Chemical Analysis and Antioxidant Activity of Essential Oils of Two Morphotypes of Lippia alba (Mill.) NE Br. ex Britton & P. Wilson (Verbenaceae)

Lippia alba (Mill.) N. E. Br. ex Britton & P. Wilson is an aromatic shrub of Verbenaceae family. L. alba exhibits variability among its different accessions, showing difference in morphology and in the composition of essential oil. The objective of this study was to chemically characterize and evaluate the antioxidant activity of essential oil of two L. alba morphotypes. The essential oils were isolated by hydrodistillation using a Clevenger apparatus and the identification was done through GC/GC-MS analysis. The antioxidant activity was evaluated using DPPH radical scavenging, Iron chelating activity, FRAP assay, Super oxide radical scavenging and Nitric oxide radical scavenging activity. More than eighty constituents were identified in both the oil's. Both the oils were characterized by a high amount of oxygenated monoterpenes (80.8 %) and (82.0 %). The major constituent in both the morphotypes was linalool. The other major constituents found in type-I were eucalyptol (4.2 %), neral (1.1 %), geranial (1.5 %), E-caryophyllene (3.1 %), germacrene-D (3.3 %), germacrene-B (1.6 %), 3E, 5E-2,6-dimethyl-3,5,7-octatriene-2-ol (2.1 %), 3E, 5Z-2,6-dimethyl-3,5,7-octatriene-2-ol (3.8 %) whereas in type-II were eucalyptol (4.7 %), beta-citronellol (1.3 %), neral (2.3 %), geranial (2.8 %), beta-caryophyllene (2.3 %), germacrene-D (3.0 %), germacrene-B (1.4 %), carryophyllene oxide (1.1 %), 3E, 5E-2,6-dimethyl-3,5,7-octatriene-ol (1.6 %), 3E, 5Z-2,6-dimethyl-3,5,7-octatriene-2-ol (2.9 %). Both the morphotypes exhibited good antioxidant activity but the activity, was found higher in type-II L. alba morphotype than type-I. The chemical composition and antioxidant activity suggest L. alba as a potential source of natural linalool and further its use in ethanopharmacological applications.