Coriander, celery and parsley against resistant E. coli: what did the laboratory study prove?

Study card

• Countries: Egypt and Portugal.
• Main institutions: Cairo University, Pharos University in Alexandria, Alexandria Main University Hospital, and LAQV-REQUIMTE at the Faculty of Pharmacy, University of Porto.
• Bacterial isolates: private diagnostic laboratories across Alexandria, Egypt.
• Design: metabolomics plus in-vitro antibacterial and antibiofilm experiments.
• Published: 21 October 2026.
• Journal: BMC Complementary Medicine and Therapies.
• DOI: 10.1186/s12906-026-05610-0. [1]

What was studied?

The researchers compared celery Apium graveolens, coriander Coriandrum sativum and parsley Petroselinum crispum to determine how their chemical profiles differ and whether those differences are associated with activity against multidrug-resistant uropathogenic E. coli and bacterial biofilms. [1]

Where was the work done?

The team included researchers from Pharmacognosy and Pharmaceutical Analytical Chemistry at Cairo University; Microbiology and Immunology and Pharmacognosy/Natural Products at Pharos University in Alexandria; Alexandria Main University Hospital; and LAQV-REQUIMTE at the University of Porto in Portugal. Twenty uropathogenic E. coli isolates came from private diagnostic laboratories across Alexandria. The isolates were anonymized and contained no identifying patient data. [1]

What plant material was tested?

Fresh celery, coriander and parsley were bought in Alexandria. A taxonomist authenticated the plants and voucher specimens were deposited at Cairo University. The aerial parts were dried; 120 g of each plant was extracted with methanol, then partitioned using water and methylene chloride. The experiment therefore tested concentrated solvent extracts, not ordinary food portions. [1]

Chemical analysis

LC-QTOF-MS/MS in positive and negative ion modes and multivariate statistics were used. The study annotated 167 metabolites, including flavonoids, coumarins, phenolic acids, fatty acids, chlorins and amino-acid derivatives. The three herbs produced clearly different chemical fingerprints. [1]

Bacterial testing

The 20 urinary isolates were characterized for antibiotic susceptibility and biofilm formation: 12/20 were strong biofilm formers, four intermediate and four non-biofilm formers. Minimum inhibitory concentrations (MICs) were measured for the plant extracts, and combinations with ciprofloxacin and norfloxacin were tested. [1]

Main results

Coriander was the most active preparation: its total methanolic extract had MIC = 3.75 µg/mL, and the aqueous mother liquor retained the same MIC. Celery’s total methanolic extract had MIC = 50 µg/mL, improving to 25 µg/mL in its aqueous fraction. Parsley showed no detectable activity in the total methanolic extract or aqueous mother liquor, while its methylene-chloride fraction showed weaker activity at 100 µg/mL. [1]

When coriander methanolic extract was combined with ciprofloxacin or norfloxacin, the authors described the interaction as additive, with no evidence of synergy or antagonism. Extracts also reduced biofilm mass under the laboratory conditions. [1]

What does the study not prove?

It does not show that eating coriander, celery or parsley treats a urinary tract infection. The study exposed bacteria outside the body to solvent extracts. It did not measure what concentrations reach human urine after eating the plants, absorption or metabolism, safety of concentrated extracts, or clinical cure.

Strength of evidence

This is a peer-reviewed preclinical study with useful chemical characterization and clinical bacterial isolates, so it is stronger than a simple single-strain screening experiment. But it remains laboratory evidence, not a treatment trial.

It is said… what does the evidence show?

Claim: Because coriander extract inhibited resistant E. coli, coriander can treat UTI.

Verdict: Not supported by this study.

Explanation: The activity came from solvent extracts tested directly on bacteria. No human consumption or patient treatment was studied. [1]

Why is it useful?

The paper identifies extracts and metabolite patterns worth further mechanistic, toxicological and perhaps later animal or clinical investigation. It also illustrates why “the plant” is not one preparation: fresh leaves, food, methanolic extract, aqueous fraction and essential oil are chemically and pharmacologically different.

Funding and conflicts

Open-access publication was supported through Egypt’s Science, Technology & Innovation Funding Authority with the Egyptian Knowledge Bank. The authors declared no competing interests. [1]

Conclusion

The study linked chemical profiles of celery, coriander and parsley to in-vitro activity against multidrug-resistant uropathogenic E. coli. Coriander was the strongest tested extract and antibiofilm effects were observed, but the findings do not show that eating these herbs treats infection or that combining them with antibiotics provides proven clinical synergy.