New Lignans from the Flower of Forsythia koreana and Their Suppression Effect on VCAM-1 Expression in MOVAS Cells

Six lignans including two new lignans were obtained as the principal components of the Forsythia koreana flowers via silica gel (SiO₂), octadecyl SiO₂ (ODS) as well as Sephadex LH-20 column chromatography. In addition to two new lignans, named koreanaside A ((7R,8S,7′R,8′S)-7,7′-diepoxy-5′-hydroxy-3,3′-dimethoxylignan 4-O-β-d-glucopyranoside) and koreanaside B ((7R,8S,7′S,8′R)-7,9′-epoxy-9,5′,7′-trihydroxy-3,3′-dimethoxylignan 4-O-β-d-glucopyranoside), four known lignans were identified to be (+)-phylligenin, (−)-epipinoresinol, pinoresinol, and tinosposide A. The structures and absolute configurations of koreanasides A and B were established by means of analysis of spectroscopic data (NMR, IR, FAB-MS, and CD), whereas the structures of known lignans were identified by comparison their NMR and MS values with those in the reported literature. Their chemical structures including configuration were established by means of analysis of spectroscopic data (NMR, IR, FAB-MS, and CD) but also comparison of their NMR and MS values with those in the reported literature. This is the first article for isolation of six lignans of F. koreana flowers. Koreanasides A and B showed high radical scavenging activity with oxygen radical absorbance capacity (ORAC) values of 0.97 ± 0.01 and 1.02 ± 0.01, respectively. Koreanaside A also prohibited expressing VCAM-1 in MOVAS cells with 80.5% at 25 mg/mL.