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

摘要

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 (IC 50 = 980 μg/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 (IC 50 2000 μg/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 (IC 50 = 330 μM) 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 I: calceolarioside E, II: acteoside, III: isoacteoside, IV: luteolin, V: 5,7,3′,4′-tetrahydroxy-3,6-dimethoxy flavone (spinacetin) , VI: naringenin, VII: apigenin, VIII: 6-methoxy apigenin (hispidulin), IX: 5,7,3′-trihydroxy-3,6,4′-trimethoxy flavone , X:5,7,4′-trihydroxy-3,6-dimethoxy flavone , XI: naringenin-4′-methyl ether, XII: 5,7-dihydroxy-3,6,4′-trimethoxy flavone (santin) , XIII:5,7-dihydroxy-6,4′-dimethoxy-flavone (pectolinaringenin) and XIV: 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 (IC 50 = 1.23 mg/mL). Overall, the data indicates that use of the leaves of Lippia species in food preparations, should be beneficial to health.