Abstract
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 the chemical compositions of other parts of the EOs of the plant have been reported to date. Moreover, there are no previous biological activity reports on any parts of the EOs of this plant. Thus, in this study, the EOs were isolated from the stem bark and roots of this plant by hydrodistillation and analyzed using gas chromatography-mass spectrometry to identify their components. In addition, antibacterial potentials of the oils were evaluated using the disc diffusion and minimal inhibitory concentration (MIC) methods. 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide 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 the EOs of stem bark and roots of L. tomentosa and the oils, were the most potent in the DPPH (IC50, 0.33 ± 1.10 and 0.39 ± 0.97 mg/mL) assay, respectively. Moreover, the EOs demonstrated appreciable activity towards the gram+ ( S. aureus and B. cereus ) bacteria. Among these oils, the oil of the stem bark showed the greatest activity to the gram+ (MIC = 0.625 mg/mL) bacteria. Therefore, the overall results suggested that the EOs of L. tomentosa may be a promising prospect for pharmaceutical, food, and other industrial applications.
Highlights
Composition of the essential oils EOs and their constituents are widely used in the food, pharmaceutical, and cosmetics industries [17]
The chemical names of the identified constituents of the EOs isolated from the stem bark and roots of L. tomentosa, together with their retention indices (RIs) and percentages, are given in Table 1, where the compounds have been listed in the order of elution on the DB-5 column used
The results indicated the susceptibility of the gram+ bacteria to the EOs
Summary
Most of its species are often used in folk and traditional medicines for the treatment of inflammation, jaundice, leukemia, bronchitis, removing phlegm, and bacterial diseases, and their leaves, as well as aerial parts, have been reported to have antiinflammatory, antibacterial, antiviral, antioxidant, hepatoprotective, insecticidal, antifungal, anthelmintic, sedative, antituberculosis, and antidiarrheal properties [2]. The essential oils (EOs) of Laggera species have been reported to exhibit antibacterial, antifungal, antioxidant, larvicidal, and insecticidal activities [3,4,5]. The chemical constituents of the extracts and/or EOs of only 8 plants of the genus Laggera have been reported from 13 countries [2]. To the best of our knowledge, and according to a literature survey, no data about the chemical compositions of other parts of the EOs of the plant have been reported to date. The antioxidant and antibacterial potentials of the oils, which may be useful in foods, pharmaceuticals, and other industries, were assessed and reported
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