Immunostimulatory properties of fructans derived from raw garlic (Allium sativum L.)

- Raw garlic fructans (RGF) isolated in a yield of 13.8% on a fresh weight basis.
- NMR analyses indicated that RGF has (2→1) β-D-fructofuranosyl bonds.
- RGF display mitogenic activity towards murine splenocytes 4-5-fold increase).
- RGF promotes significant activation of macrophages (NO release and phagocytosis).
- RGF has the potential for use as a value-added food component for immunomodulation.

Garlic (Allium sativum L.), commonly used as a spice and traditional medicine has innumerable biological activities including immunomodulation. Fructans are present in abundance (14-17%, fresh wt.) in garlic. Although fructans from aged garlic extract have been shown to exert immunomodulatory properties, such information is lacking for fructans from raw garlic. The main objective of this study is to isolate raw garlic fructans (RGF) and investigate its effects on the cells of the immune system in vitro. RGF (detected by cold anthrone assay) was isolated, in a yield of 13.8 g/100 g (fresh weight) garlic, from the flow-through pool of Q-Sepharose chromatography of raw garlic extract. Proliferation of murine splenocytes by RGF was assessed by MTT assay. Activation of macrophages in peritoneal exudates cells was followed by the release of nitric oxide (NO) and phagocytosis of yeast cells. RGF stimulated murine splenocytes to a similar extent as seen in the case of established polysaccharide immunostimulators (galactan, arabinogalactan, mannan and zymosan); 4-5 fold stimulation was seen compared to untreated cells (p<0.01). Further, RGF activated macrophages present in rat peritoneal exudates to release NO which was significant at both 24 h and 48 h (p<0.01). Yeast cell phagocytosis by activated macrophages was significantly enhanced (p<0.05) by RGF in comparison to untreated cells. In conclusion, RGF causes significant immunostimulation of murine lymphocytes and macrophages in vitro. Since fructans are present in abundance in raw garlic, it appears to be promising for the development of functional foods for immunomodulation by its inclusion in processed foods.