REHOVOT, Israel , October 14, 1997 -- Garlic is believed to work wonders, fromfighting disease to keeping away vampires. Now two studies conducted at theWeizmann Institute of Science have uncovered a molecular mechanism which maybe the basis for some of garlic's therapeutic effects.
The researchers were able to study how garlic works at the molecular levelthanks to their unique biotechnological procedure for producing large quantities of pureallicin, garlic's main biologically active component.
One study, appearing in the October issue of the American Society forMicrobiology's Antimicrobial Agents and Chemotherapy, explains how allicin fights infection.This research supports the notion that garlic is an excellent, although smelly,natural antimicrobial drug that can disable an unusually wide variety of infectiousorganisms.
The second study, soon to be reported in Biochimica Biophysica Acta, may helpclarify the role allicin plays in preventing heart disease and other disorders.
In the studies, the scientists revealed and characterized a molecularmechanism by which allicin blocks certain groups of enzymes. Allicin, created when garlic cloves are crushed, protects the plant from soil parasites and fungi and is also responsible for garlic's pungent smell.
The studies were led by Profs. David Mirelman and Meir Wilchek of theWeizmann Institute's Biological Chemistry Department, who worked together withdepartmental colleagues Drs. Serge Ankri, Talia Miron and Aharon Rabinkov and with Prof. LevWeiner and Dr. Leonid Konstantinovski of the Organic Chemistry Department.
A natural weapon against infection, the research reported in October's Antimicrobial Agents and Chemotherapyrevealed that allicin disables dysentery-causing amoebas by blocking two groups ofenzymes, cysteine proteinases and alcohol dehydrogenases.
Cysteine proteinase enzymes are among the main culprits in infection,providing infectious organisms with the means to damage and invade tissues.Alcohol dehydrogenase enzymes play a major role in these harmful organisms'metabolism and survival.
Because these groups of enzymes are found in a wide variety of infectiousorganisms such as bacteria, fungi and viruses, this research provides a scientific basis forthe notion that allicin is a broad-spectrum antimicrobial drug, capable of warding off different types of infections.
"It has long been argued that garlic can fight a wide range of infections, andnow we have provided biochemical evidence for this claim," says Prof. Mirelman.
The role of allicin in warding off infection may be particularly valuable inlight of the growing bacterial resistance to antibiotics. It is unlikely that bacteria woulddevelop resistance to allicin because this would require modifying the very enzymes thatmake their activity possible.
Blocking mechanism explained in the study slated to appear in Biochimica Biophysica Acta, Institutescientists found that allicin blocks the enzymes by reacting with one of their important componentsknown as sulfhydryl (SH) groups, or thiols.
This finding has important implications because sulfhydryl groups arealso crucial components of some enzymes that participate in the synthesis of cholesterol. Byreacting with and modifying the sulfhydryl groups in those enzymes, allicin mayprevent the production of arteryclogging cholesterol.
"It has been suggested that garlic lowers the levels of harmfulcholesterol, and our study provides a possible explanation for how this may occur," saysProf. Wilchek. "However, more research is necessary to establish what role allicinmight play in preventing the clogging up of arteries."
Complicating the issue is the concern that blocking sulfhydryl groupsin proteins may sometimes be harmful because these groups are also present inenzymes involved in some of the body's vital processes. However, unlike most bacteria,human tissue cells contain detoxifying molecules of a substance called glutathione,which helps maintain appropriate sulfhydryl levels. These glutathione molecules canreverse the anti-sulfhydryl effects of small amounts of allicin.
Measuring antioxidant activity while reaction with sulfhydryl groups appears to explain most of allicin'sactivity, it has also been suggested that allicin acts as an antioxidant. The study reported inBBA confirmed this antioxidant effect and for the first time provided its quantitative assessment.
Antioxidants gobble up harmful free radicals believed to contribute to tumor growth,atherosclerosis, aging and other processes. Producing pure allicin in large quantitiesin nature, allicin is created when garlic cloves are cut into or crushed. Thecutting or crushing causes two components of garlic, alliin and the enzyme alliinase, tointeract.
The allicin produced at the Weizmann Institute is semi-synthetic; first,its precursor, alliin, is chemically synthesized, then a modified form of thenatural enzyme, alliinase, converts it into pure allicin.
The pure semi-synthetic allicin can be stored for months without losingits effectiveness. In contrast, the natural compound loses its beneficial propertieswithin hours because it begins to react with garlic's other components as soon as theclove is crushed.
A patent application for this production of pure allicin has been submitted byYeda Research and Development Co., the Weizmann Institute's technology transfer arm,and several companies have already expressed interest in scaling up the process forcommercial use and clinical testing.
Prof. Mirelman, the Weizmann Institute's Vice President for TechnologyTransfer, holds the Besen-Brender Chair of Microbiology and Parasitology, andProf. Wilchek, Dean of the Biochemistry Faculty, holds the Marc R. GutwirthChair of Molecular Biology.
Partial funding for this research was provided by the Center forMolecular Biology of Tropical Diseases at the Weizmann Institute and the Avicenne Programof the European Union. Drs. Rabinkov and Konstantinovski were partly supported bythe Center for the Absorption of Scientists of Israel's Ministry of Absorption.
The Weizmann Institute of Science, in Rehovot, Israel, is one of theworld's foremost centers of scientific research and graduate study. Its 2,400 scientists,students, technicians, and engineers pursue basic research in the quest for knowledge andthe enhancement of the human condition. New ways of fighting disease and hunger,protecting the environment, and harnessing alternative sources of energy are highpriorities.
Materials provided by Weizmann Institute. Note: Content may be edited for style and length.
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