Distinctive effect on nerve growth factor-induced PC12 cell neurite outgrowth by two unique neolignan enantiomers from Illicium merrillianum

Merrillianoid ( 1 ), a racemic neolignan possessing the characteristic benzo-2,7-dioxabicyclo[3.2.1]octane moiety, was isolated from the branches and leaves of Illicium merrillianum . Chiral separation of 1 gave two enantiomers (+)− 1 and (−)− 1 . The structure of 1 was established by comprehensive spectroscopic analysis and single crystal X-ray diffraction. The absolute configurations of enantiomers were determined by quantum mechanical calculation. Compound (+)− 1 exhibited a better neurotrophic activity than racemate 1 by promoting nerve growth factor (NGF) induced PC12 cell neurite outgrowth, while (−)− 1 showed a distinctive inhibitory effect. Furthermore, a mechanism study indicated that the two enantiomers influenced NGF-induced neurite outgrowth of PC12 cells possibly by interacting with the trkA receptor and extracellular signal regulated kinases 1/2 (ERK1/2) and mitogen-activated protein kinase (MEK) in Ras/ERK signal cascade. But the phosphorylation level of serine/threonine kinase Akt1 and Akt2 in PI3K/Akt signal pathway showed no significant difference between (+)− 1 and (−)− 1 .