Structurally Diverse Alkaloids from the Seeds of Peganum harmala

摘要

Investigation of the alkaloids from Peganum harmala seeds yielded two pairs of unique racemic pyrroloindole alkaloids, (±)-peganines A–B (>1–2); two rare thiazole derivatives, peganumals A–B (>3–4); six new β-carboline alkaloids, pegaharmines F–K (>5–10); and 12 known analogues. Their structures, including stereochemistry, were elucidated through spectroscopic analyses, quantum chemistry calculations, and single-crystal X-ray diffraction. Notably, the incorporation of pyrrole and indole moieties in peganines A–B, thiazole fragments in peganumals A–B, and a C-1 α,β-unsaturated ester motif in pegaharmine F (>5) are all rare, and their presence in the genus Peganum were demonstrated for the first time. All isolates were tested for antiproliferative activities against the HL-60, PC-3, and SGC-7901 cancer cell lines, and compounds >9, >11, >12, and >13 exhibited moderate cytotoxicity against HL-60 cancer cell lines with IC50 values in the range of 4.36–9.25 μM.