Synthesis of magnetic iron oxide nanoparticles using pulp and seed aqueous extract of Citrullus colocynth and evaluation of their antimicrobial activity.

Objectives: Citrullus colocynth (CTC) is a wild medicinal plant with proven antimicrobial activity. The aim of this study is to investigate the use of its aqueous extract in producing magnetic iron oxide nanoparticles (MNPs) with improved antimicrobial activity. The cold and hot aqueous extract of seed and pulp parts of CTC, respectively, were used to produce MNPs. The particles were characterized by transmission electron microscope, energy dispersion x-ray, FTIR and their surface charge were measured. The antimicrobial activity of the produced particles was assessed against two Gram positive (Bacillus subtillis and Staphylococcus aureus) and two Gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and well as against Candida albicans.

Results: MNPs synthesized using cold seed extract (S-MNP) and pulp extract (P-MNP) were spherical in shape. The size distribution was more uniform in the S-MNP (6-15 nm) compared to the P-MNP (12-45 nm). Both particles showed comparable anti-microbial potential against the tested microorganisms. At a concentration range of 0.48-1000 μg/mL, S-MNP inhibited bacterial growth by 16.0-99.0% and 10.0-91.0%; while P-MNP inhibition was 11.0-100.0% and 11.0-99.0% for Gram positive and negative bacteria; respectively. Candida albicans was the least affected microorganism with maximum inhibition of 63-88% after treatment with S-MNP and P-MNP (1 mg/mL), respectively.

Conclusions: The aqueous extract of CTC can be used for synthesis of MNPs with antimicrobial activity. The described procedures are simple and can be modified for large scale green synthesis of MNPs.