Ancient Essential Oils: Exploring the Effects of Age on Bioactivity

Abstract

It seems reasonable to expect that the molecular composition and bioactivity of essential oils will undergo changes after protracted storage times, reflecting, among other things, the effects of differential evaporation, photo-oxidisation or temperature. These effects may produce significant changes despite careful handling and storage during the ensuing storage period. Long-term effects are not expected to be consistent across a range of oils, which makes it relatively difficult to predict successful preservation or changes in activity as benign or otherwise. Here we compare the composition and bioactivity of oils prepared by hydrodistillation from a range of common aromatic plants over 75 years ago and subsequently stored at room temperature with oils from the same species recently hydrodistilled in our laboratory or sourced from commercial suppliers. Tests for bioactivity focus on free radical scavenging, antioxidant, antimicrobial and antifungal activities across a range of essential oils; using DPPH, FRAP, broth dilution/disc diffusion and a core transplant method, respectively. TLC and TLC-bioautography is used to further correlate effects of likely changes in chemical composition with bioactivity of discrete components identified following characterization using GC/MS. Results may serve as a useful guide for appropriate preservation of commercial essential oils.