Oxidative stress caused by the production of excess nitric oxide (NO) during infection or inflammation has been implicated in the pathogenesis of several diseases, including cancer, diabetes and renal disease. Accordingly, the scavenging of NO radical or/and suppression of NO production by mitogen-activated cells may be promising indicators in screening healthy food. In this work, the NO-scavenging and NO-suppressing activities of different herbal teas were determined and compared with those of green tea. All of the tested herbal teas revealed NO-scavenging and NO-suppressing activities. The NO-scavenging activity of herbal teas can be ranked by the IC50, the concentration of the tested herbal tea required to quench 50% of NO radicals released by sodium nitroprusside. The activities follow the order: green tea > rosemary, sweet osmanthus, rose and lavender > jasmine, lemongrass and daisy. The NO-suppressing activity was evaluated, based on the suppressing effect of herbal teas on the production of NO by LPS-activated RAW 264.7 macrophages. Experimental results indicated that green tea and rosemary had IC50 values of less than 500 μg/ml, and were proven to be good NO-suppressors, whereas lavender, sweet osmanthus, lemongrass, rose, daisy and jasmine had IC50 values that exceeded 500 μg/ml, and were classified as rather poor NO-suppressors. In conclusion, consumption of herbal teas promotes the NO-scavenging and NO-suppressing activities of the diet, even though their activities are weaker than that of green tea.
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