Anti-Acinetobacter baumannii activity of Rumex crispus L. and Rumex sanguineus L. extracts

Objective: To examine the effect of Rumex crispus(R. crispus) and Rumex sanguineus(R. sanguineus) plant extracts against isolates of Acinetobacter baumannii(A. baumannii) from wounds, including multidrug-resistant strains. Methods: Six prepared Rumex extracts were subjected to liquid chromatography-tandem mass spectrometry. Antimicrobial activity of extracts and pure compounds(catechin, quercetin, isoquercitrin, emodin, and gallic acid) was examined by a microtiter plate method, while for determination of compound binary combinations activity a checkerboard method was applied. Active fractions of extracts were detected by agar-overlay high-performance thinlayer chromatography-bioautography assay followed by liquid chromatography-diode array detection-mass spectrometry analysis. Results: A total of 28 compounds were detected in two extracts of R. crispus and 26 compounds in four different R. sanguineus extracts, with catechin as a dominant component. Anti-A. baumannii activity was confirmed for all six R. sanguineus and R. crispus extracts at the concentration range from 1 to 4 mg/mL. Neither examined single compounds nor their binary combinations exhibited an anti-A.baumannii activity(MIC>256 μg/mL). The bioautography showed that fractions with the most prominent anti-A. baumannii activity tended to contain more polar compounds, predominantly flavonol(quercetin and kaempherol) glycosides; but also fractions containing flavanone(eriodictyol) glycosides and anthraquinone(emodin) glycosides; and less polar eriodictyol aglycone. Conclusions: The results justify and elucidate the traditional application of R. sanguineus and R. crispus extracts for wound healing, indicating the necessity for their further examination in combat against multidrug-resistant A. baumannii isolates from wounds.