Hepatoprotective activity assessment of amino acids derivatives of picroside Ⅰ and Ⅱ

Picrorhiza kurroa has a long medicinal history as a traditional medicinal plant in China and India that is widely used in clinical treatments. It is a common treatment for liver diseases, fever, diarrhoea, indigestion, and some other diseases. Modern pharmacological studies proved that P. kurroa rhizomes have high levels of picroside I and II, which were identified as main constituents with anti-inflammatory and hepatoprotective activities. In our study, we used picroside I and II as the lead compounds to generate derivatives by reactions with Boc-valin or Boc-proline, which underwent dehydration and condensation with the hydroxyl groups in the lead compounds in the presence of coupling reagent N,N'-dicyclohexylcarbodiimide. We synthesized 11 derivatives and examined their hepatoprotective effects in vitro by assessing the proliferation rates of H₂ O₂ -exposed HepG2 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. We found that some derivatives promoted higher proliferation rates in HepG2 cells than the natural compounds before derivatization, suggesting that those derivatives possessed an improved hepatoprotective capacity. The novel derivatization strategy for picrosides had the additional benefit that the esterification of their hydroxyl groups created not only derivatives with increased stability but also with improved pharmacokinetic properties and potentially prolonged half-life.

Keywords: Cell culture; Hepatoprotective activity; Picrorhiza kurroa; Picroside; Structural Modification.