RESUMO
(±)-Bicoryanhunine B (1), a new dimeric benzylisoquinoline alkaloid was isolated from the dried tubers of Corydalis yanhusuo by various chromatographic methods, including silica gel, Sephadex LH-20, reverse phase C18, and semi-preparative HPLC. Its structure was determined by spectroscopic methods, including UV, IR, ESI-MS, HR-ESI-MS and 1D/2D NMR. (±)-Bicoryanhunine B (1) was a moderate PD-1/PD-L1 interaction inhibitor with an IC50 value of 7.80 ± 0.49 μmol·L-1. In addition, 1 exhibited potent inhibitory activities against LPS-induced NO production in RAW 264.7 macrophages with an IC50 value of 4.83 ± 2.21 μmol·L-1.
RESUMO
Dihydrochelerythrine was isolated from the ethanol extract of Corydalis yanhusuo by chromatographic and recrystallization techniques. To our knowledge, this is the first report that dihydrochelerythrine was found to be unstable. The NMR, HPLC, and LC-MS were applied to monitor the structural conversion process of dihydrochelerythrine. The results showed that when dissolved in polar deuteration solvent (e.g., DMSO-₆ & MeOD), dihydrochelerythrine is directly converted to chelerythrine gradually. However, if used non-polar reagent (e.g.,CD₂Cl₂), the sample of dihydrochelerythrine undergoes the formation of pseudobase, chelerythrine, and bimolecular ether then followed by oxidation to oxychelerythrine as the major final product. Which leads to this phenomenon maybe is that the C-6 in dihydrochelerythrine is highly reactive to nucleophiles, and is easily converted to different derivatives in different solvents attributed to the solvent effect. This finding will contribute to the extraction and isolation, bioactivity screening, and quality evaluation of medicinal materials containing dihydrochelerythrine and other similar derivatives.