Enzymatic conversion could boost polyphenol bioavailability

By Stephen Daniells

- Last updated on GMT

Related tags Orange juice Flavonoid

Using enzymes to modify the citrus flavonoid, hesperidin, increases
the bioavailability of the compound by changing the absorption site
in the intestine, say researchers.

The result may eventually lead to a range of functional ingredients with improved bioavailability that "in principle, should work in any food matrix,"​ lead researcher, Dr. Gary Williamson from Nestlé Research Center, told NutraIngredients.com.

Previous studies have reported that hesperidin may provide a range of health benefits such as antioxidant, anti-inflammatory, anticarcinogenic effects and boosting bone health.

However, human studies with orange juice have reported that hesperidin (hesperetin-7-O-rutinoside as it is found naturally in citrus fruit) has limited bioavailability.

The researchers, from the Nestlé Research Center, the Danish Institute for Food and Veterinary Research and France's INRA, used the enzyme hesperidinase, to convert hesperetin-7-O-rutinoside in orange juice into hesperetin-7-glucoside.

A double-blind, placebo-controlled, randomized, 3-treatment crossover study then showed that this change shifted the absorption of the flavonoid from the colon to the small intestine, and resulted in a four-fold increase in plasma hesperidin concentrations relative to untreated orange juice with naturally occurring hesperidin.

There was also a 1.5-fold increase in plasma hesperidin concentrations relative to a hesperetin-7-O-rutinoside-fortified orange juice containing three times more hesperidin than natural orange juice.

The results were published recently in the Journal of Nutrition​ (Vol. 136, pp. 404-408).

Three types of orange juice were prepared: a normal orange juice with natural hesperidin levels (2 mg/kg body weight hesperidin); orange juice treated with hesperidinase enzyme to yield hesperetin-7-glucoside (1.52 mg/kg hesperidin); and orange juice containing deactivated hesperidinase but fortified with hesperidin (giving 6 mg/kg body weight hesperidin).

The low- and high-hesperidin dose levels were equivalent to a 60-kg person consuming 300 and 900 mL, respectively.

The reason behind the shift in absorption site is that hesperetin-7-O-rutinoside is only absorbed in the distal part of the human intestine, after metabolism in the colon by certain strains of bacteria. However, hesperetin-7-glucoside metabolism and subsequent absorption can occur in the small intestine, and absorption into the blood stream is not only quicker but more efficient.

"The results of this study demonstrated that the bioavailability of hesperidin was modulated by enzymatic conversion to hesperetin-7-glucoside, thus changing the absorption site from the colon to the small intestine. This may affect future interventions concerning the health benefits of citrus flavonoids,"​ wrote lead author Inge Lise Nielsen.

Dr. Williamson said that the technique not only means improved absorption of the flavonoid, but also that functional food manufacturers could use less hesperitin (in the glucoside form) and still have bioactive concentrations of hesperidin in circulation.

Although the researchers used orange juice in these experiments, Dr. Williamson said that, in principle, the technique could work in any food matrix, but cautioned: "We have to test this first."

The technique is also not limited to hesperidin but could also be applied to other polyphenols. Indeed, a previous study using quercetin showed that quercetin-3-O-rhamnoglucoside (rutin) from tea was absorbed more slowly than quercetin-4-O-glucoside in onions.

Dr. Williamson told NutraIngredients.com that the main challenge for this technique is ensuring safety, and stressed that the enzyme and corresponding flavonoid glucoside are naturally found in food.

"We are not generating novel compounds,"​ he said.

"You have to make sure that what you use to start with is natural, and what is formed is natural. Making a new compound would mean it becomes a novel food or a drug."

The next stage in this process, said Dr. Williamson, is to examine the effect of this increased amount in the body.

"We've shown that [by using the enzymatic modification of hesperidin] we can get more into the body, but now we are trying to prove the efficacy."

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