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

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 significantly reduced the LPS-induced increase in the pro-inflammatory cytokine concentration (TNF-α, IL-1β, and IL-6) and NO through HO-1 upregulation in RAW 264.7 macrophages. The anti-inflammatory effect was greater in FRGE than in HRGE. The allicin concentration was higher in FRGE than in HRGE. Allicin treatment showed reduced production of pro-inflammatory cytokines and NO and increased HO-1 activity. The results show that the decrease in LPS-induced NO and pro-inflammatory cytokines in RAW 264.7 macrophages through HO-1 induction was greater for FRGE compared with HRGE. Additionally, 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.