Prosopis cineraria, Prosopis juliflora and Acacia tortilis are widely distributed plants in UAE. They have beneficial uses in traditional medicine and animal fodder. The exploration of these plants is of potential value to UAE economy through their large-scale utilization. The leaves of these plants were collected to study their main antimicrobial constituents. This study highlights the potential utilization of these plants leaves as antimicrobial agents. The aim is to explore the antimicrobial activity of P. cineraria, P. juliflora and A. tortilis.

Materials and Methods: Dried Leaves of above plants extracted with aqueous ethanol. Extracts subjected to phytochemical screening and thin layer chromatographic (TLC) separation to determine compounds present. Antimicrobial activity tests done for the extracts and fractions obtained by preparative TLC.

Results: Tannins constitute the major compounds in all three plant extracts. A TLC solvents system was developed for separation of the phytochemical constituents in the three aqueous plant extracts. Prosopis juliflora aqueous extract presented the highest activity against all tested microorganisms at a concentration of 5mg dry leaf material/disc, inhibition zones exhibited by P.juliflora were as follows: ZoI (23mm) against Eschericha coli, ZoI (18mm) against Staphylococcus aureus and ZoI (12mm) against Candida albicans. Isolated fraction 1 from P.juliflora aqueous extract, containing two major spots, exhibited intermediate activity followed by fraction 3, fraction 2 had no activity.

Conclusions: P. juliflora leaves revealed significant antimicrobial activity. It is potential for treatments of infectious diseases. The developed TLC solvent system may further be applied on column chromatographic separation of pure active compounds from P. juliflora.

Keywords: P. juliflora, P. cineraria, A. tortilis, UAE, Antimicrobial activity

Key message: Prosopis juliflora aqueous extract presented the highest activity against all tested microorganisms at a concentration of 5mg/disc. Therefore, P. juliflora has a potential value to be utilized for infectious diseases treatment.