Towards a new treatment against polymicrobial infections: high antibacterial activity of lemon IntegroPectin againstPseudomonas aeruginosaandEscherichia coli

Abstract

Lemon IntegroPectin obtained via hydrodynamic cavitation of waste lemon peel in water only shows high antibacterial activity against two Gram-negative bacteria, Pseudomonas aeruginosa and Escherichia coli. The antibacterial effect against the ubiquitous pathogen P. aeruginosa was evaluated in terms of the minimal bactericidal (MBC) and minimal inhibitory concentration (MIC). Preliminary insight on the antibacterial mechanism of IntegroPectin originates from investigating its inhibitory activity against E. coli. Given the non-cytotoxic nature of citrus IntegroPectin and the ease of its reproducible production in large amounts, the route is open to the industrial development of a new antimicrobial treatment against polymicrobial infections unlikely to develop drug resistance.*Corresponding authors [a]

A new water-soluble bactericidal agent for the treatment of polymicrobial infections

“…The antibacterial action of this new class of materials is not limited to P. aeruginosa or to S. aureus. For example, closely related lemon IntegroPectin has strong antibacterial activity against Escherichia coli [78]. In the era of antimicrobial resistance, biobased grapefruit IntegroPectin can be considered a promising alternative to antibiotics thanks to its non-cytotoxicity (already shown with epithelial human cells for lemon IntegroPectin [79]) and to multiple modes of action against pathogenic bacteria, making unlikely the development of drug resistance.…”

Pectin: A Long‐Neglected Broad‐Spectrum Antibacterial

“…[21] Using a new form of citrus pectin extracted and isolated from waste citrus peel under acid-free conditions by hydrodynamic cavitation in water followed by freeze drying,freezedrying scholars in Italy first confirmed the broad spectrum activity of pectin against both Gram-positive and Gram-negative ubiquitous pathogens such as S. aureus [33] and and P. aeruginosa. [34] Later, they extended the approach to grapefruit IntegroPectin providing the first insight on the antibacterial mechanism of this new form of pectic material interacting with the cell membrane of S. aureus and P. aeruginosa strains. [38] Due to its proven immunomodulating, anti-inflammatory, antioxidant, hypolipidemic, antidiabetic, anticarcinogenic, antitussive, gastroprotective, and wound-healing properties, pectin has recently been termed "a universal medicine" [39] by scholars in Russia reviewing the medical uses of pectin in medicine, both as therapeutic substance as well as a biomaterial for regenerative medicine and biomedical engineering.…”

“…Lemon IntegroPectin obtained by hydrodynamic cavitation of waste lemon peel in water only shows high antibacterial activity against both Gram-positive bacterial strains of S. aureus [33] and against Gram-negative bacteria such as P. aeruginosa and E. coli. [34] The antibacterial effect of the new IntegroPectin was found to be largely superior to that of commercial citrus pectin. For example, both commercial citrus pectin and lemon IntegroPectin inhibit S. aureus growth ( Figure 5), with a decrease in the number of viable cells in the range 1 to 2 log units, respectively, when the concentration was 3 mg mL À 1 .…”

“…The same ratio holds for the antibacterial effect against the ubiquitous pathogen P. aeruginosa with MIC = 10 mg mL À 1 for lemon IntegroPectin and 20 mg mL À 1 for commercial citrus pectin. [34] However, the minimal bactericidal concentration (MBC, the concentration value for obtaining a total killing effect) of the lemon IntegroPectin against P. aeruginosa is 15 mg mL À 1 , whereas that of citrus pectin is 40 mg mL À 1 , almost three times higher.…”

“…Preliminary insight on the antibacterial mechanism of IntegroPectin from investigating its inhibitory activity against E. coli suggests ( Figure 7) that lemon IntPec at 1.0 mg/mL already after 16 min (~1000 s) the amount of reactive oxygen species (ROS) is higher than that generated by concentrated hydrogen peroxide, to eventually almost double the oxidative stress exerted by H 2 O 2 0.5 M 1.7 h after the addition of the new pectic substance. [34] Dissolved in 1.0 mg/mL concentration this new form of lemon pectin is readily adsorbed at the surface of the microbes where it rapidly drives (after~1000 s) the formation of reactive oxygen species (ROS) in higher amount than that generated by 0.5 M hydrogen peroxide, to eventually almost double the oxidative stress exerted by the latter strong oxidant 1.7 h since the addition of the new pectic substance. [34] In other words, the very same non-cytotoxic pectin showing exceptionally high antioxidant activity expressed by an oxygen radical absorbance capacity (ORAC) value of 122 200 μmol TE/ 100 g (μmol of Trolox equivalents per 100 g of pectin) [32] adsorbed at the surface of a typical Gram-negative bacterium behaves as a strong oxidizer driving formation of high amounts of ROS.…”