Relationships Between Bioactive Compound Content and the Antiplatelet and Antioxidant Activities of Six Allium Vegetable Species

Allium sp. vegetables are widely consumed for their characteristic flavour. Additionally, their consumption may provide protection against cardiovascular disease due to their antiplatelet and antioxidant activities. Although antiplatelet and antioxidant activities in Allium sp. are generally recognised, comparative studies of antiplatelet and antioxidant potency among the main Allium vegetable species are lacking. Also, the relationship between organosulfur and phenolic compounds and these biological activities has not been well established. In this study, the in vitro antiplatelet and antioxidant activities of the most widely consumed Allium species are characterised and compared. The species total organosulfur and phenolic content, and the HPLC profiles of 11 phenolic compounds were characterised and used to investigate the relationship between these compounds and antiplatelet and antioxidant activities. Furthermore, antiplatelet activities in chives and shallot have been characterised for the first time. Our results revealed that the strongest antiplatelet agents were garlic and shallot, whereas chives had the highest antioxidant activity. Leek and bunching onion had the weakest both biological activities. Significantly positive correlations were found between the in vitro antiplatelet activity and total organosulfur (R=0.74) and phenolic (TP) content (R=0.73), as well as between the antioxidant activity and TP (R=0.91) and total organosulfur content (R=0.67). Six individual phenolic compounds were associated with the antioxidant activity, with catechin, epigallocatechin and epicatechin gallate having the strongest correlation values (R>0.80). Overall, our results suggest that both organosulfur and phenolic compounds contribute similarly to Allium antiplatelet activity, whereas phenolics, as a whole, are largely responsible for antioxidant activity, with broad variation observed among the contributions of individual phenolic compounds.