Structurally Diverse Alkaloids from the Seeds of Peganum harmala

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.