Pseudoheterines A–I, Polyheterocyclic Alkaloids from Pseudostellaria heterophylla with Neuroprotective Activities

Nine
undescribed polyheterocyclic pyrrole alkaloids,
pseudoheterines
A–I (1–7, 11,
and 12), along with four known analogues (8–10 and 13), were isolated from
the plant Pseudostellaria heterophylla. The structures and absolute configurations of compounds 1–7, 11, and 12 were
determined by extensive spectroscopic analysis, ECD calculations,
and X-ray diffraction. Compounds 1–6 are six unprecedented tetracyclic alkaloids with a triheterocyclic
moiety, pyrrole-dihydrofuran-pyrrolidone core. Compounds 1, 3, and 5 present a fourth aromatic heterocyclic
ring D, while 2, 4, and 6 possess
an aromatic ring attached by an ester linkage. Compounds 6 and 9 exhibited neuroprotective activities by inhibiting
apoptosis in CdCl2-induced PC-12 cells, and ameliorated
CdCl2-induced neural damage in zebrafish.