ESI-TOF MS analysis and DNA cleavage activity of rutin–metal complexes in aqueous extracts of medicinal plants†
Rutin is a widely used natural antioxidant and possesses metal ion chelation properties. We used high performance liquid chromatography (HPLC) to analyze rutin in samples from four medicinal plants, obtained from the dissolution of aqueous extracts in two different solvents. The results showed that the peak areas for rutin in the samples dissolved in 15% formic acid–methanol were significantly larger than those from the samples dissolved in methanol alone, with increases in the peak area being 222.68% (Sophorae Flos), 125.50% (Lonicerae Japonicae Flos), 24.81% (Forsythiae Fructus), and 200.47% (Violae Herba). Therefore, HPLC was used to measure the changes in the rutin content before and after the reactions of rutin with eight common trace metal elements (calcium, magnesium, zinc, iron, copper, nickel, manganese, and strontium) in hot water. The results showed that the ability of rutin to form complexes was the strongest with iron, followed by strontium and copper. In addition, electrospray ionization-time of flight mass spectrometry analysis performed on rutin–metal ion reaction supernatants revealed that rutin could form complexes at different ratios with the eight different types of metal ions. Measurements of DNA cleavage activity showed that the rutin–copper complex led to dose- and time-dependent DNA cleavage through oxidative damage, which was not observed when rutin alone was reacted with DNA. The aforementioned results indicate that the organic constituents of plants form complexes with trace metal elements during the water decoction process, contributing to their health promoting and disease treatment effects.