OVER THE GROCERY COUNTER ANTIBIOTIC – WILL ALLICIN REPLACE
SOME COMMON ANTIBIOTICS?
In a recent laboratory exercise, I had my students test the antimicrobial activity of some conventional antibiotics and disinfectants. Out of a sudden surge of curiosity, I decided to have them test the relative efficacy of the much acclaimed garlic against selected organisms. Just before the lab started, I purchased some bulbs of garlic from the local grocery store for this purpose. I blended five average-sized cloves in about 100ml of de-ionized water, filtered the homogenate and presented the slightly turbid but debris-free solution to the students as an “unknown”.
I had the students follow the instructions below, based on the lab manual1, being a modified Kirby-Bauer method:
-Insert sterile absorbent paper discs into each solution
-Drain off excess fluid between paper towels
-Place discs on plates of Mueller-Hinton agar, seeded with bacteria.
-Label accordingly and incubate at 37oC until the next lab period
(about 48 hours)
The results were wide, clear zones of inhibition against Staphylococcus aureus and Escherichia coli by the garlic extract. The photograph below shows a sample result from one of the groups of students. (Filter paper disc on two sides of the plate were impregnated with the raw garlic extract)
Garlic Allium sativum, has been used as a medicinal herb for centuries.2 According to Sivam3, Louis Pasteur was the first to report the antibacterial effect of onion and garlic juices. Other activities include anti tumor4, reducing cholesterol5, and a wide spectrum of antifungal, antibacterial, antiviral and antiparasitic activities6. The main active ingredient in garlic is well known to be allicin. In addition to allicin, other components of garlic more stable than allicin, for example ajoen, have been found to have a variety of therapeutic applications2.
Since garlic is widely eaten, it could be regarded as safe. Eating large amounts of garlic has been associated with stomach irritation in some individuals, the ingestion of vitamin B1, olive oil or butter at the same time can minimize this7. Allicin itself, though not present in garlic intact garlic bulbs, is produced by the action of alliinase on alliin, both present in garlic, when the clove is crushed3.
Being such a wide spectrum antimicrobial agent, one might fear that garlic would harm beneficial gut bacteria. Again, garlic scores a pass mark here. This is because it has been found to kill most beneficial gut bacteria, whilst sparing most of the beneficial ones7 Allicin acts against the thiol (S-H) groups found in the enzymes of lower organisms. These enzymes are important in these organisms for building up important cell components, such as DNA , RNA and cell membrane, thus disallowing cell replication8. Because of this mode of action, no susceptible bacterial species has been found to develop any resistance to garlic3.
It is difficult to ignore the significance of the potency of this natural food product against such a wide range of microorganisms, especially in face of existing widespread resistance to many antibiotics. Another factor which may contribute to make garlic constituents more popular is the relatively low cost of raw garlic. However, there is the need to work on stabilize allicin for longer periods of time in order to maintain its antimicrobial activities.
Expectedly, garlic has generated much interest among microbiologists, and a lot is being done to maximize its applications. It is possible, in the near future to have it occupying an important position among conventional remedies for the treatment of diseases, especially those caused by microorganisms. It has been successfully used, on experimental basis, to work in synergy with some existing antibiotics9. The fascination with this herbal antimicrobial agent is likely to continue for a long time. It is quite conceivable that it could soon replace or complement some prescription antibiotic in common use now.
References
1. Kleyn J., Bicknell, M.2004. Microbiology Experiments - A Health Science Perspective. 4th Ed. Pp
109-117. McGraw Hill.
2. Mayeux PR, Agrawal KC, Tou JS, King BT, Lippton HL, Hyman AL, Kadowitz PJ Mc Namara DB 1988. The Pharmacological effects of allicin, a constituent of garlic oil. Agents and actions 25:182-90
3. Sivam PG. 2001.Protection against Helicobacter pylori and other bacterial infections by garlic. Journal of Nutrition 131:1106S-1108S
4. Siegers, C P, Steffern B, Robke, A. Pentz R. 1999. The effects of garlic preparations against human tumor cell proliferation. Phytomedicine. 6 (1): 7-11
5. Gebhardt R, Beck H, Wagner KG. 1994. Inhibition of Cholesterol biosynthesis by allicin and ajoene in rat hepatocytes and HepG2 cells. Biochim Biophys Acta 1213(1):57-62
6. Harris JC, Cottrell SL, Lloyd D. 2001. Antimicrobial properties of Allium sativum. Applied Microbiology and Biotechnology. 57(3):282-6.
7. Dharmananda S. 1996. Garlic Compounds
http://www.gaiaresearch.co.za/garlic.html
culled
8. Rabinkov A, Miron T, Konstantinovski, L, Wilchek M, Mirelman, D, Weiner L 1998. The mode of action of allicin:trapping of radicals and interaction with thiol-containing proteins. Biochim Biophys Acta 1379(2):233-244.
9. Jonkers D, van den Broek E, van Dooren I, Thijs C, Dorant E, Hageman G, Stobberingh E 1999. Antibacterial effect of garlic and omeprazole on Helicobacter pylori. Journal of Antimicrobial Chemotherapy 43(6):837-839
Toye Ekunsanmi
Assistant Professor - Biology
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