Isolation and characterization of N-feruloyltyramine as the P-selectin expression suppressor from garlic (Allium sativum).

Garlic (Allium sativum) is a medicinal and culinary plant reported to have several positive health effects on cardiovascular diseases, particularly via suppressing platelet activation. Therefore, active compounds inhibiting platelet activation were isolated from garlic extract using a P-selectin expression suppressing activity-guided fractionation technique. Garlic cloves were extracted with methanol, sequentially partitioned using ethyl acetate, and n-butanol. The ethyl acetate portion was fractionated using silica gel chromatography. The fraction with highest P-selectin expression suppressing activity was further purified using HPLC, and the compounds in the fraction were analyzed using MS, MS/MS, and NMR spectroscopic methods. Using NMR spectroscopy, the compound with highest suppressing activity was confirmed as N-feruloyltyramine. At the concentration of 0.05 microM, N-feruloyltyramine was able to suppress P-selectin expression on platelets by 31% (P < 0.016). Since COX enzymes are deeply involved in the regulation of P-selectin expression on platelets, potential effects of N-feruloyltyramine on COX enzymes were investigated. As expected at the concentration of 0.05 microM, N-feruloyltyramine was found to be a very potent compound able to inhibit COX-I and -II enzymes by 43% (P < 0.012) and 33% (P < 0.014), respectively. N-Feruloyltyramine is likely to inhibit COX enzymes, thereby suppressing P-selectin expression on platelets.