Context: The data concerning the influence of Plantaginaceae water extracts on bacterial growth are contradictory.
Objective: This study investigates the influence of Plantago maxima Juss. ex Jacq., Plantago lanceolata L., Plantago major L., Veronica teucrium L., Veronica spicata L., and Veronica incana L. aqueous extracts on growth of Escherichia coli K12 culture and the relation to antioxidant, reducing, and iron-binding activities.
Materials and methods: Aqueous extracts were prepared from the dried leaves with the final concentration of 1/10, 1/15, 1/20, 1/25, 1/30, 1/35, and 1/40 (w/w). Comparative analysis of total flavonoids, iridoids, and tannins in Plantaginaceae species was performed. Iron-binding, antioxidant, and reducing activities of plant extracts were analyzed spectrophotometrically. The influence of plant extracts on E. coli K12 growth was studied in vitro by estimating the bacterial growth in the extract-containing medium.
Results: Total tannin content in plant leaves positively correlated with iron-binding activity (r = 0.641), whereas total flavonoids correlated with antioxidant activity (r = 0.687). In an in vitro model, it is estimated that water extracts of studied Plantaginaceae species stimulated bacterial growth. Prebiotic activity significantly of 1/20 and 1/40 plant extracts positively correlated with antioxidant (r = 0.589; r = 0.576, respectively) and reducing activity (r = 0.721; r = 0.620, respectively) of plant aqueous extracts at 6-24 h. Negative correlation was observed between iron-binding activity and bacterial growth (r = -0.503 and r = -0.534 for 1/20 and 1/40 extracts, respectively).
Conclusion: Aqueous Plantaginaceae extracts possess prebiotic activity depending on the phytochemical content of plant leaves.
Keywords: Flavonoids; Plantago; Veronica; iron-binding; prebiotic activity.