Elucidation of Bioactive compounds in flower extracts of Camellia sinensis by HPLC-DAD-MS/MS and their inhibitory effects on replicative bacterial DNA polymerases

Abstract

Camellia sinensis L. (C. sinensis) is an economically valuable crop whose leaves are used to produce tea. Tea flowers extracts (TFE) have been tested for their DNA polymerase inhibitory effect experimentally and in silico. Antioxidant capacities of TFE were determined by their DPPH radical scavenging activities (RSA), total phenolic acid, and flavonoid contents. While methanol extract and its fractions, except the aqueous fraction, showed strong inhibition on Gram (-) DNA polymerase DnaE, ethyl acetate, and butanol fractions showed strong inhibition on Gram (+) DNA polymerase PolC. The fractions had varying degrees of inhibition in tested microorganisms, except Enterococcus faecalis. Bacillus subtilis was the most inhibited microorganism. The binding energies of compounds for both polymerases varied between 5.5 kcal/mol (polC) and - 9.7 kcal/mol (DnaE). Some compounds especially interact with the catalytic aspartic acid amino acids (D973, D975, and D1098) of polC. The ethyl acetate fraction had the best DPPH RSA and the highest total phenolic content. According to HPLC-DADMS/MS analysis, tea catechins corresponded to 58.1% of all phenolics, which comprised 17.9% of the methanol extract. All these results might support the hypothesis of the use of TFE for a potential candidate as a functional food and beverage.