Evaluation of Biological Value and Appraisal of Polyphenols and Glucosinolates from Organic Baby-Leaf Salads as Antioxidants and Antimicrobials against Important Human Pathogenic Bacteria

Abstract

The present investigation has been carried out to investigate the biological role of four different types of baby-leaf salads and to study their potential as natural sources of antioxidants and antimicrobials against several isolates from important human pathogenic bacteria. Four single types of salads (green lettuce, red lettuce, rucola and watercress) and two mixtures [(1) red lettuce+green lettuce; (2) green lettuce + red lettuce + watercress + rucola] were assayed. The HPLC analysis revealed interesting levels of polyphenols and glucosinolates. The results showed a significant variation (p < 0.05) of polyphenols and glucosinolates with plant material. Nine different types of polyphenols grouped in three major classes were found: gallic acid, chlorogenic acid, caffeic acid and dicaffeoyltartaric acid (phenolic acids); quercitin-3-O-rutinoside, quercitin-3-O-rhamnoside, luteolin-7-O-glucoside and isorhamnetin (flavonoids); and cyanidin-3-glucoside (anthocyanins). Only three different glucosinolates were found: glucoraphanin; gluconasturtiin and 4-methoxy-glucobrassicin. A positive correlation was detected between polyphenol contents and antioxidant activity. Red lettuce and mixture 1 were the baby-leaf salads with the highest antioxidant potential. As for the antimicrobial activity, the results showed a selective effect of chemicals against Gram-positive and Gram-negative bacteria and Enterococcus faecalis and Staphylococcus aureus were the bacteria most affected by the phytochemicals. Based on the results achieved baby-leaf salads represent an important source of natural antioxidants and antimicrobial substances.

Functionality of Films from Nigella sativa Defatted Seed Cake Proteins Plasticized with Grape Juice: Use in Wrapping Sweet Cherries

“…Such active ingredients in GJ were also expected to disrupt the cell wall of gram-negative bacteria. Gram-negative bacteria have complex cell walls and are more resistant to antimicrobial agents than gram-positive bacteria [87,88]. Similar work has found that gram-positive bacteria were more susceptible to polyphenols than gram-negative bacteria.…”

Exploring Phytochemicals for Combating Antibiotic Resistance in Microbial Pathogens

“…In comparison to ampicillin, which demonstrated MICs of 0.1 and 3.2 μg/ml, Caffeic acid demonstrated an MIC of 1600 μg/ml against E. coli and S. aureus (Lim et al, 2016). Moreover, gallic acid has been shown to exhibit antibacterial properties against Enterococcus faecalis (Aires et al, 2013). It has also showed strong antibacterial potentials against Streptococcus pneumonia, P. aeruginosa, Moraxella catarrhalis, S. aureus, Enterococcus faecalis, E. coli, and Streptococcus agalactiae strains (Cueva et al, 2012).…”

General overview of phenolics from plant to laboratory, good antibacterials or not

“…[ 40 ] Gallic acid is a phenolic acid showing an effect against Enterococcus faecalis . [ 41 ] It also showed the greatest effect, among several phenolic compounds, against a group of bacterial strains including Pseudomonas aeruginosa , S . aureus , Moraxella catarrhalis , E .…”