Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of the bacterium Staphylococcus aureus characterized by its multi-drug resistance to penicillins, clindamycin, tetracyclines, macrolides, aminoglycosides, fluoroquinolones, etc. Chromolaena odorata R.M. King & H. Rob is a potential and promising plant that should be explored for the management of diseases caused by MRSA because its fractions have anti-MRSA activities. Objective: The aim To screen and identify the chemical constituents of the anti-MRSA fractions of C. odorata leaves. Materials and Methods: Seven isolates of MRSA and methicillin-susceptible S. aureus (MSSA) and a control strain S. aureus NCIBB 8588 were used for this study. Fresh leaves of C. odorata were collected from Igbinedion University, Okada environs, Edo State, Nigeria. The fractions obtained were analyzed with a Gas Chromatography-Mass Spectrometry (GC-MS) analyzer to identify their chemical constituents. Results: A total of eight fractions (F1, F2, F3, F4, F5, F7, F8, F9) obtained from the leaves of C. odorata were analyzed for their chemical constituents. They contain essential oils which were: α-pinene, β-pinene, 1,8-cineole, σ-elemene, terpineol, camphene, cymene, linalool, terpinolene and α-phallandrene. Free fatty acids were also identified: namely, hexanoic acid (caproic acid), dodecanoic acid (lauric acid), decanoic acid (capric acid) and octanoic acid (caprylic acid). Constituents common in fractions F2 and F3 with the highest anti-MRSA activities were: α-pinene, camphene, octanoic acid and decanoic acid. Conclusion: C. odorata is a promising anti-MRSA agent that can be explored for the synthesis of novel drugs for use in the treatment of MRSA infections
