A review article on the antimicrobial and antioxidant essential oils of aromatic plants in Ethiopia

Introduction

Ethiopia has eight vegetation types across altitudes (< 400 - 4533 m). Consequently, it is biologically rich (> 6500–7000 plant species) with 12–19% endemicity. While medicinal plant knowledge in Ethiopia is partially documented, much remains unexplored. This study reviews the essential oils (EOs) of aromatic plants in Ethiopia, known for their antimicrobial and antioxidant properties.

Methods

From November to December 2022, we retrieved 28 studies from PubMed/Medline, Science Direct, SciVerse, Web of Science, and Google Scholar using boolean operators and terms such as ‘essential oil,’ ‘biological activities,’ ‘bioactivy,’ ‘antioxidant activities,’ ‘antibacterial activities,’ ‘antifungal activities,’ ‘antimicrobial activities,’ and ‘Ethiopia.’

Results

Promising antibacterial EOs include Mentha aquatica, Apium leptophyllum, Citrus reticulata, Mentha arvensis, Mentha longifolia, Mentha piperita, Mentha spicata, Olea europaea, Otostegia integrifolia, Phytolacca dodecandra, Plectranthus marrubatus, Salvia nilotica, Salvia officinalis, and Salvia schimperi (MICs < 0.005 to 0.064 mg/mL). For antifungal activity, notable EOs include Acokanthera schimperi, Cinnamomum zeylanicum, C. reticulata, C. reticulata, O. europaea, O. integrifolia, P. dodecandra, P. marrubatus, Satureja paradoxa, and Thymus schimperi (MICs < 1 mg/mL). Antioxidant essential oils were those of Artemisia absinthium L., Artemisia abyssinica, Artemisia afra, Coriandrum sativum, Curcuma domestica, Juniperus procera, Lippia adoensis, Ocimum basilicum, O. europaea, Rosmarinus officinalis, S. officinalis, Satureja abyssinica, and S. paradoxa. The IC₅₀ of all these essential oils was < 0.05 mg/mL.

Conclusion

The present review identified the EOs of many Ethiopian aromatic plants with promising antimicrobial and antioxidant activities that demand more enquiry for preclinical testing, and eventually, clinical applications.