Characterization of the essential oils from leaves of different sweet potato cultivars grown in Brazil

Sweet potato (Ipomoea batatas (L.) Lam.) leaves are commonly used as human foodstuff in some African and Asian countries. Scientific knowledge about the chemical composition and biological properties of these leaves is useful to allow humans to properly use this specific part of this plant. Thus, this study aimed to evaluate the chemical composition, antioxidant and toxicological potentials of the essential oils obtained from the leaves of four cultivars of sweet potatoes (Batata Roxa, IAPAR 69, Beni Imo and Batata-doce Japonesa) grown in Brazil. Essential oils were isolated by hydrodistillation (100°C, 4 hours) and their components were analyzed by GC/MS and GC/FID techniques. The antioxidant activities and the toxicological potentials of these essential oils were determined by ABTS and Artemia salina assays, respectively. Twenty-three compounds were found in these essential oils, with the sesquiterpene group being the major one. The compounds β-caryophyllene, β-copaene, γ-elemene, and β-elemene were found in concentrations of 1.08 – 28.63% of the essential oil among cultivars. β-Caryophyllene, α-caryophyllene, and δ-cadinene may explain the characteristic aroma of these essential oils. Their moderate antioxidant capacities demonstrated by the mean IC50(ABTS) value of (2.53 ± 0.27) mg mL−1 could be explained by the synergistic effects of α-cadinol, α-caryophyllene, γ-elemene, δ-cadinene, germacrene B, and phytol. The LD50(ASB) values (minimum: 0.60 ppm for cv. Beni Imo; maximum: 4.78 ppm for cv. Batata Roxa) are probably associated with δ-cadinene, α-cadinol, phytol, and α-caryophyllene. The high cytotoxicity attributed to this kind of essential oil shows that its use as a natural food preservative can be harmful to human health. The use of sweet potato leaves as a human foodstuff must be also considered with caution. As far as we are aware, no studies on the essential oils of these cultivars of sweet potato grown in Brazil were previously reported in the literature.