Garlic Antiviral properties
In comparison with the antibacterial action of garlic, very little work has been done to investigate its antiviral properties.
But garlic (Allium sativum) has been shown to have antiviral activity, but the compounds responsible have not been identified. Using direct pre-infection incubation assays, we determined the in vitro virucidal effects of fresh garlic extract, its polar fraction, and the following garlic associated compounds: diallyl thiosulfinate (allicin), allyl methyl thiosulfinate, methyl allyl thiosulfinate, ajoene, alliin, deoxyalliin, diallyl disulfide, and diallyl trisulfide. Activity was determined against selected viruses including, herpes simplex virus type 1, herpes simplex virus type 2, parainfluenza virus type 3, vaccinia virus, vesicular stomatitis virus, and human rhinovirus type 2. The order for virucidal activity generally was: ajoene > allicin > allyl methyl thiosulfinate > methyl allyl thiosulfinate. Ajoene was found in oil-macerates of garlic but not in fresh garlic extracts. No activity was found for the garlic polar fraction, alliin, deoxyalliin, diallyl disulfide, or diallyl trisulfide.
Fresh garlic extract, in which thiosulfinates appeared to be the active components, was virucidal to each virus tested. The predominant thiosulfinate in fresh garlic extract was allicin. Lack of reduction in yields of infectious virus indicated undetectable levels of intracellular antiviral activity for either allicin or fresh garlic extract. Furthermore, concentrations that were virucidal were also toxic to HeLa and Vero cells. Virucidal assay results were not influenced by cytotoxicity since the compounds were diluted below toxic levels prior to assaying for infectious virus. These results indicate that virucidal activity and cytotoxicity may have depended upon the viral envelope and cell membrane, respectively. However, activity against non-enveloped virus may have been due to inhibition of viral adsorption or penetration.
The few studies have reported that garlic extract showed in vitro activity against influenza A and B (Fenwick and Hanley, 1985 ), cytomegalovirus (Meng et al., 1993 ; Nai-Lan et al., 1993), rhinovirus, HIV, herpes simplex virus 1 (Tsai et al., 1985 ), herpes simplex virus 2 (Weber et al., 1992 ), viral pneumonia, and rotavirus. Allicin, diallyl trisulfide and ajoene have all been shown to be active (Hughes et al., 1989 ; Weber., 1992 ).
In the case of HIV, it is thought that ajoene acts by inhibiting the integrin dependent processes (Tatarintsev et al., 1992 ). Allyl alcohol and diallyl disulfide have also proven effective against HIV-infected cells (Shoji et al., 1993 ). No activity has been observed with allicin or S-allyl cysteine. It appears that only allicin and allicin-derived substances are active. Taken together, the beneficial effects of garlic extract make it useful in medicine. There are insufficient clinical trials regarding the effects of garlic in preventing or treating the common cold. A single trial suggested that garlic may prevent occurrences of the common cold, but more studies are needed to validate this finding. This trial randomly assigned 146 participants to either a daily garlic supplement (with 180 mg of allicin content) or a placebo for 12 weeks.
The investigation revealed 24 occurrences of the common cold in the garlic group compared with 65 in the placebo group, resulting in fewer days of illness in the garlic group compared with the placebo group. However, claims of effectiveness of garlic on common cold appear to rely largely on poor quality evidence (Lissiman et al., 2012 ). Many countries have used garlic extract for clinical treatments, but the untoward actions of garlic following long-term administration should be fully noted. Even though many studies on garlic and its derivatives have been performed, the exact biological mechanism of garlic extract still remains to be elucidated.
Additionally the composition of various commercial garlic products. Including garlic powder tablets and capsules, oil-macerated garlic. Steam-distilled garlic oils, garlic aged in anqueos alcohol. And fermented garlic oil was determined as well ass the virucidal activated of the products against herpes simplex virus type 1. and parainfluenza virus type 3. virucidal activities of commercial products were de-pendent upon their preparation process. Those products producing the highest level of allicin and other thiosulfinates has the best virucidal activities.