Most species of the genus Laggera are often used in traditional and folk medicines for the treatment of jaundice, inflammation, leukemia, removing phlegm, bronchitis and bacterial diseases. The essential oils obtained from Laggera plants are rich sources of oxygenated monoterpenes and sesquiterpenes. Among oxygenated monoterpenes, aromatic ether 2,5‐dimethoxy‐p‐cymene is the most abundant and dominant compound of many essential oils of the Laggera species. Till today, to the best of our knowledge, chemical compounds of the essential oils and/or extracts of only eight Laggera species were reported from different countries. Thus, this review presents the chemical compositions and biological activities of the essential oils of these plants studied in thirteen countries. In addition, it discusses the reported ethnobotanical and ethnopharmacological information as well as biological activities of the extracts and some of the isolated compounds of Laggera plants species.

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Laggera tomentosa Sch. Bip. ex Oliv. et Hiern (Asteraceae), an endemic Ethiopian medicinal plant is traditionally used to treat various ailments. Previously, the chemical constituents of the essential oil (EO) of its leaves and inflorescence were documented. However, no data about chemical compositions of other parts EOs of the plant have been reported up to date. Moreover, there is no previous biological activity report on any parts EOs of this plant. Thus, in this study, the EOs were isolated from the stem barks and roots of this plant by hydrodistillation and analyzed using GC-MS to identify their components. In addition, antibacterial potentials of the oils were evaluated by disc diffusion and minimal inhibitory concentration methods. DPPH and H2O2 methods were also employed to assess their antioxidant properties. Oxygenated monoterpenes (71.82 and 77.51%), of which 2,5-dimethoxy-p-cymene (57.28 and 64.76%) and thymol methyl ether (9.51 and 8.93%) were identified as major components in EOs of stem barks and roots of L. tomentosa and the oils were the most potent in DPPH (IC50, 0.33 ± 1.10 and 0.39 3 ± 0.97 mg/mL) assay, respectively. Moreover, the EOs demonstrated appreciable activity towards the Gram positive (S. aureus and B. cereus) bacteria. Among these oils, the oil of the stem barks showed the greatest activity to the Gram positive (MIC = 0.625 mg/mL) bacteria. Therefore, the overall results suggest that EOs of L. tomentosa may have promising prospect for pharmaceutical, food and other industrial applications.

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