Inhibitory effects of food additives derived from polyphenols on staphylococcal enterotoxin A production and biofilm formation by Staphylococcus aureus

Figures & data

Table 1. Food additives derived from polyphenols used in this study.

Abbreviations	Food additives derived from polyphenols	Main polyphenols
TA	Tannic acid AL	Tannic acid (more than 96.0%)
PKT	Purification kaki-tannin	Persimmon-derived polyphenols based on tannins (95.0%)
PP	Purephenon 50 W	EGCg (more than 20.0%), tea-derived polyphenols (more than 50.0%)
SF	Sunfood 100	Tea-derived polyphenols (47.5%), EGCg and ECg (total of more than 26.9%)
POP	Polyphenon 70A	Tea-derived polyphenols (99.3%)
GE	Grape extract HA	Proanthocyanidin (grape juice extract)
GN	Gravinol®-N	Grape seeds-derived proanthocyanidin (42.1%), flavanol (44.1%)
BP	Blackcurrant polyphenol AC10	Delphinidin 3-rutinoside, delphinidin 3-glucoside, cyanidin 3-rutinoside, cyanidin 3-glucoside (total of more than 10.0%)
APL	Applin AFPOMM9051	Apple polyphenol (more than 80.0%)
RT	Resveratrol-P5	Polyphenols (31.8%), Resveratrol (5.1%)
RT-WSP0.5	Resveratrol-WSP 0.5	Polyphenols (3.0%), Resveratrol (0.5%)
GCBE	Green coffee bean extract-P	Chlorogenic acid (25.6%) Chlorogenic acid derivatives (47.5%)
WP	Walnut polyphenol-P30	Walnut polyphenol including pedunclagin (31.0%)
EPE	Evening primrose extract-P	Polyphenols, convert to gallic acid (62.0%)

Fig. 1. Antimicrobial effects of food additives derived from polyphenols on SEA-producing strain Staphylococcus aureus C-29.

Notes: S. aureus C-29 was incubated with 1.0–5.0 mg/mL of 14 food additives derived from polyphenols. After incubation for 1 h, cells were plated and bacteria counted. Values represent the mean ± SD for three independent experiments. ( ); final concentration (mg/mL). The food additives names and their abbreviations are given in Table 1.

Fig. 2. Interaction between food additives derived from polyphenols and cultured staphylococcal enterotoxin A (SEA)-producing strain.

Notes: (A) Staphylococcus aureus C-29 (10³–10⁴ CFU/mL) was cultured with 0.1, 0.25, 0.5, 1.0, 2.5 mg/mL of each sample in BHI broth at 37 °C for 24 h. Following centrifugation, the supernatant was applied to SDS-PAGE and visualized by the Western blot analysis. MilliQ water was performed as a positive control. (B) The relative SEA production rate of SEA protein was determined by the Western blot analysis and quantified using ImageJ software (National Institutes of Health, Bethesda, Maryland, USA). Values represent the mean ± SD for three independent experiments. * represents p < 0.05 compared to the control, ( ); final concentration (mM). The food additives names and their abbreviations are given in Table 1.

Fig. 3. Growth effect of food additives derived from polyphenols on Staphylococcus aureus.

Notes: SEA-producing strain S. aureus C-29 and/or high-biofilm-forming strain S. aureus C-77 was incubated with six food additives derived from polyphenols. After incubation for 24 h (S. aureus C-29) and 48 h (S. aureus C-29 and C-77), cells were plated and bacteria counted. Values represent the mean ± SD for three independent experiments. ( ); final concentration (mg/mL). The food additives names and their abbreviations are given in Table 1.

Fig. 4. Relative gene expression of sea in Staphylococcus aureus C-29 after incubation with food additives derived from polyphenols.

Notes: Samples for RNA extraction were taken at 6 h. Values represent the mean ± SD for three independent experiments. * represents p < 0.05 compared to the control, ** represents p < 0.01 compared to the control, ( ); final concentration (mM). The food additives names and their abbreviations are given in Table 1.

Fig. 5. Inhibitory effect of food additives derived from polyphenols on biofilm formation.

Notes: Staphylococcus aureus C-29 and high-biofilm-forming strain S. aureus C-77 were incubated in 66% TSB broth containing 0.2% glucose with the food additives derived from polyphenols (final concentration of TA, PP, and POP; 0.3, 0.4, 0.5 mg/mL, GN, BP, and RT; 1.0, 2.0, 2.5 mg/mL) at 37 °C for 48 h. Biofilm formation was normalized to the control by crystal violet assay. Values represent the mean ± SD for three independent experiments. * represents p < 0.05 compared to the control, ** represents p < 0.01 compared to the control, ( ); final concentration (mM). The food additives names and their abbreviations are given in Table 1.