Composition of Essential Oils and Ethanol Extracts of the Leaves of Lippia Species: Identification, Quantitation and Antioxidant Capacity

The principal components of essential oils, obtained by steam-hydrodistillation from the fresh leaves of five species of the genus Lippia, namely Lippia gracilis AV, Lippia sidoides Mart, Lippia alba carvoneifera, Lippia alba citralifera and Lippia alba myrceneifera and ethanol extracts, were evaluated. The greater antioxidant capacity (IC50 = 980 ?g/mL; p < 0.05), assessed by the HPLC-based hypoxanthine/xanthine oxidase assay, was determined in the essential oil obtained from Lippia alba carvoneifera, while the remainder were comparatively inactive (IC50 > 2000 ?g/mL). Major compounds in the oils were, thymol (Lippia sidoides Mart, 13.1 g/k), carvone (Lippia alba carvoneifera, 9.6 g/kg), geranial (Lippia alba citraleifera, 4.61 g/kg; Lippia alba myrceneifera, 1.6 g/kg), neral (Lippia alba citraleifera, 3.4 g/kg; Lippia alba myrceneifera, 1.16 g/k), carvacrol (Lippia gracilis AV, 5.36 g/kg)and limonene (Lippia alba carvoneifera, 5.14 g/kg). Of these, carvone (IC50 = 330 ?M)along with thymol (1.88 units), and carvacrol (1.74)units, were highly active in the hypoxanthine/xanthine oxidase, and ORAC assays respectively. The following compounds namely 1: calceolarioside E, 2: acteoside, 3: isoacteoside, 4: luteolin, 5: 5,7,3´,4´-tetrahydroxy-3,6-dimethoxy flavone (spinacetin), 6: naringenin, 7: apigenin, 8: 6-methoxy apigenin (hispidulin), 9: 5,7,3´-trihydroxy-3,6,4´-trimethoxy flavone, 10: 5,7,4´-trihydroxy-3,6-dimethoxy flavone, 11: naringenin-4´-methyl ether, 12: 5,7-dihydroxy-3,6,4´-trimethoxy flavone (santin), 13: 5,7-dihydroxy-6,4´-dimethoxy-flavone (pectolinaringenin)and 14: 5-hydroxy-3,7,4´-trimethoxy flavone were identified in the ethanol extracts. Of the leaf ethanol extracts, strong antioxidant capacity was only evident in that of Lippia alba carvoneifera (IC50 = 1.23 mg/mL). Overall, the data indicates that use of the leaves of Lippia species in food preparations, should be beneficial to health.