Grapefruit Seed Extract for Antimicrobial Properties

Research suggests that grapefruit seed extract (GSE) possesses broad-spectrum antimicrobial properties, with studies demonstrating activity against gram-positive and gram-negative bacteria, the yeast Candida albicans, foodborne pathogens such as Salmonella Typhimurium and Listeria monocytogenes, and certain viruses including a surrogate norovirus and, in preliminary in vitro testing, SARS-CoV-2. The available evidence comes primarily from laboratory-based studies, many of which focus on GSE as an additive in experimental food packaging films made from various polymers, as well as from formulation research exploring its use as a natural preservative in pharmaceutical gels and nasal sprays. One study observed that GSE disrupts bacterial cell membranes and can be selectively bactericidal at concentrations non-toxic to human cells, though higher concentrations do show cytotoxicity. A significant limitation across this body of evidence is that a substantial portion of commercially available GSE products have been found to be adulterated with undeclared synthetic preservatives such as benzethonium chloride and benzalkonium chloride, raising serious questions about whether the antimicrobial activity observed in studies using commercial GSE products reflects the natural grapefruit compounds themselves or the presence of these synthetic additives — a distinction that remains inadequately resolved in much of the published literature.