Evaluation of the Antimicrobial Potential of Two Flavonoids Isolated from Limnophila Plants

Abstract

The antimicrobial potential of two bioflavonoids, i.e., 5,7-dihydroxy-4',6,8-trimethoxyflavone (1) and 5,6-dihydroxy-4',7,8-trimethoxyflavone (2), isolated from Limnophila heterophylla Benth. and L. indica (Linn.) Druce (Scrophulariaceae), respectively, were evaluated against the microbial strains Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Alternaria solani, and Candida albicans. Compounds 1 and 2 exhibited moderate but broad antimicrobial activities against both Gram-positive and Gram-negative bacteria and also against the fungal pathogens. Moreover, the mechanism of action of 1 and 2 on the cellular functions or structures of some of the microorganisms was studied. Compound 1 showed a bactericidal effect against E. coli and S. aureus (MICs of 200 and 250 μg/ml, resp.), while compound 2 was found to effectively kill B. subtilis by cell lysis. The growth of A. solani and C. albicans was inhibited by compounds 1 and 2, respectively. The effects of the flavonoids on the cellular structures and the carbohydrate metabolic pathways were studied by scanning electron microscopy (SEM) of the treated cells and by assessing the specific activity of key enzymes of the pathways, respectively. At sublethal doses, they enhanced the activity of gluconeogenic fructose bisphosphatase, but decreased the activity of phosphofructokinase and isocitrate dehydrogenase, the key enzymes of the EmbdenMeyerhofParnas pathway and the tricarboxylic acid cycle, respectively.

Antibacterial activity of flavonoids and their structure–activity relationship: An update review

“…aureus , whereas 5,6‐dihydroxy‐4,7,8‐trimethoxyflavone ( 14 ) was found to effectively kill B . subtilis by cell lysis (Brahmachari et al, ). When screening natural products for inhibition of β‐ketoacyl acyl carrier protein synthase (Chitsazian‐Yazdi et al, ), Lee et al () found that the 3,6‐dihydroxyflavone ( 50 ) was very effective.…”

LC-MS/MS Tandem Mass Spectrometry for Analysis of Phenolic Compounds and Pentacyclic Triterpenes in Antifungal Extracts of <em>Terminalia brownii</em> (Fresen)

“…Also 5,7-dihydro-3,4′,6-tri-methoxyflavone, isolated from the Dodonaea angustifolia gave promising growth inhibitory effects against Saccharomyces cerevisiae with the MIC value of 3.9 µg/ml [95]. Moreover, 5,6-dihydroxy-3',4',7-trimethoxyflavone was found to affect the fungal development through disruption of the fungal metabolic pathway and of the fungal cell function [96]. Subsequently, we suggest that 5,6-dihydroxy-3,4,7-trimethoxy flavone (12) in T. brownii stem wood, might have a similar mechanism of action to inhibit fungal growth.…”

Nevadensin: Isolation, chemistry and bioactivity

“…MIC of the compound for E. coli and A. solani were found to be 200 and 250 µg/ml, respectively. [53] Other Activities Brahmachari et al [54] evaluated nevadensin for its cyclooxygenase-1 and 2 (COX-1 and COX-2) inhibitory efficacy by employing the COX catalysed prostaglandin biosynthesis assay in vitro method. The compound was found to exhibit moderate inhibitory activity against COX-1 and weak activity against the COX-2 with respective percent inhibition of 7.37 and 0.65% both at a dose of 10 µM.In addition, pharmacological experiments have shown that the flavonoid possesses expectorant and antitussive actions.…”