The biological activities of 4 medicinal plants (Acokanthera oppositifolia, Plantago lanceolata, Artemisia vulgaris and Conyza canadensis) were investigated. These plant extracts were subjected to screening for their possible effects as analgesic, and anti-inflammatory agents. The plant materials (only leaves were used in this study) were used in 4 solvents (acetone, ethyl acetate, chloroform and hexane). Plantago lanceolata hexane leaf extract inhibited cyclooxygenase-2 (COX-2) activity with an IC50 value of 0.41 μg/mL. Quercetin, positive control in this study inhibited COX-2 with a recorded IC50 = 8.39 μg/mL. However, the COX-1 inhibition by same extract indicated an IC50 of 68.99 μg/mL compared to the positive control (quercetin), whose activity was represented with an IC50 value of 4.6 μg/mL. The lipoxygenase assay indicated that Plantago lanceolata hexane extract and Acokanthera oppositifolia acetone extract were the most active samples with an IC50 of 4.75 μg/mL and 7.73 μg/mL. Plantago lanceolata hexane extract was the most active in all enzyme inhibitions, revealing the great potential it presents as a source of new anti-oxidative, analgesic and anti-inflammatory drugs, with less adverse effects.