Biotransformation Strategy To Reduce Allergens in Propolis

DOI: 10.1128/AEM.00811-12

Article Figures & Data

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Fig 1
Structural formulas of the molecules constituting the allergenic fraction of propolis. The arrow indicates the chemical bond hydrolyzed by cinnamoyl esterase activity.
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Fig 2
Degradation of caffeic acid esters in raw propolis samples by increasing concentrations of L. helveticus MIMLh5 cells. Propolis was dispersed in PBS buffer plus 10% ethanol or 50% PEG 400. The data are reported as means (three experiments) of the relative amount of all caffeates shown in Fig. 1 ± standard deviations.
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Fig 3
Relative amounts of allergenic esters of caffeic acid in propolis treated with L. helveticus strains. The names of the molecules match those in Fig. 1. The amount of each molecule in the control sample (propolis incubated without bacteria) was set to 100.

Table 1

Concentrations of allergenic caffeic acid esters and flavonoids in the Italian propolis employed in our study

Molecule or parameter	Concn^a
	Control	Biotransformation with 2 × 10⁹ MIMLh5 cells g⁻¹
	Control	10% ethanol	50% PEG 400
3M3	2.66 ± 0.11	1.69 ± 0.10	1.53 ± 0.10
3M2	4.33 ± 0.19	2.53 ± 0.14	2.41 ± 0.14
2M2	2.43 ± 0.13	1.52 ± 0.10	1.35 ± 0.09
CABE	6.76 ± 0.41	4.83 ± 0.30	4.36 ± 0.30
CAPE	34.62 ± 1.42	26.01 ± 1.12	21.84 ± 1.10^b
Total amt	50.80 ± 2.59	36.58 ± 1.91	31.50 ± 1.73^b
Total flavonoids	208.00 ± 11.90	204.00 ± 12.64	212.00 ± 13.81
Flavonoid esters	46.00 ± 2.44	45.08 ± 2.44	46.80 ± 2.55
Caffeic acid	3.80 ± 0.17	4.40 ± 0.19	4.51 ± 0.22

↵a Data are shown as mg of molecule per g of propolis and describe experiments carried out using 2 × 10⁹ cells of MIMLh5 to treat 1 g of propolis dispersed in 10% ethanol or 50% PEG 400. The data represent the means of at least three independent experiments ± standard deviations. With the exception of total flavonoids and flavonoid esters, all molecule concentrations were significantly modified by the biotransformation (P < 0.001; unpaired Student's t test).
↵b Statistically significant difference between PEG- and ethanol-treated propolis (P < 0.05).

Table 2

Flavonoid concentrations corresponding to MIC₅₀s of the propolis preparations

Microorganism	Concn of flavonoids in preparation to achieve MIC₅₀ (mg ml⁻¹)^a		P^b
Microorganism	Conventional propolis	MIMLh5-treated propolis	P^b
S. aureus	1.50 ± 0.52	1.04 ± 0.28	0.08
S. haemolyticus	1.00 ± 0.35	0.87 ± 0.35	0.28
S. pneumoniae	0.26 ± 0.09	0.26 ± 0.07	1.00
C. albicans	3.00 ± 1.04	2.55 ± 0.94	0.42
C. tropicalis	2.55 ± 0.94	2.7 ± 0.78	0.42

↵a The means (± standard deviations) of three independent experiments are shown. Ethanol solutions, tested as a control, did not affect microbial growth.
↵b The P values refer to the statistical difference between the two propolis samples according to an unpaired Student's t test.