Evaluating Essential Oils in Cosmetics: Antioxidant Capacity and Functionality

Skin constantly is exposed to environmental oxidative stressors such as ultraviolet radiation (UVR), air pollutants, chemical oxidants and aerobic microorganisms.1, 2 Reactive oxygen species (ROS) are considered major contributors to skin aging, cancer and certain skin disorders3 since they react negatively with DNA, proteins and unsaturated fatty acids.4 In addition, while healthy skin possesses an innate antioxidant defense system, ROS and other free radicals or excessive free radical attack can overwhelm the cutaneous antioxidant capacity, depleting the skin’s antioxidants and damaging biomolecules such as lipids, proteins and nucleic acids. This further leads to oxidative damage, skin cancer, immunosuppression and premature skin aging. Therefore, supplying exogenous antioxidants topically to the endogenous antioxidant system is one approach to preventing or minimizing ROS-induced photoaging.5

With growing consumer appeal for natural and organic products, botanical extracts have become among the most commonly used ingredients in OTC antiaging cosmetic preparations. More recently, claims have focused on their antioxidant properties and ability to modulate certain types of environmental damage. Essential oils in particular, traditionally used for aromatic properties, have good penetration into the skin, which enhances their efficacy.6

In the present article, the authors evaluate the chemical composition and biological activities—i.e., antioxidative, antibacterial and antifungal—of wild Amazonian basil Ocimum micranthum Willd. (also known as O. campechianum Mill.) Labiatae essential oil, and compare these properties with those of commercially available common basil Ocimum basilicum and Thymus vulgaris essential oils.7 In addition, in view of their high antioxidant capacities, the oils were further assessed to determine if their functional capacity could be expressed in finished cosmetic products, and whether the type of formulation could influence the expression of their antioxidant activity.

Lab Practical: Using Essential Oils

  • It is important to check the safety information for each essential oil.
  • Essential oils are potent and small amounts of them go a long way.
  • Add an antioxidant to essential oil-containing formulations to keep peroxides at low levels; there is evidence that hydroperoxides formed from some components of essential oils can cause skin sensitivity.
  • Essential oils must be added at the end of the emulsification process (under 50°C)
  • Formulations with essential oils should be stored in a cool dry place, away from heat and light, to avoid degradation and rancidity.
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