Open Access Highly Accessed Research article

Antibacterial activities of almond skins on cagA-positive and-negative clinical isolates of Helicobacter pylori

Carlo Bisignano1, Angela Filocamo1, Erminia La Camera1, Sebastiana Zummo2, Maria Teresa Fera2 and Giuseppina Mandalari13*

Author Affiliations

1 Dipartimento di Scienze del Farmaco e Prodotti per la Salute, University of Messina, Viale Annunziata, Messina, 98100, Italy

2 Dipartimento di Scienze Pediatriche, Ginecologiche, Microbiologiche e Biomediche, University of Messina, Policlinico Universitario, Viale Gazzi, Messina, 98125, Italy

3 The Model Gut, Institute of Food Research, Norwich Research Park, Colney Lane, Norwich, NR4 7UA, UK

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BMC Microbiology 2013, 13:103  doi:10.1186/1471-2180-13-103

Published: 9 May 2013



Helicobacter pylori is known to be a gastric pathogen of humans. Eradication regimens for H. pylori infection have some side effects, compliance problems, relapses, and antibiotic resistance. Therefore, the need for alternative therapies for H. pylori infections is of special interest. We have previously shown that polyphenols from almond skins are active against a range of food-borne pathogens. The aim of this study was to evaluate the antibacterial effects of natural almond skins before and after simulated human digestion and the pure flavonoid compounds epicatechin, naringenin and protocatechuic acid against H. pylori.


H. pylori strains were isolated from gastric biopsy samples following standard microbiology procedures. Also, cagA and vacA genes were identified using PCR. Susceptibility studies on 34 strains of H. pylori, including two reference strains (ATCC 43504, ATCC 49503), were performed by the standard agar dilution method.

Natural almond skin was the most effective compound against H. pylori (MIC range, 64 to 128 μg/ml), followed by natural skin post gastric digestion (MIC range, 128 to 512 μg/ml), and natural almond skin post gastric plus duodenal digestion (MIC range, 256 to 512 μg/ml). Amongst the pure flavonoid compounds, protocatechuic acid showed the greatest activity (MIC range, 128 to 512 μg/ml) against H. pylori strains.


Polyphenols from almond skins were effective in vitro against H. pylori, irrespective of genotype status and could therefore be used in combination with antibiotics as a novel strategy for antibiotic resistance.

Helicobacter pylori; Flavonoids; Almond skins; Epicathechin, Naringerin; Protocatechuic acid