Extremely Rare Flavonoid Glycosides Identified in the Stems of Ephedra gerardiana by HPLC-MS and Their Antioxidant Activity.

The plants of the genus Ephedra are mainly known for the contents of alkaloids; however, it has recently been found that they also contain phenolic constituents that show interesting bioactivities, e.g., antioxidative or antimicrobial. From among the Ephedrae herba, the Ephedra gerardiana seems to be relatively poorly researched in terms of flavonoid presence. In this study, on the basis of the results of high-pressure liquid chromatography-mass spectrometry (HPLC-MS) with cone voltage-induced fragmentation analysis, which are discussed in detail, the flavonoid glycosides present in Ephedra gerardiana have been identified. Besides the flavonoids typical of the genus Ephedra, e.g., afzelin, herbacetin 7-O-glucoside, and vicenin-2, compounds that are very rare in nature have been detected as well, namely the p-coumaroyl conjugates of 4'-O-methylafzelin and malonyl flavone C-glycosides. Therefore, Ephedra gerardiana can be regarded as a valuable source of these compounds. Furthermore, the antioxidant activity of the methanol extract indicates that these compounds show potential interesting biological activities.