Eugenol Basics
Eugenol is found in many essential oils and herbs. For example, it is found at a high potency in clove bud essential oil but also at a lower dose in cinnamon leaf and its essential oil. It is also found in pimento, bay, sassafras, massoy bark oils, oil of camphor and chamchwi plants according to PubChem. The potency and concentration varies widely depending on the source and extraction method. Further, this is not merely a powerful biofilm agent; it has other amazing properties such as anti-viral actions and anti-cancer effects.
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Indeed, oral and genital Herpes, HSV-1 and HSV-2, respectively, could not reproduce in the presence of eugenol. Al-Sharif has shown significant cancer effects. A very low concentration (2 μM) has specific toxicity against different breast cancer cells. This killing effect was mediated through inducing a cancer cell death path and decreasing the levels of E2F1 and survivin--two molecules that are essential to cell survival. It also hindered breast cancer genes.
Eugenol and Biofilms
Recently, Dr. Zhou has reminded us of a special process that is involved in the formation of dangerous biofilms. Basically, many bacteria have a “chatty” way of talking to other cells such as other bacteria. So, bacteria use chemicals or cause other bacteria to make chemicals to help them survive and often act to harm you or a loved one. Eugenol is so effective that at very low amounts, it still disrupted bacteria chemical communication. This is very important in a biofilm destroying agent. If cells cannot communicate, it is doubtful they can form communities. Biofilms are community creations. Further, eugenol at very low doses, called “sub-inhibitory concentrations” inhibited biofilm
Linalool
In terms of biofilms, it seems to be most effective when the essential oil part is used, which has the most evidence of killing Candida albicans. (Candida albicans is the cause of yeast infections.) Yet, again, it is the essential oil fraction that not only inhibits the growth of Candida albicans but also of the bacteria Lactobacillus casei, Staphylococcus aureus, Streptococcus sobrinus, Porphyromonas gingivalis and Streptococcus mutans cell suspensions, all of them associated with oral cavity disease, according to Alviano and Mendonça-Filho. Yet, Budzyńska reported this essential oil did not fully remove biofilms formed by Staphylococcus aureus (ATCC 29213) and Escherichia coli (NCTC 8196) on the surface of routine medical materials such as urinary catheters, infusion tubes and surgical mesh. Hsu found that linalool could be effective against Candida albicans due to its many genetic blocking effects. For example, using a scanning electron microscope and other technology, many signs of the effect of linalool to destroy Candida or inhibit its growth could be noted. Hsu found blocking actions against genes involving adhesion production and the formation of “branches” or the mold’s hyphae were both decreased by linalool.
Terpenoids
I would like to mention a class of options that come from a familiar substance, chemicals from tea tree oil. We have already mentioned linalool which is part of this class individually, since it comes up as a leading biofilm killer. According to Raut, as many as 14 terpenoids derived from tea tree oil inhibit biofilms, and α-terpineol, nerol, isopulegol, carvone, linalool, α-thujone and farnesol are worthy of special note. Eight terpenoids have effects on mature yeast biofilms (Candida albicans). A study by Ramage shows tea tree oil (TTO), terpinen-4-ol (T-4-ol), and α-terpineol displaying potent activity against 69 biofilm-forming Candida strains, of which T-4-ol and α-terpineol displayed rapid kill action. Of these three, T-4-ol displayed no significant toxicity to cells. These data provide further laboratory evidence that TTO and its derivative components, specifically T-4-ol, exhibit strong antimicrobial properties against fungal biofilms. Further, T-4-ol appears to possess safety advantages over the complete essential oil (TTO) and may be suitable for prevention and treatment of established oral and upper throat cavity candidosis. Certain terpenoids are components of spices or food ingredients generally regarded as safe (GRAS) (Pauli 2006).
Recently, various studies have reported the anti-Candida biofilm activities of several important terpenes (Dalleau et al. 2008; Khan & Ahmad 2012). In this study, the activities of 28 terpenoids were analysed, 18 of which were studied against biofilms of C. albicans for the first time. Diflucan (fluconazole) was used as a standard drug, and was completely ineffective against Candida biofilm development. This routine yeast had significant growth even at a high drug concentration: 250 times more than the MIC for planktonic growth (single yeast cell growth) (Raut). Addition of terpenoids to early-phase biofilms (i.e. immediately after adhesion) prevented biofilm development. Farnesol, isopulegol, thymol, carvone, nerol, carvacrol, eugenol, α-thujone and β-ionone were also potent inhibitors of biofilm development.
Allicin and Garlic
Garlic has been used as a medicine throughout human history. Allicin is considered one of the medically useful components of garlic.
Lihua reported ten years later that allicin impacts Pseudomonas aeruginosa biofilm. This is hardly casual information, since P. aeruginosa is likely resistant to multiple antibiotics, and this resistance may be due to biofilms. Organosulfur allicin has been shown to inhibit surface-adherence of bacteria and Lihua demonstrated that allicin could inhibit early bacterial adhesion which is a first step to bacterial community formation, usually just before biofilm production.
Candida grows in biofilms. The biofilms are a barrier to antifungal drugs. Allicin showed significant reduction in biofilm growth compared to fluconazole. Amazingly, allicin also altered Candida genetics to decrease biofilm formation