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.(ABSTRACT TRUNCATED AT 250 WORDS)

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The antiviral and virucidal compound, hypericin, was studied regarding its activity and possible mechanism against herpes simplex virus (HSV-1). It was determined that hypericin caused slight inhibition of viral adsorption to and penetration of Vero cells. Additionally, yield reduction assays suggested that hypericin was most effective against HSV-1 as a virucidal agent rather than as an intracellular antiviral agent. Fluorescence microscopy revealed that hypericin initially associated with cytoplasmic membranes and that over the course of time it became concentrated in intracellular membranous regions, probably the Golgi apparatus or endoplasmic reticulum (ER). These concentration events failed to inhibit glycosylation of either viral or cellular proteins and were effectively blocked by compounds which inhibit endocytosis or membrane cycling between the ER and Golgi. Based on fluorescence studies, it was determined that hypericin had non-specific affinity for protein and higher affinity for detergent and lipid. The evidence suggested that strong, non-specific association with membranes, both viral and cellular, are probably the basis of hypericin's virucidal and antiviral activity.

These extracts had direct virucidal activity as well as intracellular antiviral activity against both DNA and RNA viruses. Antiviral activity was achieved with extract concentrations significantly lower than those necessary to produce cytotoxic effects. Additionally, extracts were less toxic to normal cells than to the tumour cells tested.

to which 1 ml of a serially diluted plant extract was added to give a final cell concentration of I 0 cellIml. The test tubes were incubated at 37°C (30°C for C. albicans) overnight and examined spectrophotometrically. The concentration which showed no turbidity was taken as the MIC. Aliquots of 1 ml of the test tubes showing no sign of growth were placed onto petri dishes containing nutrient agar in triplicate. After an overnight incubation period the plates were examined for the presence of colonies. The concentration that gave no visible colonies was taken as MBC. The MIC experiments were repeated three times. The results obtained showed that the methanol fraction exhibited significant activity against the three test microorganisms whereas the aqueous, the petroleum ether, and the dichloromethane fractions had no activity against the organisms (Table 1).