Metabolic perturbations and key pathways associated with the bacteriostatic activity of Clitoria ternatea flower anthocyanin fraction against Escherichia coli

Clitoria ternatea flowers are rich in anthocyanins and possess various biological activities. Specifically, the antibacterial mechanism of action of C. ternatea anthocyanins remains unknown and was investigated in Escherichia coli. Time-kill assay was used to assess the antibacterial activity and the metabolic perturbations in E. coli were investigated utilising LC-MS-based metabolomics. Pathway analyses were carried out for metabolites showing ≥ 2-fold changes. The anthocyanin fraction remarkably reduced the growth of E. coli at 4 h by 95.8 and 99.9% at minimum inhibitory concentration (MIC) and 2 × MIC, respectively. The antibacterial activity of the anthocyanin fraction (MIC) was shown to have perturbed glycerophospholipids (1-Acyl-sn-glycero-3-phosphoethanolamine, phosphatidylglycerol, diacylglycerol and cardiolipin), amino acids (valine, tyrosine and isoleucine) and energy (ubiquinone and NAD) metabolites at 1 and 4 h. This study demonstrated significant metabolic perturbations of the glycerophospholipid, amino acid and energy metabolism being the key pathways involved in the antibacterial activity of anthocyanins from C. ternatea and has promising potential as antibacterial agents for E. coli-related infections.