Psidium guajava and Carthamus tinctoirus are cultivated in many countries of the world. The study aimed to evaluate the antibacterial activity of P. guajava and C. tinctoirus extracts against a bacterial causative agent of respiratory tract infection. Experimental study was conducted in Khartoum, Sudan from April to June 2013. In the present study, P. guajava and C. tinctoirus extracts were tested for antibacterial activity against various isolated and standard bacteria. A total of four bacteria (Klebsiella pneumonia, Pseduomonas aeruginosa, Staphylococcus aureus, Streptococcus pyogenes and Klebsiella pneumonia ATCC53657, Pseduomonas aeruginosa ATCC27853, Staphylococcus aureus ATCC 25923, Streptococcus pyogenes, ATCC26722) were identified at Department of Microbiology, Omdurman Islamic University, Sudan. The two plants used in this study were collected from Gazira State (P. guajava from Al. kasamber by the author, C. tinctoirus from Al- sharafa El- baher by Dr.El. Taher Ahmed, Faculty of Agriculture, Gazira University, Sudan). They were authenticated by Ustaz Om Al–kheer and Nadia: staff in Medicinal and Aromatic Plants Research Institute (MAPRI). 100 g of each plant (leaves or seeds) sample were powdered by grinder and extracted as described. Six different extracts were prepared by Soxhelt using standardized protocols (using petroleum ether, boiled distilled water and methanol). All the extracts were tested for antibacterial activity by cup- plate agar diffusion method (0.1 ml/ cup). The methanolic extract of P. guajava leaves and C. tinctorius seeds were more active than aqueous and petroleum ether of both plants against tested microorganisms. P. guajava had high activity (MDIZ = 12.5 - 25.5 mm), whereas C. tinctorius was less effective (MDIZ = 11.5 - 15 mm) than the drugs used. Moreover, P. guajava leaves extract were more effective than the used antibiotic drugs. All the extracts exhibited significant antibacterial activity. Maximum antibacterial activity was found in the methanolic extracts. The present study reflects the chemotherapeutic and justified traditional use of P. guajava and C. tinctoirus.

Keywords: Psidium guajava, Carthamus tinctoirus, antibacterial activity, extracts.