Meroapplanins A–E: Five Meroterpenoids with a 2,3,4,5-Tetrahydropyridine Motif from Ganoderma applanatum

Meroapplanins A–E (1–5)
with a 2,3,4,5-tetrahydropyridine fragment were isolated from the
fruiting bodies of Ganoderma applanatum. Their structures were elucidated by comprehensive spectroscopic
analyses. Their absolute configurations were established based on
the X-ray diffraction, electronic circular dichroism (ECD), and calculated
nuclear magnetic resonance (NMR) with DP4+ analysis. A plausible biosynthetic
pathway for 1–5 was proposed. Furthermore,
compounds 1–5, together with optically
pure compounds 1a–4a and 1b–4b, were evaluated for their protective effects
in PC12 cells damaged by H2O2. The results showed
that 3b had protective activity with a cell viability
of 82.58 ± 1.31%, compared with the model group (cell viability:
65.27 ± 1.48%).