Nitric Oxide-scavenging Activity of Okinawan Sweet Potato (Ipomoea batatas L.) Leave Extracts

Abstract

Leaves of nine Okinawan sweet potato cultivars (Ipomoea batatas L.) and two comparable sweet potato cultivars were examined for their ability to induce nitric oxide (NO) production in LPS-stimulated RAW264.7 macrophages. All of these varieties suppressed nitrite production, an index of NO. In addition, the sweet potato leave extracts decreased the amount of nitrite ions generated from NOR3, an NO donor, indicating that they have NO-scavenging activity. This NO-scavenging activity of sweet potato leaves was correlated with the total amount of polyphenol and its main constituents of caffeoylquinic acid (CQA) derivatives, such as 5-monoCQA, 4,5-diCQA, 3,5-diCQA, 3,4-diCQA and 3,4,5-triCQA. Therefore, the CQA derivatives may be responsible for the NO-scavenging activity. This study demonstrated that sweet potato leaves may be promising functional food materials for preventing various inflammatory diseases that cause excess NO production.