Aquo-ethanolic extract of Camellia sinensis (PTRC-31911-A), standardized using Fourier transform infrared analysis, was found to have seven common functional groups in comparison with pre-identified marker compound ‘quercetin’. Phyto-chemical quantitation analysis revealed the presence of 10.65 μg/mg of flavonoids. The bioactivity fingerprint profile of PTRC-31911-A includes IC50(Hydroxyl radical site specific scavenging) = 11.36 ± 0.5 μg/mL, IC80(Hydroxyl radical non-site specific scavenging) = 26.44 ± 0.5 μg/mL and IC50 (Superoxide ion scavenging) = 10.141 ± 0.5 μg/mL. The drug combination analysis of PTRC-31911-A with five third-line antibiotics was carried out against carbapenem-resistant Escherichia coli. The analysis of combination of PTRC-31911-A (6.25–1000 μg/mL) and antibiotics (6.25–1000 μg/mL) revealed synergistic behaviour (fractional inhibitory concentration indices < 1) with tigecycline, ertapenem, meropenem, colistin and augmentin. The lead combination of PTRC-31911-A + ertapenem or meropenem showed maximum augmentative potential at 50 and 100 μg/mL, respectively, with nearly five-fold decrease in minimum inhibitory concentrations as compared with respective antibiotics alone. The synergistic effects implied that the antibacterial combinations of PTRC-31911-A and ertapenem, meropenem, colistin, tigecycline or augmentin would be more effective than a single monotherapy with either of the antibacterial agent. Copyright © 2015 John Wiley & Sons, Ltd.