Isolation and characterization of the alkaloid Nitidine responsible for the traditional use of Phyllanthus muellerianus (Kuntze) Excell stem bark against bacterial infections.

Phyllanthus muellerianus (Kuntze) Excell (family Euphorbiaceae) stem bark methanol extract inhibited the growth of Clostridium sporogenes and Streptococcus pyogenes, responsible for gas gangrene and suppurative and non suppurative diseases, respectively. After the HPLC fingerprint acquisition a bioguided fractionation of the defatted methanol extract allowed the isolation of six fractions whose activity was evaluated against the two pathogen bacteria. A further purification of the most active fraction afforded a pure compound responsible for the very interesting inhibitory activity against C. sporogenes and S. pyogenes (MIC 0.91 μM, MIC 3.64 μM). (1)H NMR and MS analytical techniques allowed the identification of the bioactive as Nitidine; this quaternary ammonium alkaloid was observed in the genus Phyllanthus for the first time. A study on Nitidine counter ion, performed using energy dispersive spectroscopy (EDS) coupled with scanning electron microscopy (SEM) was also carried out.