Racemic indole alkaloids from the seeds of Peganum harmala

Abstract Five pairs of new 2-oxoindole alkaloids, (±)-peganumalines A–E ( 1 – 5 ), and a new indole alkaloid, peganumaline F ( 6 ), along with two known analogues, were isolated from the seeds of Peganum harmala . Their structures and absolute configurations were elucidated through spectroscopic analyses and quantum chemistry calculations. Notably, (±)-peganumalines A ( 1 ) represent a pair of rare 2-oxoindole dimeric alkaloid enantiomer with the hitherto unknown carbon skeleton. All isolates were tested for antiproliferative and antibacterial activities.