Eugenia calycina species belongs to Myrtaceae family and it is known as pitanga of the Cerrado or red pitanga. This family is characterized by the predominance of sesquiterpenes which have biological activities such as antimicrobial, anti-inflammatory and antirheumatic1. In recent studies, the essential oil from leaves of E. calycina showed antibacterial activity against P. gengivalis and P. nigrescens2. In other studies, more than 60% of essential oil extracted from 361 plant species presented larvicidal activity against Aedes aegypti3. This work describes the isolation and identification of sesquiterpenes from leaves of E. calycina and their larvicidal activity against Aedes aegypti. Leaves (120 g) were collected in Uberlândia (Minas Gerais, Brazil) and the essential oil was extracted by hydrodistillation for 4 h using a Clevenger apparatus. The yield of this process was 0.39%. Isolation of compounds was performed using column chromatography (30 cm high/3 cm in diameter) with silica gel (25 g) as stationary phase and dichloromethane and ethyl ether as gradient elution chromatography. Three compounds were isolated and characterized by NMR 1H and 13C: 4β,10α-aromadandrene diol (1) (22 mg) and 1β,11-dihydroxy-5-eudesmene (2) (16 mg), that first time identified in E. calycina; and spathulenol (3) (56 mg).
The larvicidal activity was performed in quadruplicate using disposable cups (50 mL) with 10 larvae in 20 mL of oil solution in dechlorinated water with DMSO (1.25%). The following concentrations were tested: 500, 250, 125, 62.5, 31.25 and 15.625 μg mL-1. Dechlorinated water with DMSO (1.25%) was used as negative control and Bt-Horus®SC was used as positive control. The LC50 of the essential oil obtained were 195.3, 166.5 and 148.7 μg mL-1 at 24, 48 and 72h, respectively. Komalamisra et al.4 considered products showing effectiveness activity with LC50 between 100 and 750 μg mL-1. Thus, the evaluated essential oil presents effectiveness activity. According to Silva et al.5, the essential oil of leaves of Eugenia brojoensis showed mainly sesquiterpenes and presented LC50 214.7 μg mL-1, being an alternative as a natural insecticide in Aedes control. Likewise Eugenia melanadenia and Psidium rotundatum exhibit LC50 220 and 164 μg mL-1, respectively6. Larvicidal assay of isolated compounds were tested at 25 and 100 μg mL-1, but they were inactive at these concentrations. Through, in this study was possible to isolate and to characterize new sesquiterpenes. Besides the essential oil showed effective larvicidal activity and it can be used as bioinsecticide in the control of Aedes aegypti larvae.
Acknowledgements: IQUFU, CAPES, CNPq, FAPEMIG and Enviromental Watch Division.
References: ¹Stefanello, M.E.A. et al. Chem Biodivers. 8, 73-89, 2011; 2Sousa, R.M.F. et al. Ind Crops Prod. 65, 71-78, 2015; 3Dias, C.N. et al. Parasitol Res. 113(2), 565-592, 2013; 4Komalamisra, N. et al. Southeast Asian J Trop Med Public Health. 36(6), 1412-1422, 2005; 5Silva, A.G. et al. Journal of Essential Oil Bearing Plants. 18(6) 1441-1447, 2015; 6Aguilera, L. et al. Rev Cubana Med Trop. 55(2) 101-104, 2003.