Spice Up Your Life!
The Antimicrobial Effects of Spices
Emma Marsh and Sarah Paumier
Introduction
With the development of ever increasing numbers of antibiotic-resistant bacterial strains, it has become very important to find alternative methods of treating bacterial infections. Many everyday compounds are being examined for biological activity as a result, and some recent studies on spices have promising results. Several studies have been conducted to determine the ability of spices to inhibit pathogenic bacteria growth. Garlic, oregano, and cloves have displayed a strong ability to combat pathogenic bacteria, in some cases proving even more effective than the antibiotics currently in use, especially for strains of bacteria known to be antibiotic-resistant (Arora and Kaur, 1999). Several other spices show lesser degrees of bacteria inhibition, including peppers, onion, thyme, and lemon juice. This page gives a brief overview of lab-based experiments performed with garlic and basil, two well studied spices.
Use of these spices in cooking tends to be higher in areas of warmer climate, including Mexico, the Middle East, and India. Historically, before modern preservation methods, a warmer climate would cause food to spoil faster, and the use of these spices may very well have aided food preservation by inhibiting bacterial growth. It is also interesting to note that these antimicrobial spices tend to be used more often in meat dishes than in vegetable ones. This is likely due to the presence of a cell wall in plants, which provides the vegetables with added protection against bacterial infection, while the absence of a cell wall in animals makes the meat cells more vulnerable (Sherman and Hash, 2001).
With bacteria rapidly acquiring resistance to the most commonly used antibiotics, and human immune systems developing allergic reactions to many of these, it is becoming increasingly urgent that new, effective methods of treating infections be found (Singh et al, 2002). Spices, which are already used in daily life, are safe, effective treatments that can easily be researched for future drug development. In addition, spices are found easily throughout the world, including poorer and less developed regions that may not have access to modern antibiotics. If effective herbal treatments can be developed, antibacterial health aids will become more universally available. Rather than dealing with unregulated herbal supplements, which may produce unknown side effects, antibiotic spices oftentimes need only be boiled to form an extract in order to create an effective treatment, and since these compounds are used regularly in food, dangerous side effects would be rare (O'Mahony et al, 2005). In addition, some promising new research has been done that involves replacing antibiotic growth supplements with less harmful spices, which it outlined here in both swine and poultry.
How to test bacterial growth inhibition:
Many spices have been tested for their degree of antimicrobial properties the same way as antibiotics being tested for formal medicinal purposes, namely through disc diffusion assay. This technique involves growing bacteria on agar in the presence of filter-paper discs that have been soaked in the substance under investigation. If the bacteria fails to grow, the presence of antimicrobial agents is evident. The MIC, or minimum inhibitory concentration is also crucial to determine when using a compound for any sort of medicinal purpose to see how high a concentration is needed for a given substance to be effective in blocking bacteria growth. This is usually determined by placing varying concentrations of the possible antibacterial in a test tube with an infected growth medium. The lowest concentration that shows no signs of microbial growth, in this case, turbidity is deemed the MIC (Maidment et al, 2006).
The Secret of Essential Oils
Spices such as cloves and cinnamon have been used for hundreds of years to fight bacteria infections, parasites, and even rid a person of persistent flatulence (Knobloch et al, 1989). Essential oils can be extracted from plant remnants in varying percentages through the process of steam distillation. Cloves by weight contain roughly 15% oil product, while cinnamon bark leaves only 1-2% after distillation, making some oils more scare than others. These essential oils in turn also have antimicrobial properties, which may be even more potent than dry versions of the same spices. One of the main bacteria fighting components of these two spices is thought to be eugenol, which makes up 73-85% of the clove oil. There is also 10% eugenol in cinnamon extract, with an additional 50-80% cinnamaldehyde. One current theory for how essential oils of various spices show antimicrobial affects is through their ability to penetrate bacterial and fungal cell walls. Therefore, an oil’s affects should correspond with how soluble these oils are in the phospholipids bilayer of cell membranes (Knobloch et al, 1989).
From the research of Maidment and his collegues testing these two spices against Staphylococcus albus, Escherichia coli B and Saccharomyces cerevisiae bacteria, it seems that the essential oils are more effective when used in an alcohol extract instead of a water based extract since the antimicrobial components (the eugenol and cinnamaldehyde) are more soluble in ethanol than water. However, the journal article does not mention if the antimicrobial effects of these alcohol based extracts were at all influenced by the antimicrobial effects of the ethanol itself rather than the spices alone. In order to control for the ethanol effect, it would have made more sense for the researchers to include pure ethanol as a control to compare any resulting bacterial inhibition with that of the spice extracts. These particular bacteria were chosen to give an example of three different types of cell walls. The testing consisted of the standard disk diffusion assay and utilized both whole cloves and powdered cinnamon as well as the essential oils of each. First the cloves were ground, and then were mixed in a suspension of 1 part powdered spice to 7 parts ethanol. The same 1:7 ratio was also used in the water extract condition for powdered spices, and for the oil in ethanol condition. The researchers also performed and MIC test. The alcoholic powdered cinnamon was found to have a lower MIC than the cloves at 3.9 x 10^-3 micrograms against all tested organisms, while cloves showed the MIC only against E. coli (Maidment et al, 2006).
Choice Spices
Garlic
Garlic is one of the most active antimicrobial spices. It has activity against both Gram positive and Gram negative bacteria, including many strains that have become resistant to antibiotics such as penicillin (Banerjee and Sarkar, 2003). There are several proposed mechanisms of action for garlic, depending upon the nature of the microbe. For fungi of the genus Candida, it is thought that garlic oxidizes L-cysteine glutathione-2-mercaptoethanol, which is part of several essential proteins, thereby causing enzyme inactivation and inhibition of cell growth (Arora and Kaur, 1999). Candida albicans, which causes superficial infections in the skin and mucous membranes, is effectively inhibited by garlic extract, indicating that this treatment may be useful as a topical medicine to treat an infection of this fungi (Arora and Kaur, 1999). In tissue of the digestive tract, it is believed that garlic induces cell apoptosis, both of the gut cells and of the bacteria present. Garlic decreases the membrane potential of the mitochondria in the gut cells, and of the bacterial cell membrane, as a result increasing caspase-3 activity, which leads to a greater rate of cell death. This effect on the gut cells is what creates garlic's anticancer properties, while the effect on the bacteria is the source of its antimicrobial properties in the gut (Su et al, 2006). Several families of bacteria are affected by the antimicrobial activities of garlic, including several members of the genus Shigella, but the exact mechanisms have not yet been uncovered. Evidence of the potency of garlic, however, not only explains the current usage of this spice as medication, but indicates that it should be more widely used in the future. The effectiveness of garlic against Shigella, for example, supports the usage of garlic extract as a treatment for bacillary dysentary, which is caused by Shigella dysenterieae. Garlic extracts only retain their antimicrobial effects for so long, however. Storage for several days at 4 degrees Celsius decreased antimicrobial function, and heating of the extract completely destroyed the inhibitory component. Incubation at 37 degrees Celsius will retain the antibacterial effect for a few days, yielding the best results. Overall, garlic extracts are most effective when freshly produced (Arora and Kaur, 1999).
Basil
The common basil plant belongs to one of many subspecies of O. basilicum L. When studying this popular spice, there has been considerable contradiction within the available research because there are so many different varieties of this plant, and chemical composition has been shown to vary widely between localities based on climate. Surrounding plants also have an affect on the chemical composition due to interspecific hybridization, which leads to polymorphism (Paton and Putievsky, 1996). Most commonly, these different Basil chemotypes contain varying amounts of allyl-phenol derivatives, including methyl chavicol (estragole), eugenol, and methyl eugenol along with the monoterpene alcohol, linalool. Despite this generalization, the variation is still daunting. In Thailand, a basil study discovered there to be 100 different compounds present, and in the Phillipines, more than 130 were found. (Suppakul et al, 2003).
In fact the distinctions between basil subspecies is so specific that it may even come down to chirality, making it useful to consider the enantiometeric composition during identification. In the work of Ravid and his colleagues (1997), using the native basil species in Thailand: Ocimum sanctum L., Ocimum gratissimum L., and Ocimum canum Sims, as well as several commercial basil subspecies, key enantiometic differences were found within the chemical linalol between subspecies. While the linool from O. basilicum L. and the commercially used basil oils, consisted of optically pure (R)-(-)-linalool, whereas O. sanctum L. and O. canum Sims contained (S)-(+).
Click here for a link to the chemical structures of some of the components of basil!
http://pubs.acs.org/isubscribe/journals/jafcau/51/i11/figures/jf021038tf00001.html
Animal Studies
Growing concern about the use of antibiotics in livestock feed, and the recent prohibition of such practices throughout much of Europe, has created an opening for trials regarding the use of antimicrobial spices in a similar role (Turner et al, 2001). The currently used compounds are intended to enhance growth and prevent disease in livestock, but have also lead to the creation of many antibiotic-resistant strains of bacteria. Recent studies of natural compounds hope to uncover a substance that provides the same benefit to the animals as antibiotics without the dangerous side effects for the rest of the world (Turner et al, 2001). Despite the high level of interest of the feed industry and animal breeders in such studies, it is very difficult to find the resources necessary to conduct such an experiment (Kamel, 2001). Private companies lack the manpower and financial resources to support long-term research programs and public institutions have difficulty finding the governmental support to fund such a project. Several institutions have come together over this common goal, however, and a few studies have begun. Food suppliers are being held responsible for all additives, and must present evidence regarding the composition, technical and zootechnical efficacy, toxicity analysis, feed traceability, residue analysis, and exposure and handling risks of all products used in these new experimental feeds (Kamel, 2001).
Swine
One study, conducted on a commercial farm in Switzerland, added a precise combination of plant extracts to the diets of early-weaned pigs to determine the effects on weight gain (Kamel, 2001). Results indicated these extracts, especially when coupled with organic acids, benefited the piglets and helped counter the stress associated with early weaning. Further studies are being conducted to determine exactly what mechanisms are affected and how the benefits are derived, to further specify the dietary additive that provides the most benefit without causing harm (Kamel, 2001).
A second study integrated spices that have been shown to possess antimicrobial activity in vitro, such as thyme, cinnamon, garlic, oregano, and sage, to examine their in vivo potential (Turner et al, 2001). These compounds were fed to pigs in order to observe the effects on their growth and overall health. Garlic produced mixed results: it was found to decrease weight gain and feed intake and efficiency in weanling pigs, but, along with cinnamon, showed decreased mortality in nursery pigs. The amount added seemed to have a large effect on the results as well. When cloves were added so that they constituted 0.5% of the diet, the pigs exhibited maximum growth. When the amount was raised to 2.0% of the diet, weight gain and feed intake was decreased below the level shown by the control diet. None of the other spices tested have shown significant benefits to the pigs, and quite a few have shown to be much less beneficial than the current medicated diet. Further research is necessary to discover how to translate the antimicrobial properties and benefits in vitro into equivalent benefits in vivo (Turner et al, 2001).
Poultry
There has also been similar investigation into natural growth promoting substances, which would possibly replace antibiotics present in poultry feed (Ciftci et al, 2005). Anise is a plant native to many warm regions including Iran, India and Turkey. It’s active ingredient is anothole, which makes up 85% of the herb, but anise also contains eugenol, methylchavicol, anisaldehyde and estragole. Of these key components, which together produce antibacterial, antifungal and antiparasitic effects, eugonol and anothole have also been found to have digestive stimulating effects, which is important in trying to increase the size of an animal. To test the effects of anise oil on animal diets, a study by Ciftci et al. (2005) utilized a total of 200 broiler chickens*, which were divided into five treatment groups. Three anise oil conditions were tested in which one group received feed with 100mg/kg anise oil, another 200mg/kg, and the last group 400mg/kg. The comparison antibiotic group used 10/kg Avilamycin, which amounts to a 0.1% antibiotic. A control group received neither anise oil nor antibiotic. To prepare the antibiotic researchers had to use hydro distillation to purify the essential oil, and then mix it with vegetable oil so it could be easily added to the animal feed, which consisted of 27% crude protein and 3.0-3.25 MCal ME/kg (Ciftci et al, 2005).
While there was no significant difference in chicken size during the first four weeks of treatment, week 5 showed promising results. The 400mg/kg anise oil group weighed the most at 70.35 g, which beat out even the antibiotic group whose average weight was only 65.84 g. The other anise groups and control groups weighed even less. The improved weight gain for the 400mg/kg anise oil group was very successful, showing a 15% gain over the control and 7% over the antibiotic group. While more studies will need to test these results before being implemented on an institutional wide scale, these results are truly hopeful (Ciftci et al, 2005).
*Broiler chickens are chickens that are produced for meat. For some examples, follow this link: http://images.google.com/images?client=safari&rls=en&q=broiler%2C%20bird&ie=UTF-8&oe=UTF- 8&um=1&sa=N&tab=wi
Conclusion
While there have been many culture-based laboratory studies into the antimicrobial effects of every day spices, as of yet, there have not been any studies that target these antiviral and antibacterial properties in humans. However, on a slightly different note, there is much excitement and growing research surrounding spices possible preventive properties against many debilitating diseases and conditions such as diabetes, cancer, and arthritis. While our findings on the research into animal feed were unexpected, spices certainly have the potential to eliminate the undue use of antibiotics as growth hormones, and possibly do much more.
References
Arora, DS and Kaur J. Antimicrobial activity of spices. International Journal of Antimicrobial Agents. 1999. 12(3): 257-262.
Banerjee, M and Sarkar, P.K. Inhibitory effects of garlic on bacterial pathogens from spices. World Journal of Microbiology and Biotechnology. 2003. 19(6): 565-569.
Ciftci M, Güler T, Dalkiliç B, Ertas ON. The Effect of Anise Oil (Pimpinella anisum L.) On Broiler Performance. International Journal of Poultry Science. 2005. 4 (11): 851-855.
Kamel, C. Natural Plant Extracts: Classical remedies bring modern animal production solutions. Cahiers Options Méditerranéennes. 2001. 54(3): 31-38.
Knobloch K, Pauli A, Iberl B, Weigand H, and Weis N. Antibacterial and antifungal properties of essential oil components. J. Essent. Oil Res. 1989, 1: 118-119.
Maidment C, Dyson A, and Haysom I. A Study into the Antimicrobial Effects of Cloves (Syzgium Aromaticum) and Cinnamon (Cinnamomum Zeylanicum) using Disc-Diffusion Assay. Nutrition and Food Science. 2006. 36(40): 225-230.
O'Mahony, R. et al. Bacteriacidal and anti-adhesive properties of culinary and medicinal plants against Helicobacter pylori. World Journal of Gastroenterology. 2005. 11(47): 7499-7507.
Paton A, Putievsky E, Taxonomic problems and cytotaxonomic relationships between and within varieties of Ocimum basilicum and related species (Labiatae). Kew Bull. 1996, 51, 509-524.
Prasad G, Kumar A, Singh AK, Bhattacharya A.K, Singh K, and Sharma VD. Antimicrobial activity of essential oils of some Ocimum species and clove oil. Fitoterapia. 1986. 57: 429-432.
Ravid U, Putievsky E, Katzir I, Lewinsohn E. Enantionmeric composition of linalol in the essential oils of Ocimum species and in commercial basil oils. Flavour and Fragrance Journal. 1997. 12(4): 293-296.
Sherman PW and Hash GA. Why Vegetable Recipes are Not very Spicy. Evolution and Human Behavior. 2001. 22(3): 147-163.
Singh, G. et al. Studies on Essential Oils: Part 10; Antibacterial Activity of Volatile Oils of Some Spices. Phytotherapy Research. 2002. 16: 680-682.
Su, C.C. et al. Crude extract of garlic-induced caspase-3 gene expression leading to apoptosis in human colon cancer cells. In Vivo. 2006. 20(1): 85-90.
Suppakul P, Miltz J, Sonneveld K, and Bigge SW. Antimicrobial Properties of Basil and Its Possible Application in Food Packaging. Journal of Agricultural Food Chemistry. 2003. 51(11): 3197 -3207.
Turner, L.J., Dritz, S.S., and Minton, J.E. Alternatives to conventional antimicrobials in swine diets. Professional Animal Scientist. 2001.
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Comments (17)
Dylan Hershkowitz said
at 7:25 pm on Feb 24, 2008
I know that it isn't used in food, but do you guys know how tea tree oil works in inhibiting bacterial and fungal growth?
Nick Katz said
at 9:56 pm on Feb 24, 2008
Who first thought to investigate the anti-bacterial properties of food spices, and why?
Elizabeth Heller said
at 7:16 pm on Feb 26, 2008
Very cool! How do the antimicrobial substances in these spices (such as eugenol) kill bacteria? Might some of them affect the structure of the bacteria in some way, or is it something else entirely?
Anonymous said
at 9:31 pm on Feb 27, 2008
Do they know whether the spices work by killing the bacteria, or by inhibiting their growth? (This is Emily Berger - I can't get my name to show up right now for some reason).
Peter Satin said
at 9:35 pm on Feb 27, 2008
are the molecules that grant these spices antibacterial properties being actively pursued by pharmaceutical comapanies in commercial drugs?
Edem Binka said
at 12:39 am on Feb 28, 2008
Since there are bacteria that have resistant strains to antibiotics, is it possible for bacteria to develop resistant to whatever is contained in those spices that kill them? If so, is there an amount of these spices that should be used to ensure that the bacterial species under investigation are completely killed off and none survive?
Adriana said
at 12:46 am on Feb 28, 2008
This is a really interesting topic! This is probably not the direction that you guys are headed, but in reading your intro, I was oddly reminded of the movie "Medicine Man". I don't know if anyone else has seen it (and sorry if you're confused as to why I'm bringing it up), but are there any other spices/herbs (only present in the warmer climates that you mentioned) which are facing extinction?
Katrina Mateo said
at 1:27 am on Mar 1, 2008
I did a similar research project in high school looking at the antimicrobial effects of cuisine spices on two types of bacteria - i found garlic to be most effective (concurring with the practice of using garlic to preserve foods) ... do garlics also contain a similar essential oil that gives it its antimicrobial characteristic?
Anonymous said
at 10:05 pm on Apr 1, 2008
I think a discussion about herbal medicine's validity in different cultures vs modern medicine would be really interesting especially considering how the use of antibiotics in soap and a drug and a generally sterile environment seems to be weakening immune systems!
Anonymous said
at 2:29 pm on Apr 21, 2008
the secret to essential oils: when comparing alcohol vs water extracts, wouldn't the alcohol extract normally have antimicrobial actions as it is alcohol?
Nick said
at 8:43 pm on Apr 21, 2008
In the article it says the effect of garlic is greatest when it is fresh. Would the bottles of garlic or garlic powder used in cooking (ie, not fresh) have reduced antimicrobial properties or none at all. How does freshness influence antimicrobial properties?
Anonymous said
at 8:47 pm on Apr 21, 2008
this is totally random but my mother used to make me take entire pills of oregano to prevent infection when I got a sun burn. (they were little plastic pills filled with literally oregano, and since I couldn't swallow big pills I had to just eat the oregano. yea, yuck!) But I was wondering what the antimicrobial mechanism for oregano might be, if there is any? (I really hope I didn't go through all that for nothing) - Kenia Rodriguez
Peter Satin said
at 12:01 am on Apr 22, 2008
can you elaborate on 'essential oils'? is it the same chemical distributed among many different species, or does each species have its own essential oil? if it is the same, what makes it an antimicrobial. if there exist many different kinds, is there any similarities between them that might clue into the active mechanism? also, how effective are these essential oils versus commercial drugs?
Anonymous said
at 3:47 pm on Apr 22, 2008
Shirley: Can't cinnamon treat some type of condition? But doesn't it also have side effects?
Dylan Hershkowitz said
at 9:38 pm on Apr 22, 2008
Is there an evolutionary connection between people finding these spices to be tasty and the spices having antimicrobial activity?
Katrina said
at 10:57 pm on Apr 22, 2008
I know that garlic supplements are relatively popular but are taken like vitamins - they're not used to fight a disease but are taken as a health supplement. Do these types of pills contain essential proteins that are found in fresh garlic? And if they're not used to inhibit bacteria growth, what is their purpose as a supplement?
Stephen Evans said
at 10:01 am on May 21, 2008
For something like Garlic, that has a long history of having purported medicinal benefits (the Roman physician Galen called Garlic the 'cure-all'); it's fascinating to apply modern-day analytic techniques to tease out some of the true (and bogus) scientific claims of such a compound as Garlic. Plants must deal with bacterial and fungal infections too, and delving into alternative sources for antibacterial and antifungal sources seems like a very promising venture.
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