Antimicrobial activity of Strobilanthes crispus leaves aqueous extract and green biosynthesis iron oxide nanoparticles against selected human pathogens

Strobilanthes crispus is a plant species from the family of Acanthaceae, known as ‘pecah kaca’ or ‘jin batu’ among Malaysians. S. crispus have medicinal properties that are anti-diabetic, diuretic, laxative, antimicrobial and wound healing properties. The study aimed to investigate the antimicrobial activity of S. crispus leaves aqueous extract and iron oxide nanoparticles (IONP) against the selected human pathogens namely Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Bacillus cereus ATCC 11778, Salmonella typhi ATCC 14028, Candida albicans ATCC 10231 and Aspergillus niger ATCC 16404. The antimicrobial properties of S. crispus leaves aqueous extract and IONP was measured through the disc diffusion test. The inhibitory action of S. crispus leaves aqueous extract was only visible against E. coli; at 25 mg/ml with mean diameter zone of inhibition was 7.3 ± 0.017 mm and at 50 mg/ml (8.7 ± 0.017 mm). However, IONP was able to show better antimicrobial activity against all selected human pathogens compared to S. crispus leaves aqueous extract. The largest mean diameter zone of inhibition exhibited was 11.50 ± 0.288 mm at 0.2 M IONP and 9.00 ± 0.577 mm at 0.3 M IONP against S. aureus. The properties and structural of IONP was investigated through UV-Vis, SEM, XRD and FTIR method. Hence, these data concluded that S. crispus leaves aqueous extract and IONP have antimicrobial properties against selected human pathogens thus act as potential antimicrobial agent in pharmaceutical industry.