Plant-Derived Polyphenols Interact with Staphylococcal Enterotoxin A and Inhibit Toxin Activity

Abstract

This study was performed to investigate the inhibitory effects of 16 different plant-derived polyphenols on the toxicity of staphylococcal enterotoxin A (SEA). Plant-derived polyphenols were incubated with the cultured Staphylococcus aureus C-29 to investigate the effects of these samples on SEA produced from C-29 using Western blot analysis. Twelve polyphenols (0.1-0.5 mg/mL) inhibited the interaction between the anti-SEA antibody and SEA. We examined whether the polyphenols could directly interact with SEA after incubation of these test samples with SEA. As a result, 8 polyphenols (0.25 mg/mL) significantly decreased SEA protein levels. In addition, the polyphenols that interacted with SEA inactivated the toxin activity of splenocyte proliferation induced by SEA. Polyphenols that exerted inhibitory effects on SEA toxic activity had a tendency to interact with SEA. In particular, polyphenol compounds with 1 or 2 hexahydroxydiphenoyl groups and/or a galloyl group, such as eugeniin, castalagin, punicalagin, pedunculagin, corilagin and geraniin, strongly interacted with SEA and inhibited toxin activity at a low concentration. These polyphenols may be used to prevent S. aureus infection and staphylococcal food poisoning.

Fig 1. Growth effect of polyphenols on SEA-producing strain.

(A) hydrolyzable tannins and (B) procyanidins. Values represent the mean ± SD for three independent experiments. The final concentration of polyphenol (mg/mL) is indicated between brackets.

Fig 2. Western blot analysis of the influence of polyphenols on SEA production.

(A) hydrolyzable tannins and (B) procyanidins. Values represent the mean ± SD for three independent experiments. * represents p < 0.05 compared to control, and ** represents p < 0.01 compared to control.

Fig 3. Direct reactivity of polyphenols to SEA.

(A) hydrolyzable tannins (0.25 mg/mL) and (B) procyanidins (0.25–0.50 mg/mL). Values represent the mean ± SD for three independent experiments. * represents p < 0.05 compared with the control. (); final concentration (mg/mL).

Fig 4. Inhibitory effect of polyphenols on the toxic activity of SEA against spleen cells.

Values represent the mean ± SD for three independent experiments. * Represents p < 0.05 compared with the SEA (+) control. (); final concentration (μg/mL).

Fig 5. Affinity interaction of staphylococcal enterotoxin A (SEA) and hydrolyzable tannins.

1; eugeniin, 2; castalagin, 3; punicalagin, 4; pedunculagin, 5; corilagin, 6; geraniin, 7; penta-galloyl-glucose, 8; sanguiin H-6, and 9; tannic acid. For the definition affinity interaction unit (AIU), see the Materials and methods section.