In Vitro Antimicrobial and Cytotoxic Activities of Verbena officinalis L. Extracts: Preliminary Screening and Dose–Response Evaluation in MCF-7 Breast Cancer Cells Antimicrobial and Cytotoxic Activities

Abstract

Background: Verbena officinalis L. is a medicinal plant with a variety of secondary metabolites and described biological activities. Although previous investigations have demonstrated antimicrobial and antiproliferative properties of preparations derived from V. officinalis, biological responses may vary considerably depending on polarity of the solvent, extraction conditions and experimental models. Further evaluation of various plant extracts could help to understand their possible biological activities.
Objective: The objective of this study was to evaluate concentration dependent cytotoxic responses of MCF-7 human breast cancer cells after exposure to hexane and ethyl acetate fractions and to study the antimicrobial activity of aqueous and methanolic extracts of V. officinalis against selected microorganisms. Materials and Methods: Aqueous and methanolic extracts were prepared from the leaves and stems of V. officinalis. Antimicrobial activity was assessed using the agar-well diffusion method against Staphylococcus aureus, Streptococcus sobrinus, Klebsiella pneumoniae, and Candida albicans at nominal extract concentrations of 12.5%, 25%, 50%, and 100%. The cytotoxic responses of MCF-7 cells were evaluated using the MTT assay following exposure to hexane and ethyl acetate fractions at concentrations ranging from 10 to 300 µg/mL, with vincristine included as a reference treatment. The available data were evaluated using descriptive statistics and exploratory concentration–response modeling. Results: The aqueous extract produced inhibition zones of 13–14 mm against S. aureus and 13–15 mm against S. sobrinus at the two highest tested concentrations. The methanolic extract produced inhibition zones of 13–15 mm against S. sobrinus. No measurable inhibition was reported against K. pneumoniae or C. albicans. In the MTT assay, both plant fractions demonstrated concentration-associated inhibition of MCF-7 cellular metabolic activity. At 300 µg/mL, mean inhibition reached 63.6% for the hexane fraction and 49.6% for the ethyl acetate fraction, compared with 93.9% for vincristine. Calculated IC50 values IC50 values were 234.99 µg/mL for hexane, 274.10 µg/mL for ethyl acetate, and 21.25 µg/mL for vincristine. Exploratory reanalysis yielded different apparent IC50 estimates, particularly for the ethyl acetate fraction. Conclusion: It was shown that under the conditions of the experiment the preparations of verbena officinalis had a selective antimicrobial action and inhibited the metabolic activity of MCF-7 cells depending on the concentration. Overall, the hexane fraction showed more inhibition than the ethyl acetate fraction. These preliminary results are an incentive for further standardized studies to assess the biological significance and repeatability of the responses found.