Jawaher Ebrahim Rashid Alaleeli
Antibiotic Activity of Rosemary Plant (Rosmarinus officinalis) Extract Against Multi-Antibiotic-Resistant Bacteria
This study aimed to optimise the extraction of rosmarinic acid (RA) from UAE-grown rosemary (Rosmarinus officinalis) and evaluate the antibacterial activity of rosemary crude extract against antibiotic-resistant bacteria. The fresh rosemary leaves from Umm Al Quwain, UAE were extracted by 70% ethanol, and the RA was determined using the UV-Vis absorption spectrum over the wavelength range of 200–450 nm and identifying the maximum absorbance peak at 330 nm. Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli were chosen as the local isolates and ATCC strains (K. pneumoniae ATCC 13883, P. aeruginosa ATCC 27853 and Escherichia coli ATCC 25922) were tested by disk diffusion technique and agar well diffusion methods. The moisture content and optimum extraction time for maximum RA-equivalent recovery from the fresh leaves of rosemary leaves were 85.27% and 45 minutes, respectively. Two successive extraction cycles were sufficient to recover 86.42% of RA. Dried rosemary leaves yielded higher RA-equivalent content (7.67 mg/g dry weight) compared to fresh leaves (7.03 mg/g dry weight). All local K. pneumoniae and E. coli isolates were resistant to ampicillin but susceptible to imipenem, ceftriaxone and ciprofloxacin. The local P. aeruginosa isolate was susceptible to ciprofloxacin and showed intermediate susceptibility to imipenem. There was no inhibition of the tested local isolates with rosemary crude extract and pure RA. Weak inhibition was observed against K. pneumoniae ATCC 13883 and P. aeruginosa ATCC 27853 in disk diffusion method, with inhibition zones of 11.19–12.30 mm and 8.25–9.24 mm, respectively. Combination testing showed that neither crude extract nor pure RA enhanced antibiotic activity, as inhibition zones were smaller than those produced by antibiotics alone. Using the agar well diffusion method, crude rosemary extract showed clear inhibition zone of (22.98–26.58 mm) and (14.48–19.49 mm) and 12.38 mm against P. aeruginosa ATCC 27853, K. pneumoniae ATCC 13883 and local P. aeruginosa respectively.
