Chemical composition and antibacterial properties of Peganum harmala L.

The present study was conducted to investigate antibacterial properties of fruit and flower of Peganum harmala.

Column chromatography, followed by preparative thin layer chromatography (TLC) was used for final purification. The structure of pure alkaloids was determined using spectroscopic methods (¹H-NMR, ¹³C-NMR, UV and MS). Smoke and extract of total alkaloids were investigated for antimicrobial activity against five different microorganisms (standards and hospital isolates). The antibacterial activity was evaluated using disc diffusion assay and minimum inhibitory concentration (MIC) was determined by serial dilution methods.

Chemical investigation of the chloroform extract of ripe fruit and flower of P. harmala led to identification of three alkaloids in ripe fruit and two alkaloids in the flower and leaves of this plant. Alkaloids identified in ripe fruit were harmine, peganine (vasicine) and harmaline. Two alkaloids, harmine and peganine, were detected in the flower of P. harmala, while harmaline was only found in the ripe fruit. The total alkaloids of flower were compared with total alkaloids of ripe fruit by TLC method. Fruits and flowers had 3.12 and 3.27% alkaloid contents, respectively.

Our results showed that the alkaloids and smoke were specifically more effective on Candida albicans and Gram- positive bacteria (Micrococcus luteus and Staphylococcus aureus), while Gram- negative bacteria, especially Pseudomonas aeruginosa, were less sensitive.