Ethnopharmacological relevance: Traditionally, garlic (Allium sativum L.; Alliaceae) has been known to boost the immune system. Aged garlic has more potent immunomodulatory effects than raw garlic. These effects have been attributed to the transformed organosulfur compounds; the identity of the immunomodulatory proteins in aged garlic extract (AGE) is not known.
Aim of the study: The major aims are to examine the changes occurring in the protein fraction during ageing of garlic and to identify the immunomodulatory proteins.
Materials and methods: Changes occurring in garlic during ageing have been examined by protein quantitation and gel electrophoresis. Purification and identification of the immunomodulatory proteins have been achieved by Q-Sepharose chromatography and mitogenic activity.
Results: Only two major proteins (12-14 kDa range by SDS-PAGE) are observed in AGE. The purified protein components QA-1, QA-2, and QA-3 display immunomodulatory and mannose-binding activity; QA-2 shows the highest mitogenic activity. The identity of QA-2 and QA-1 proteins with the garlic lectins ASA I and ASA II, respectively, has been confirmed by hemagglutination analysis. QA-3 exhibits mitogenic activity, but no hemagglutination activity.
Conclusions: The immunomodulatory activity of AGE is also contributed by immunomodulatory proteins. The major immunomodulatory proteins have been identified as the well-known garlic lectins.