Antioxidant and free radical scavenging activities of essential oils

Reactive oxygen and nitrogen free radicals are produced during immune activity, and are triggered by several environmental factors such as pollution, smoke, and sunlight. Harmful effects of these reactive species include cellular damage to RNA, DNA, proteins and lipids. In humans several diseases including those connected with the heart, lung, and the eye are associated with the accumulation of reactive oxygen and nitrogen species (ROS/RNS). Antioxidants in blood, cells, and tissue fluids play an important role in neutralizing the normal level of oxidative damage caused by these free radicals. In an effort to minimize the impact of environmental pollution on humans, identification of natural product antioxidants has become a realistic and powerful tool in the dietary and natural products industry.

248 essential oils belonging to 18 botanical families of medicinal, herbal and wild flora as well as 2 mammalian essential oils were evaluated for their antioxidant and ROS/RNS radical scavenging activities using high performance thin layer chromatography/bioautography (HPTLC) and the DPPH (2,2-diphenyl-picrylhydrazyl) assay.

Seven percent of the tested essential oils were found to have very high antioxidant activity; these were further fractionated by HPTLC and their chemical composition was identified using gas chromatography/mass spectrometry.

The majority of the active samples showed no more than one or two spots in their TLC indicating that antioxidant activity is only associated with certain type of chemicals. Identified active compounds were found to be oxygenated monoterpenoids, monoterpene hydrocarbons as well as monoterpene phenols.