Short-term heating reduces the anti-inflammatory effects of fresh raw garlic extracts on the LPS-induced production of NO and pro-inflammatory cytokines by downregulating allicin activity in RAW 264.7 macrophages

Scope: Garlic has a variety of biologic activities, including anti-inflammatory properties. Although garlic has several biologic activities, some people dislike eating fresh raw garlic because of its strong taste and smell. Therefore, garlic formulations involving heating procedures have been developed. In this study, we investigated whether short-term heating affects the anti-inflammatory properties of garlic.
Methods and Results: Fresh and heated raw garlic extracts (FRGE and HRGE) were prepared with incubation at 25°C and 95°C, respectively, for 2 h. Treatment with FRGE and HRGE reduced the lipopolysaccharide (LPS)-induced increase in the pro-inflammatory cytokine concentration (TNF-α, IL-1β, and IL-6) and nitric oxide (NO) through heme oxygenase-1 (HO-1) upregulation in RAW 264.7 macrophages. The LPS-induced increase in the concentrations of IL-1β and IL-6, but not TNF-α, were dependent on NO production. The anti-inflammatory effect was greater in FRGE than in HRGE. The allicin concentration measured using 4-mercaptopyridine was higher in FRGE samples than in HRGE samples. Allicin treatment showed reduced production of pro-inflammatory cytokines and NO and increased HO-1 activity.
Conclusion: The results indicate that allicin is responsible for the anti-inflammatory effect of FRGE. Our results suggest a potential therapeutic use of allicin in the treatment of chronic inflammatory disease.

Keywords: allicin / cytokines / garlic / heme oxygenase-1 / nitric oxide