Phytochemical composition of essential oils from aromatic plants inherited with bioherbicidal activity in arabica coffee production system of Ethiopia

Essential (EOs) can be considered as an alternative tool to control weeds, as they are eco-friendly and safe bioherbicides. Based on their herbicidal efficacy against coffee weeds in the prescreening under in-vitro, lath-house and field experimentations, five aromatic plants namely, Cymbopogon citratus, C. martinii, C. winterianus, Eucalyptus citriodora and Thymus schimperi were selected to identify their chemical composition using Gas Chromatography-Mass Spectrometry. The chromatographic analysis revealed the presence of 45 compounds in C. citratus oil dominated with citral (84.86%) from the subclasses of trans-Citral and cis-Citral. Thirty-three compounds were fractionated and identified in C. martinii oil containing geraniol (55.27%), trans-Geranyl acetate (16.82%), (6R,7R)-Bisabolone (7.23%) and trans-.beta.-Ocimene (6.18%) as the main inherited components. The EO from C. winterianus contained 47 compounds with citronellal (31.31%), geraniol (21.24%), citronellol (12.06%) and elemol (6.68%) as the major component. Similarly, a total of 52 compounds were identified from the EO of E. citriodora containing two major compounds namely, citronellal (76.93%) and citronellol (15.24%). The EO from T. schimperi were composed of 32 compounds with carvacrol (72.55%) and thymol (9.12%) as the main constituents. The present finding indicated that herbicidal activities of the EOs might be attributed to their fingerprint components such as citral (3,7-dimethylocta-2,6-dienal), geraniol (2E)-3,7-dimethylocta-2,6-dien-1-ol), citronellal (3,7-dimethyloct-6-enal), citronellol (3,7-Dimethyloct-6-en-1-ol), carvacrol (2-methyl-5-propan-2-ylphenol) and thymol (5-methyl-2-propan-2-ylphenol). Therefore, these bioactive agents have the potential to be used as herbicides to manage weed species in coffee farms for the future.