Identification, characterization, isolation and activity against Escherichia coli of quince (Cydonia oblonga) fruit polyphenols

Quince fruits are consumed in many parts of Europe and Asia. The polyphenols of the quince fruit were investigated qualitatively by LC–MSn. Thirty-four polyphenols were detected and characterized on the basis of their unique fragmentation pattern in the negative ion mode tandem MS spectra. Nine of them were not reported previously in quince. The crude extract of quince fruit polyphenols showed antibacterial activity against the Gram-negative bacterium Escherichia coli. Five polyphenols, 5-O-caffeoylquinic acid, quinic acid, quinic acid derivative, proanthocyanin B1 and methyl 5-O-caffeoylquinate were isolated and tested for their antibacterial activity. Quinic acid and a quinic acid derivative showed a strong inhibition activity against E. coli. Antibacterial activities were identified using an agar diffusion assay.