Structural characterization of chlorogenic acid-metal complexes derived from the aqueous extracts of medicinal plants and their DNA cleavage and antibacterial activities

The discovery of organic components with pharmacological activities in medicinal plants is crucial for new drug development. We examined chlorogenic acid (CGA) using high-performance liquid chromatography to analyze the aqueous and methanolic extracts of medicinal plants dissolved in methanol or methanol containing 15% formic acid. We found that for the aqueous extract, the peak areas of various components dissolved in 15% formic acid methanol were significantly larger than those dissolved in methanol. For the differences in the methanolic extract, the peak areas of all chromatographic peaks were relatively small between the samples dissolved in the two solvents. Electrospray ionization time-of-flight mass spectrometry showed that CGA could react in hot water with the eight most common plant metal ions (Ca 2+ , Cu 2+ , Fe 3+ , Mg 2+ , Mn 2+ , Ni 2+ , Sr 2+ , and Zn 2+ ) to form complexes with different coordination forms. The bioactivity experiments showed that CGA-Cu complexes could cause DNA cleavage through oxidative damage. CGA-Ni, CGA-Mn, and CGA-Zn showed significantly stronger inhibition against Staphylococcus aureus than CGA and the corresponding metal ions. These results suggest that, during the decoction process of medicinal plants, CGA forms complexes with metal ions, which are likely to be one of the active ingredients in medicinal plants. Subsequently, further research is needed on the antibacterial mechanism of chlorogenic acid-metal complexes not mentioned in this article.