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# Phenolic extracts of bilberry: they protect lipid from oxidation in in vitro simulated digestion conditions

Oana-Crina Bujor, Christian Ginies, Valentin I. Popa, Claire Dufour

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## ► To cite this version:

Oana-Crina Bujor, Christian Ginies, Valentin I. Popa, Claire Dufour. Phenolic extracts of bilberry: they protect lipid from oxidation in in vitro simulated digestion conditions. ICP 2016 - XXVIIIth International Conference on Polyphenols, Jul 2016, Vienna, Austria. 2016. hal-01608682

HAL Id: hal-01608682

https://hal.science/hal-01608682

Submitted on 2 Jun 2020

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## BACKGROUND

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**Extracts of bilberry stems, leaves and fruits:**

**Can they protect dietary lipids from oxidation during digestion in *in vitro* conditions?**

**Bilberry (BB) (Vaccinium myrtillus L.) polyphenols: content and main contributors [3]**

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## MATERIALS AND METHODS

### In vitro model of gastric digestion [4]

BB samples
from July 2013

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Leaves

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Stems

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Fruits

1. Microwave-assisted
extraction
(1% citric acid in water
or 55% aq. EtOH
(fruits only)

2. Dried Extracts (DE)

[0.1 mg DE/mL]

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[0.2 mg DE/mL]

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Metmyoglobin
[20 µM]final

37 °C, 6 h

Lipid-derived
conjugated dienes
(CDs)
Abs. at 234 nm

oil-in-water Emulsion stabilized by:

- BSA (Bovine Serum Albumin)

- PL (egg yolk phospholipids)

### In vitro model of oro-gastrointestinal digestion [5]

<table><thead><tr><th>Oral Phase</th><th>Gastric Phase</th><th>Intestinal Phase</th></tr></thead><tbody><tr><td>Mix:<br>dietary lipids<br>(BSA or PL emulsions)<br>+</td><td>Oral phase<br>(1:1 dilution with SGF)<br>+</td><td>Gastric phase<br>(1:1 dilution with SIF)<br>+</td></tr><tr><td>Leaf extract (36 mg)<br>+</td><td>pepsin (2000 U/mL)<br>+</td><td>pancreatin (100 U/mL)<br>+</td></tr><tr><td>CaCl<sub>2</sub> (0.75 mM)<br>↓</td><td>MbFe<sup>II</sup> (20 µM)<br>↓</td><td>bile (10 mM)<br>+</td></tr><tr><td>Adjustment pH 7:<br>1 M NaOH<br>↓</td><td>Adjustment pH 5:<br>1 M HCl<br>↓</td><td>CaCl<sub>2</sub> (0.49 mM)<br>↓</td></tr><tr><td>Incubation:<br>5 min, 37 °C, 130 rpm<br>↓</td><td>Incubation: → Sampling:<br>1 h, 37 °C, 280 rpm; 0, 30, 60 min<br>↓</td><td>Adjustment pH 6.5:<br>1 M NaOH<br>↓</td></tr><tr><td>No sampling<br>↓</td><td>Adjustment pH 3:<br>1 M HCl<br>↓</td><td>Incubation:<br>2 h, 37 °C, 280 rpm<br>↓</td></tr><tr><td></td><td>Incubation: → Sampling:<br>1 h, 37 °C, 280 rpm; 90, 120 min<br>↓</td><td>Sampling:<br>0, 30, 60, 90, 120 min<br>↓</td></tr><tr><td></td><td>Determination of CDs</td><td>Determination of CDs</td></tr></tbody></table>

## CONCLUSIONS

Leaf, stem and fruit extracts of bilberry can play a protective role towards oxidation of polyunsaturated dietary lipids during digestion.

The fast lipid oxidation in the gastric step (BSA and PL emulsion systems) and the slower lipid oxidation in the intestinal step (PL system) were totally inhibited by a bilberry leaf extract at the level of 3 mg/mL in the gastric step.

→ the stability of the phenolic compounds should be further evaluated in the gastrointestinal digestion to give an insight into their protective mechanisms.

## RESULTATS AND DISCUSSIONS

### Gastric digestion: Inhibition of lipid oxidation

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✓ Extracts from leaves and stems appear similarly efficient at inhibiting metmyoglobin-initiated lipid oxidation in both BSA- and PL-stabilized emulsions at pH 5 (49-73%). Leaves containing 75% (w/w) in chlorogenic acids proved to be the best antioxidant extract in the BSA model.

✓ Extracts from fruit were added at twice the level compared to stem and leaf.

→ Extract with 55% aq. EtOH has a higher content in phenolic compounds and is also more efficient than the aqueous fruit extract.

✓ Leaf and stem extracts have no ability to inhibit lipid oxidation at pH 3 in PL model (data not shown)

NB: standards were used at 100 µM levels.

### Oro-gastrointestinal digestion: Inhibition of lipid oxidation

#### ✓ In BSA-stabilized emulsions

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✓ Gastric step: fast lipid oxidation between t0 and 120 min → metmyoglobin was likely the prooxidant form for the 1st hour when hematin may be released from MbFeII during the 2nd hour. The leaf extract at a dietary concentration (3 mg/mL) totally inhibited lipid oxidation.

✓ Intestinal step: weak increase in CD levels from 162 to 226 µmol/g lipids over the two hours of study. Inhibition by the stem extract is kept.

#### ✓ In PL-stabilized emulsions

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✓ Gastric step: lipid oxidation was 2-fold slower than in the BSA model. Totally inhibited by the stem extract.

✓ Intestinal step: weak lipid oxidation. Antioxidant action of the leaf extract preserved.

**References:**

[1] Pérez-Jiménez J. et al., Am. J. Clin. Nutr., 2011, 93, 1220-8.

[2] Ursini F. and Sevanian A., Biol. Chem., 2002, 383, 599-605.

[3] Bujor et al., Food Chem, submitted.

[4] Lorrain et al., J Agric Food Chem., 2012, 60, 9074-9081.

[5] Minekus M. et al., Food & Function, 2014, 5, 1113-24.M

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