Essential oils from Smyrnium olusatrum and their major components as potential mosquitocidal and trypanocidal agents

Smyrnium olusatrum L., also known as Alexanders or wild celery, is a celery-scented biennial herb belonging to the Apiaceae family and distributed in the Mediterranean area where it grows on hedgerows, hedged banks, sea cliffs, quarries and railway embankments, from sea level to 800 m of altitude [1]. Since Roman age the plant has been used as both a vegetable and for medicinal uses. After a long period of cultivation, the use of S. olusatrum was abandoned due to the introduction of common celery (Apium graveolens L.) in the Middle Ages [1]. Owing to the abundance of secretory structures like ducts and vittae [2], S. olusatrum is a rich source of essential oils. Their chemical composition has been extensively investigated by our group [1-4] and revealed the furan ring-containing sesquiterpenes as the marker compounds. Among the main compounds, isofuranodiene, germacrone and 1β-acetoxyfurano-4(15)-eudesmene were the most representative ones (Fig. 1). Recently, essential oils have been considered as new therapeutic options to combat protozoal infections [5] as well as effective and eco-friendly tools to control highly invasive mosquito vectors [6,7]. On this basis, we have assayed the S. olusatrum essential oils and its main components (i.e. isofuranodiene, germacrone and 1β-acetoxyfurano-4(15)-eudesmene) for larvicidal effects on Culex quinquefasciatus, the vector of lymphatic filariasis, and for inhibitory effects on Trypanosoma brucei, the protozoan parasite responsible for Human African trypanosomiasis. The essential oil of S. olusatrum flowers exhibited acute toxicity on C. quinquefasciatus larvae, with germacrone and isofuranodiene being involved in the effect displayed. As concerning T. brucei, the S. olusatrum essential oils showed good inhibitory effects and selectivity, with the sample from fruits being the most active, and isofuranodiene and 1β-acetoxyfurano-4(15)-eudesmene as the main contributors to the effect on protozoal cell. These results, although preliminary, encourage further studies in the attempt to find a new application of S. olusatrum secondary metabolites as natural insecticides and antiprotozoal agents.