Abstract: To study the anticoagulant effect of garlic oil, garlic oil was extracted from garlic bulbs in this study and its major chemical components were allyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS) as identified by gas chromatography-mass spectrometry (GC-MS). Experiments in vitro showed that garlic oil, DAS, DADS and DATS partially inhibited thrombin activity, and the inhibitory effect followed the decreasing order: DATS > garlic oil > DADS > DAS. Enzymatic kinetic analysis was carried out using the Lineweaver-Burk double reciprocal plotting method, which showed that garlic oil and its three components inhibited thrombin activity in both competitive and non-competitive mode. Molecular fluorescence analysis revealed that each inhibitor could interact with chromophores in thrombin, resulting in fluorescence quenching. Two-dimensional molecular docking results revealed that DATS could form hydrogen bonds with Asp189, Gly219 and Ala190 in the active site of thrombin and form hydrophobic interactions with Gly216, Ser195 and Trp215 for competitive inhibition; and also form hydrophobic interactions with Gly226, Asp221A, Tyr225, Glu217, Cys191 and Val213 in non-active sites for non-competitive inhibition. Garlic oil and its components exerted their anticoagulant effect by positively four blood coagulation parameters in rats, which decreased in the order of DATS > DADS > DAS > garlic oil. However, they could only weakly enhance antioxidant capacity in rats. Hence, their anticoagulant effect was not correlated with their antioxidant potential.

Key words: garlic oil; sulfide; thrombin; molecular docking; anticoagulant; antioxidant