Tuesday, January 17, 2012
Essential oils: Rosemary essential oil - anti-oxidant and anti-microbial?
Rosemary essential oil has been used as an anti-oxidant for quite some time - we can see this in the use of ROE or rosemary oleoresin extract (I think that's what that stands for - I've seen a few interpretations). There are countless studies on this topic, but I'll quote a few here. This one, from the awesomely named journal Meat Science, found that "The effect of the addition of rosemary essential oil on the oxidative stability of frankfurters depended on the level of added essential oil and the characteristic of the frankfurter. The rosemary essential oil successfully inhibited the development of lipid and protein oxidation in IF with that antioxidant effect being more intense at higher concentrations of essential oil." (Read the entire study to see the effects on white pigs, which weren't so great. IF stands for Iberian pigs.) This study concluded that "Strong inhibition of LP [lipid peroxidation] in both systems of induction was especially observed for the essential oil of rosemary." This study, entitled Antioxidant Activities of Rosemary, Sage, and Sumac Extracts and Their Combinations on Stability of Natural Peanut Oil, concluded that "Rosemary extract (except for 3 and 4 h) exhibited the most antioxidant effect compared with other individual extracts." In a study researching if rosemary and sage essential oils could retard rancidity on par with BHT. "Plant essential oils inhibited oxidative deterioration of liver pâtés to a higher extent than BHT did." (Estévez, M., Ramírez, R., Ventanas, S., & Cava, R. (2007). Sage and rosemary essential oils versus BHT for the inhibition of lipid oxidative reactions in liver pâté. LWT - Food Science & Technology, 40(1), 58-65.)
This study found that "rosemary extract had a higher antioxidant activity than blackseed essential oil", which really doesn't tell us much about anything, but I figured I should include all the studies I found instead of cherry picking those which confirmed my position.
this study noted: "In the present study, the antimicrobial activity of the essential oils from clove (Syzygium aromaticum (L.) Merr. et Perry) and rosemary (Rosmarinus officinalis L.) was tested alone and in combination...Both essential oils possessed significant antimicrobial effects against all microorganisms tested...The antimicrobial activity of combinations of the two essential oils indicated their additive, synergistic or antagonistic effects against individual microorganism tests." Very interesting!
This study - The Chemical composition, antimicrobial and antioxidative activity of laurel, sage, rosemary, oregano and coriander essential oils - concluded that "The oils showed a high degree of inhibition against all the microorganisms tested. The highest and broadest activity was shown by the oil of oregano, while the oil of sage was the least effective."
And take a look at this study relating to the P. acnes bacteria (the bacteria that causes acne). "Significant changes in morphology and size of P. ACNES were observed by atomic force microscopy (AFM) in response to essential oil treatment...In conclusion, the AFM investigation of morphology and size of P. ACNES treated with rosemary essential oil represents a powerful technique, which can generally be applied to reveal the biological changing mechanisms of bacteria induced by antibacterial agents at the nanometer level." (Yujie, F. (2007). Investigation of Antibacterial Activity of Rosemary Essential Oil against Propionibacterium acnes with Atomic Force Microscopy. Planta Medica, 73(12), 1275-1280.) Now I realize that this study was all about the coolness of the atomic force microscope and not about how rosemary essential oil might be used against acne, but it is interesting to see that when P. acnes encounters rosemary essential oil, it withers and dies, which I think could give us some proof that it is good for acne (although I've been going on the assumption that it's because of the oil fighting properties!).
This study noted, "...basil, rosemary, and sage essential oils did not show antifungal activity against Candida isolates at the tested concentrations." And this study summarized: "The essential oil of R. officinalis showed strong antimicrobial activity against: S. aureus, S. epidermis, P. aeruginosa, E. faecalis, K. pneumonia, and E. coli, moderate effect against S. bruneii, and no effect against C. albicans. It was previously mentioned that the essential oil of R. officinalis exhibit a significant antibacterial activity only against K. pneumoniae and P. aeruginosa, although its activity against C. albicans is lower compared to the essential oils of Thymus sp. and Calamintha sp."
So it looks like rosemary essential oil is pretty good with bacteria, but not so great with yeasts/fungi. How does it work with larger creatures?
Rosemary essential oil "has been shown to be an effective repellent (Hori, 1998; Koschier & Sedy, 2003), fumigant, and contact insecticide against a range of insect and mite species, with particular efficacy against stored product pests..." and it might be an effective because of the "1,8-cineole and α-pinene were determined to be the most toxic constituents to the two-spotted spider mite" (Click here for the entirety of this study.)
So I think it's safe to say that rosemary essential oil has demonstrated anti-oxidant properties. What about the anti-microbial properties? I think the science is showing that rosemary essential oil has anti-bacterial properties but isn't so great for anti-fungal properties.
Join me tomorrow as we take a look at the science behind applying it to our skin or using it as aromatherapy!