan-type compound. In summary, it is reported for the first time that the flavonolignan isosilybin A (3) from the milk thistle seed extract silymarin acts as a partial PPAR�� find protocol agonist. Being a new-scaffold PPAR�� activator, 3 might serve as a lead for future development of new PPAR�� agonists. The question as to whether PPAR�� activation by 3 might be clinically relevant for the use of silymarin as an herbal remedy cannot be conclusively answered yet and deserves further investigation. Experimental Section Chemicals, Cell Culture Reagents, and Plasmids Dulbecco��s modified Eagle��s medium (DMEM), containing 4.

5 g/L glucose, and l-glutamine were purchased from Lonza (Basel, Switzerland). Fetal bovine serum (FBS) was from Gibco (Lofer, Austria). Silymarin was purchased from Sigma (SO-292-10g). Taxifolin (7) was purchased from Roth, Karlsruhe, Germany (5797.2). Compounds 1, 2, 3, and 4 were isolated and structurally identified as described previously.44 Silydianin (6) was isolated and structurally identified as described.45 The isolation of silychristin (5) is described below. The PPAR�� antagonist T0070907 was purchased from Cayman (Ann Arbor, MI, USA), and pioglitazone was from Molekula Ltd. (Shaftesbury, UK). Solvents used for HPLC analyses were of gradient grade. The investigated compounds or dried extracts were dissolved in dimethyl sulfoxide (DMSO), aliquoted, and stored at ?20 ��C for further use.

The final concentration of the solvent vehicle DMSO was 0.1% or lower in all performed experiments. The expression plasmid with human PPAR�� (pSG5-PL-hPPAR-gamma1)46 was provided by Prof. Beatrice Desvergne and Prof. Walter Wahli (Center for Integrative Genomics, University of Lausanne, Switzerland), and the luciferase reporter plasmid (tk-PPREx3-luc)47 was kindly supplied by Prof. Ronald M. Evans (Salk Institute for Biological Studies, San Diego, CA, USA). All other chemicals were obtained from Sigma�CAldrich (Vienna, Austria). Isolation of Silychristin (5) Isolation was accomplished by preparative HPLC separation of silymarin on a Varian Prep Star SD-1 solvent delivery system equipped with a Dynamax UV-1 absorbance detector, which was set to 280 nm. A 100 mg aliquot of silymarin was dissolved in 0.

5 mL of DMSO and 2 mL of methanol and sonicated, and the solution was centrifuged. An Ultra SEP ES RP-18 column (250 �� 20 mm, 10 ��m) was used as a stationary phase, and a gradient of methanol in water (0�C40 min: methanol�Cwater 30:70�C55:45; 40�C50 min 55:45�C100:0) was used as mobile phase (flow rate: 6 mL/min). The peak of 5 (tR 38 min) was collected, and the Cilengitide solvent was evaporated. A yellowish powder (12 mg) was obtained.