Characterization and quantification of two acylated flavonol glycosides from <i>Camellia sinensis</i> and their antibacterial effect on oral pathogens

Abstract

Acylated flavonol glycosides (AFGs) are a new group of flavonoids with multiple pharmacological functions. In the present work, two AFGs were isolated with a combined chromatography technology from <i>Camellia sinensis</i> and identified as quercetin tetraglycosides with one <i>p</i>-coumaryl moiety (F₁) and kaempferol tetraglycosides with one <i>p</i>-coumaryl moiety (F₂) by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) and nuclear magnetic resonance (NMR). F₁ and F₂ with high purity and quantity can be obtained through relatively simple steps, which is of great significance in industrial production and application. The quantification of two AFGs in different tea cultivars and different season samples was conducted using the high-performance liquid chromatography (HPLC) method. Among fifty tested tea cultivars, the contents of F₁ and F₂ were extremely high in 'Zhenghe Dabaicha' and 'Wannong 95', but these were undetectable in some tea cultivars. Relatively high contents of AFGs were found in autumn harvested tea samples which might be related to sunlight irradiation. Further <i>in vitro</i> experiments showed that F₁ and F₂ monomers were effective on inhibiting growth and biofilm development of <i>Porphyromonas gingivalis</i> and <i>Fusobacterium nucleatum</i>. This antibacterial activity was proven to involve the chelation of iron. These results provide useful information on AFGs-rich tea resources and new insights of AFGs into effective agents against oral diseases.