Antibacterial Activity of Some Flavonoids and Organic Acids Widely Distributed in Plants

Abstract

Among natural substances widespread in fruits, vegetables, spices, and medicinal plants, flavonoids and organic acids belong to the promising groups of bioactive compounds with strong antioxidant and anti-inflammatory properties. The aim of the present work was to evaluate the antibacterial activity of 13 common flavonoids (flavones, flavonols, flavanones) and 6 organic acids (aliphatic and aromatic acids). The minimal inhibitory concentrations (MICs) of selected plant substances were determined by the micro-dilution method using clinical strains of four species of pathogenic bacteria. All tested compounds showed antimicrobial properties, but their biological activity was moderate or relatively low. Bacterial growth was most strongly inhibited by salicylic acid (MIC = 250–500 μg/mL). These compounds were generally more active against Gram-negative bacteria: Escherichia coli and Pseudomonas aeruginosa than Gram-positive ones: Enterococcus faecalis and Staphylococcus aureus. An analysis of the antibacterial effect of flavone, chrysin, apigenin, and luteolin showed that the presence of hydroxyl groups in the phenyl rings A and B usually did not influence on the level of their activity. A significant increase in the activity of the hydroxy derivatives of flavone was observed only for S. aureus. Similarly, the presence and position of the sugar group in the flavone glycosides generally had no effect on the MIC values.

Citrus Flavones: An Update on Sources, Biological Functions, and Health Promoting Properties

“…Amongst other flavones widely distributed in fruits, plants, and spices, chrysin and apigenin showed moderate or low antimicrobial properties against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus, the Gram-negative bacteria being more susceptible to the natural compounds. Interestingly, the presence of hydroxyl groups in the phenyl rings A and B did not influence their activity, with the exception of Staphylococcus aureus [91]. On the contrary, Echeverría et al [92] reported that methylation of one hydroxyl group decreased the activity in 3-O-methylgalangin, and methylation of both hydroxyl groups caused inactivation against Bacillus subtilis and Escherichia coli.…”

Quercetin Loaded Monolaurate Sugar Esters-Based Niosomes: Sustained Release and Mutual Antioxidant—Hepatoprotective Interplay

“…These niosomes showed higher hepatoprotective effect compared to free quercetin in vivo, measuring serum biomarker enzymes (i.e., alanine and aspartate transaminases (ALT and AST)) and serum biochemical parameters (i.e., alkaline phosphatase (ALP) and total proteins), while following the histopathological investigation. This study confirms the ability of quercetin loaded niosomes to reverse CCl 4 intoxication and to carry out an antioxidant effect.Pharmaceutics 2020, 12, 143 2 of 18 and anticancer activities [1][2][3]. These intrinsic properties, together with their biocompatibility and remarkable antioxidant activity, have attracted researchers' attention to explore potential therapeutic applications [4,5].Quercetin (3, 30, 4, 5, 7-pentahydroxyflavone) is probably the most studied bioflavonoid, belonging to the family of flavonols; its therapeutic applications include hepatoprotection [6], prevention of neural cell apoptosis [7] and cancer chemo-prevention and treatment [8].Quercetin acts as strong antioxidant by scavenging free radicals and transition metal ions, thus decreasing the process of lipid peroxidation, which is responsible for the development of many diseases, e.g., cardiovascular and neurodegenerative diseases, as well as liver damage [9][10][11].However, quercetin therapeutic applications present challenges due to (i) low aqueous solubility, (ii) photo and oxidative degradability, (iii) high first-pass effect, (iv) poor intestinal absorption and, hence, low systemic bioavailability [12][13][14][15].In order to overcome these problems, which are common among flavonoids, drug delivery systems (DDS) including emulsions, cyclodextrins, polymeric nanoparticles, micelles and liposomes have been used to enhance their pharmaceutical properties [16][17][18].Out of various DDS, niosomes are similar to liposomes in structures, preparation techniques, and physical properties.…”

“…Pharmaceutics 2020, 12, 143 2 of 18 and anticancer activities [1][2][3]. These intrinsic properties, together with their biocompatibility and remarkable antioxidant activity, have attracted researchers' attention to explore potential therapeutic applications [4,5].…”

Phytochemical Screening, Antioxidant, Antibacterial, Antifungal Potential and in vivo Acute Toxicity of the Crude Extract of Cordia Rothii and Viola Serpens

“…Presently, a rapid increase in the number of studies on medicinal plants due to presence of phenolic, avonoid, and phenolic acid compounds which have been observed owing to antioxidant and antibacterial activities (35). These phytochemical contents diverge depending on the plant's species, tissue, developmental stage, and environmental factors, such as temperature, water stress, and light conditions (3,36).…”

“…Mostly avonoids occur as aglycones and glycosylated and methylated derivatives, while glycosylated avonoids are abundant in the human daily diet (41)(42)(43). Moreover, avonoid makes a complex with extracellular or soluble proteins of bacterial cell walls (lipophilic) and may also disrupt bacterial membrane (35,44). Our results showed that both extracts contained much quantity of avonoid contents but CR extract (183.60 ± 4.06), has higher capacity as compared to VS (101.24 ± 2.09).Furthermore, another method is the DPPH-assay, based on the principle that any substance capable of donating hydrogen/an electron, so antioxidant potency is veri ed through DPPH method.…”