Abstract:
Anti-biofilm represents an urge to face drug resistance. Nymphaea alba L. flowers and rhizomes have
been traditionally used in Ayurvedic medicine for dyspepsia, enteritis, diarrhea and as an antiseptic.
This study was designed to identify the main constituents of Nymphaea alba L. rhizomes and their antibiofilm activity. 70% aqueous ethanolic extract (AEE) of N. alba rhizomes was analyzed by liquid
chromatography, high resolution, mass spectrometry (LC-HRMS) for its phytoconstituents in the
positive and negative modes in addition to column chromatographic separation. Sixty-four phenolic
compounds were identified for the first time in N. alba rhizomes. Hydrolysable tannins represent the
majority with identification of galloyl hexoside derivative, hexahydroxydiphenic (HHDP) derivatives,
glycosylated phenolic acids and glycosylated flavonoids. Five phenolics have been isolated and
identified as gallic acid and its methyl and ethyl ester in addition to ellagic acid and pentagalloyl
glucose. Minimum inhibitory concentrations (MIC) and anti-biofilm activity for the extract and the major
isolated compounds were determined. Radical scavenging activity using 2.2Di (4-tert-octylphenyl)-1-
picryl-hydrazyl (DPPH) assay as well as cytotoxic activity using 3-(4, 5-dimethyl thiazol-2-yl)-2, 5-
diphenyl tetrazolium bromide (MTT) assay have also been evaluated. MIC of N. alba rhizomes against
Staphylococcus aureus was 0.25 mg/mL compared with 0.1 mg/mL for methyl gallate. The best
reduction in biofilm formation (84.9%) as well as the best radical scavenging (IC50 3 µg/mL) and
cytotoxic (IC50 9.61 ± 0.3 µg/mL) activities were observed with methyl gallate. This is the first study for
in-depth characterization of phenolic compounds in N. alba rhizomes revealing it as a valuable source
of phenolic compounds and promising anti-biofilm forming agent of natural origin.
