Mohammad Nazrul Islam Bhuiyan*, Meher Nahid
Cosmos is an aromatic plant with Essential Oils (EOs) used in food, flavouring, and medicine. A comparative investigation of the chemical composition and antimicrobial activities of the leaf EOs of Cosmos bipinnatus Cav. (cultivated) and Bidens ferulifolia (Jacq.) (wild) from Bangladesh has been conducted, whereas the composition of wild EO is being studied for the first time. Both EOs were extracted using the hydro distillation method, and the chemical composition of both EOs was identified by Gas Chromatography–Mass Spectrometry (GC-MS). The antimicrobial activity of cultivated EO was tested against ten pathogenic bacteria and six pathogenic fungi using the disc diffusion method. Even at 2 g disc-1, cultivated EO was able to inhibit all of the test microorganisms from growing. The value of EO was evaluated for the minimum inhibitory concentration (MIC, 100-300 ppm) and minimum bactericidal concentration (MBC, 200-400 ppm). At 100 ppm, all of the test fungi had 100% of their radial mycelial growth stopped by essential oils. The Minimum Fungicidal Concentration (MFC) was between 50 and 300 ppm, and the Minimum Inhibitory Concentration (MIC) was between 200 and 400 ppm. The wild-type EO contained (Z)-β-ocimene (28.76%), germacrene D (19.19%), 2,6-dimethyl-1,3,5, -octatetraene, E.E (17.12%), caryophyllene (5.40%) and elixene (4.64%), whereas the cultivated type confirmed (Z)-β-ocimene (48.29%), trans-3-caren-2-ol (19.21%), sabinene (9.36%), germacrene D (6.10%) and β-pinene (4.18%). The main constituent (Z)-β-ocimene has a 40% higher content in the cultivated type than the ‘wild’ type. The cultivated type of Cosmos EO has promising antimicrobial activities.