http://content.herbalgram.org/ogdenpress/HerbClip/review.asp?i=45267
 

Date: May 15, 2008                            HC# 090672-352

Re: Essential Oils Tested for Candida Infections: Mountain Savory, Lemongrass, and Cinnamon Bark are the Most Promising

Oberg K, Rolling L, Oberg C. Selection of essential oil components to inhibit Candida without affecting normal microbiota. The Journal of the Utah Academy of Sciences, Arts, and Letters. 2005;82:60-72.

Yeast (Candida albicans, C. glabrata) is normally found in the human gastrointestinal system and genitals in low numbers. Yeast strains compete with other members of the normal microbiota found in humans. When the immune system is weak or a metabolic imbalance occurs, yeast can reproduce more quickly, causing an infection known as candidiasis. Factors that can increase the risk of developing candidiasis include weakened immune systems, diabetes, medication use including broad-spectrum antibiotics and corticosteroids, and pregnancy. In addition, yeast infections can occur on the skin and mouth, such as "diaper rash" and thrush. Yeast can also enter the body through contamination of indwelling devices such as Foley catheters and feeding tubes. Drugs used to treat yeast infections have a limited effectiveness and are associated with adverse effects on normal microbiota, resulting in recurring yeast infections. Plants produce essential oils as defensive agents against microorganisms, and they are known to possess antimicrobial properties. The purpose of this study was "to determine which essential oils and individual oil components could be used as possible treatments for Candida infections without having an adverse effect on the normal human microbiota." The ideal candidate would be able to inhibit the growth of yeast species without inhibiting the growth of lactic acid bacteria (LAB), which represent normal vaginal bacteria.

The authors tested essential oils obtained from Young Living Essential Oils Inc. (Payson, Utah). The essential oils tested include tea tree (Melaleuca alternifolia) oil, spearmint (Mentha spicata) oil, rosewood (Aniba rosaeodora) oil, rose (Rosa spp.) oil, peppermint (Mentha x piperita) oil, palmarosa (Cymbopogon martinii) oil, nutmeg (Myristica fragrans) oil, mountain savory (Satureja montana) oil, lemongrass (Cymbopogon citratus) oil, lavender (Lavandula angustifolia) oil, geranium (Pelargonium spp.) oil, eucalyptus (Eucalyptus citriodoria) oil, coriander (Coriandrum sativum) oil, and cinnamon (Cinnamomum spp.) bark oil. The essential oils were tested against the yeast species C. albicans and C. glabrata using the disc assay. Individual constituents of the essential oils with the largest zones of inhibition were further tested against the two yeast species. Those constituents with the largest zones of inhibition were tested against LAB using the disc method.

The essential oils that demonstrated the largest zones of inhibition (>10 mm) against the two yeast species were mountain savory, lemongrass, and cinnamon bark oils. Essential oils with medium-sized zones of inhibition (3-10 mm) include spearmint, rosewood, palmarosa, and eucalyptus oils. The essential oils showing the smallest zones of inhibition (<3mm) were tea tree, lavender, nutmeg, and coriander oils. In general, C. glabrata was more sensitive to the essential oils than C. albicans. Out of 30 essential oil constituents tested, 25 demonstrated inhibition; however, most showed only small zones of inhibition. The essential oil constituents showing the largest zones of inhibition include citral, cinnamaldehyde, eugenol, perillaldehyde, terpineol, furaldehyde, and carvacrol. Citral, cinnamaldehyde, eugenol, geraniol, perillaldehyde, citronellol, and carvacrol demonstrated larger zones of inhibition against both yeast species than the commercial yeast infection treatments Nystatin cream, Vagisil, Miconazole 7, and Loprox gel. Essential oil constituents demonstrating medium zones of inhibition include geraniol, nerol, heptanol, and jasmone. Those demonstrating no zones of inhibition include heptadecane, myrcene, caryophyllene, farnesol, and humulene. Some of the essential oil constituents formed diffusion rings in the agar during the LAB disc tests, making it difficult to form conclusions from the data. However, all of the essential oil constituents performed favorably against the LAB strains, showing less growth inhibition than the commercial products. Only two of the essential oil constituents (cinnamaldehyde and citral) showed large zones of inhibition against all LAB strains.

This study shows that some essential oils and their constituents, notably citral cinnamaldehyde, eugenol, perillaldehyde, terpineol, furaldehyde, and carvacrol, are at least comparable, if not more effective than commercial yeast infection products in inhibiting the growth of yeast. In addition, the essential oil constituents produce less inhibition of LAB growth than the commercial products, indicating a less deleterious effect on normal human microbiota. It is important to point out that the authors compared pure essential oils and even pure isolated compounds from essential oils to commercial consumer products rather than to the isolated pure compounds in those products such as miconazole and nystatin. This is not "apples to apples" and the essential oils and isolates would certainly be expected to be more potent than creams and gels formulated for safe consumer use. This work points to the promise of developing effective products containing these essential oils for candidiasis treatments rather than using high concentrations of the oils themselves. These oils and isolates as tested in the lab would not be used at such concentrations due to the high likelihood of irritation and possible allergic reaction. Much lower concentrations would have to be utilized clinically as the author indicates.

Possible mechanisms of action for the observed antifungal effects of the essential oils and their constituents include inhibition of glucose uptake and changes in cell membrane permeability. When the mechanisms of action are better understood, it may be possible to select essential oil constituents with different mechanisms of action, thus reducing the development of resistant yeast strains. It is possible that essential oil constituent products could be developed for use against thrush, diaper rash, and vaginal yeast infections.

—Marissa N. Oppel, MS