Isolation of two rare N-glycosides from Ginkgo biloba and their anti-inflammatory activities

Two rare N-β-D-glucopyranosyl-1H-indole-3-acetic acid conjugates, N-[2-(1-β-D-glucopyranosyl)-1H-indol-3-yl)acetyl]-L-glutamic acid (1) and N-[2-(1-β-D-glucopyranosyl)-1H-indol-3-yl)acetyl]-L-aspartic acid (2) were isolated from Ginkgo biloba. The structures were elucidated by analyses of HRMS and NMR spectroscopic data. In addition, a simplified and efficient synthetic route for compounds 1 and 2 is also disclosed to determine the absolute configurations of them. This concise syntheses of compounds 1 and 2 may facilitate studies of the biology of this type alkaloids. Compounds 1 and 2 were also tested for their cytotoxic and anti-inflammatory activities. The biological evaluation showed that compounds 1 and 2 led to the decrease of interleukin (IL)-6, nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 at mRNA level in lipopolysaccharide (LPS)-stimulated murine macrophage RAW264.7 cells.