en اتنوفارماکولوژی Ehtnopharmacology پژوهشي Original Research <div style="text-align: justify;"><strong>Background</strong>: The growing threat of antimicrobial resistance has intensified the search for alternative therapies using natural sources. Guiera senegalensis, a medicinal shrub widely used in African traditional medicine, has shown promising antimicrobial properties due to its rich phytochemical content.&nbsp;<br> <strong>Objectives</strong>: This study evaluated the phytochemical composition and the in vitro antibacterial and antifungal activities of the methanolic leaf extract of G. senegalensis against selected bacterial isolates.<br> <strong>Methods</strong>: Fresh leaves of G. senegalensis were collected, shade-dried, and extracted by maceration in 70% methanol for 72 hours. Phytochemical testing was conducted using standard qualitative methods. Antibacterial activity was assessed using the agar disk diffusion method on Mueller-Hinton agar, while antifungal activity was evaluated using the agar well diffusion method on potato dextrose agar (PDA). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution and tube dilution methods, respectively.<br> <strong>Results</strong>: Phytochemical testing revealed the presence of flavonoids, tannins, saponins, glycosides, and steroids, while alkaloids were absent. Antimicrobial activity was concentration-dependent, with E. coli and S. aureus showing the highest bacterial susceptibility (zones of inhibition up to 29 mm) and F. oxysporum exhibiting strong antifungal sensitivity (zone of inhibition= 25 mm at 500 mg/mL). MIC values ranged from 31.25 to 125 mg/mL for bacteria and fungi, while MBC values ranged from 62.5 to 250 mg/mL.<br> <strong>Conclusion</strong>: The methanolic leaf extract of G. senegalensis demonstrated high antibacterial and antifungal activity, particularly against gram-positive bacteria and filamentous fungi, supporting its potential as a natural antimicrobial agent.</div> Guiera senegalensis, antimicrobial activity, antifungal, antibacterial, bacterial isolates 179 186 http://pbr.mazums.ac.ir/browse.php?a_code=A-10-1329-2&slc_lang=en&sid=1 Albashir Tahir albashirtahir@sazu.edu.ng 0000-0001-9272-5540 Yes Department of Pharmacology, Faculty of Basic Medical Sciences, Sa’adu Zungur University, Bauchi, Nigeria. Aishatu Sani Muhammad ayshart03@gmail.com No Department of Pharmacology, Faculty of Basic Medical Sciences, Sa’adu Zungur University, Bauchi, Nigeria. Gideon Makeri Ayuba ayubagideon2020@gmail.com No Department of Pharmacology, Faculty of Basic Medical Sciences, Sa’adu Zungur University, Bauchi, Nigeria. Al-ameen Abubakar Saeed alameenabubakar571@gmail.com No Department of Pharmacology, Faculty of Basic Medical Sciences, Sa’adu Zungur University, Bauchi, Nigeria. Aminu Samaila Lassi aslassi@sazu.edu.ng No Department of Public Health, Faculty of Allied Health Sciences, Abubakar Tafawa Balewa University, Bauchi, Nigeria. Khadija Abdullahi Kobi kakobi@atbu.edu.ng No Department of Nursing, Faculty of Allied Health Sciences, Abubakar Tafawa Balewa University, Bauchi, Nigeria. Nazif Yakubu nazifyakubu@gmail.com No Department of Microbiology, Faculty of Sciences, Sa’adu Zungur University, Bauchi, Nigeria. Saddam Ahmad ahmadsaddam554@gmail.com No Department of Pharmacology, Faculty of Basic Medical Sciences, Sa’adu Zungur University, Bauchi, Nigeria.