A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains

Abstract

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL−1. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL−1 biopolymer concentration affording complete killing of the bacterial cells. Insights into the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance since citrus IntegroPectin biomaterials are also devoid of cytotoxic activity, as already shown for lemon IntegroPectin, opening the route to the development of new medical treatments of polymicrobial infections unlikely to develop drug resistance.

Volatile Compounds of Lemon and Grapefruit IntegroPectin

“…Dried samples of lemon and grapefruit IntegroPectin were obtained as previously reported [10]. The divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS, 50/30 μm) fiber was obtained from Supelco (Bellefonte, USA).…”

“…Lemon IntegroPectin, namely citrus pectin extracted from wet industrial waste lemon peel using again HC, has exceptional antioxidant [8] and good antibacterial [9] properties, whereas grapefruit IntegroPectin is a broad-spectrum bactericidal agent currently investigated as a natural antimicrobial likely to drive no antimicrobial resistance [10]. It is also important, in sight of medical applications of these new pectins [11,12], that lemon IntegroPectin is highly cytoprotective, preventing oxidative degradation of human pulmonary cells from oxidizing agents even at high concentrations of a strong oxidizer such as H2O2 [8].…”

“…Aiming to explain the high antimicrobial activity of lemon and grapefruit IntegroPectin, we ascribed the activity to the synergistic action of the chemical structure of citrus pectin extracted using cavitation, combined with the action of citrus terpenes and flavonoids adsorbed across the pectic polymer obtained upon lyophilization of the aqueous extract [10]. In this study we report the analysis of the volatile compounds in both lemon and grapefruit IntegroPectin using the headspace solid-phase microextraction (HS-SPME) technique combined with gas chromatography-mass spectrometry (GC-MS).…”

Pectin: A Long‐Neglected Broad‐Spectrum Antibacterial

“…[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.…”

“…suspended in water only, followed by freeze-drying, afford pectins embedding bioactive phytochemicals such as polyphenols, flavonoids, terpenes and phenolic acids. The resulting pectins offer a large potential in terms of synergistic physiological and biological activity [38,41] which remains largely untapped and represents a new and highly promising area of research in the life sciences and in medicine.…”