Emulsions may boost flavonoid bioavailability, suggests study

Emulsions may boost flavonoid bioavailability, suggests study

By Nathan Gray, 21-Feb-2011

Related topics: Research, Phytochemicals, plant extracts

The use of flavonoids as stabilisers for oil-and-water emulsions could boost the bioavailability of the compounds, according to new research.

The study, published in the Journal of Agriculture and Food Chemistry, shows that common food flavonoids may act as “excellent stabilizers” of oil-in-water emulsions, and suggests that role of ‘stabilizer’ in an emulsion may increase the bioavailability of such compounds by delivering them to the gut without the need for more complex techniques such as encapsulation.

Researchers from the University of Leeds, explained that the compounds stabilise the emulsions due to “a tendency for accumulation at the Oil−Water interface” which in some cases “can provide very good stabilization of oil-in-water (O/W) emulsions.”

“Understanding of the physicochemical properties of flavonoids is probably the first step in trying to rationalize their bioavailability,” said the authors, led by Brent Murray, Professor of Food Colloids at the University of Leeds.

They added that the results of the study “may be highly significant with respect to the delivery of such insoluble compounds to the gut, as well as their digestion and absorption.”

Flavonoid benefits

Flavonoids are a group of polyphenol plant metabolites that have generated considerable interest in recent years due to their association between dietary consumption and health benefits.

The compounds have been suggested to have many healthy benefits, the evidence for which has come mainly from studies of their in vitro activity as antioxidant and anti-inflammatory agent, in addition to some in vivo animal studies.

But, according to the authors, “in order to fully understand the in vivo consequences of dietary flavonoid ingestion and to make sense of in vitro and animal studies, the processes of flavonoid absorption and metabolism need to be better understood.”

Prof. Murray and his colleagues said despite the occurrence of a considerable amount of flavonoids in the daily diet, flavonoids are generally known to have poor solubility in water.

According to the authors this has spurred “a large number of studies to try and encapsulate them with various structures that might aid their dispersibility, using similar strategies as for water-insoluble drugs.”

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However, they said that by exploring the hydrophobic/hydrophilic nature of flavonoids, it may be possible to find solutions to the problem of solubility by using an emulsion.

Study details

The authors screened a wide range of flavonoids for their emulsification behaviour, noting that it is difficult to predict how good an emulsifier the flavonoid will be, based on the molecular structure of individual flavonoids.

The authors found that some common food flavonoids (including K7Neo, Q3R (rutin), N7Neo(naringin), N7R, and tiliroside) act as excellent stabilizers of oil-in-water emulsions, through their adsorption (as water-insoluble particles) to the surface of the oil droplets – forming a ‘coating’ around a large droplet, known as a Pickering emulsion.

Murray and co- workers said that the Picketing emulsion droplets formed by flavonoids in an oil/water emulsion are “a huge energy barrier to droplet shrinkage or coalescence, and the emulsions are very stable.”

Rutin and naringin were found to produce the finest emulsions, with droplet sizes of 6, and 5 micrometers (μm), respectively.

Healthy emulsion

The researchers said the results may have significance with respect to the location of flavonoid compounds in real food systems, explaining that flavonoids may be delivered as part of a stable oil−water interface which occurs in foods containing emulsified oil.

As such, they added that the study holds promise for the transport and delivery of flavonoids, which are generally insoluble, to the gut without the use of more complex, and often expensive techniques such as encapsulation.

The results may also have an impact on the understanding of human digestion and absorption of flavonoids, said Murray and colleagues.

Source: Journal of Agriculture and Food Chemistry
Published online ahead of print, doi: 10.1021/jf1041855
“Particle-Stabilizing Effects of Flavonoids at the Oil−Water Interface”
Authors: Z. Luo, B.S. Murray, A. Yusoff, M.R. A. Morgan, M.J. W. Povey, A.J. Day

Ginseng extract may offer brain protection: Study

Ginseng extract may offer brain protection: Study

By Nathan Gray, 13-Jan-2011

Related topics: Research, Cognitive and mental function

An active protein found in ginseng root shows signs of neuroprotective support against stroke, and may benefit other neurodegenerative diseases, according to new research.

Published in the Journal of Ethnopharmacology, the study assessed the effects of Ginsenoside Rb1 (GRb1) – an active protein component of the ginseng root – on a group of adult male rats one with ischemic stroke.

The research found that GRb1 significantly increased the number of neural stem cells – known as neural precursors cells – after ischemic stroke compared to rats not infused with GRb1.

“The present study demonstrates that GRb1 promotes the neural behavior recovery, […] and induces neurogenesis after cerebral ischemia,” said the researchers, led by Dr Qiong-Lan Yuan from Tongji University School of Medicine in China.

“These results provide new support for the neuroprotective effects of GRb1 against ischemic stroke, which may be potential therapeutic treatment for other neurodegenerative disease such as Alzheimer disease and Parkinson disease,” they added.


Ginseng (Panax quinquefolius), has been an important component of Chinese medicine for thousands of years, and is suggested to protect the brain from the effects of certain types of stroke.

Previous research has suggested that an the ginseng active component Ginsenoside Rb1(GRb1) has neuroprotective effects or for cerebral ischemia.

It has been suggested that there beneficial properties are due to their effects on brain-derived neurotrophic factor (BDNF) – a protein that helps to support the survival of existing neurons, and encourages the growth and differentiation of new neurons and in the brain. Whilst other studies have linked levels of caspase- 3 – a protein that plays a vital role in programmed cell death and has been shown to be elevated levels after certain cardiovascular events.

“Recently, a battery of studies has shown that BDNF is strongly involved in neurological recovery after cerebral ischemia,” said the researchers.

However, Dr Yuan and colleagues said that the underlying mechanism of this protective function is unclear.

“We assessed whether this neuroprotective effect of GRb1 was mediated by the levels of brain-derived neurotrophic factor (BDNF), by the levels of caspase-3 proteins, and by induced neurogenesis in rats following transient cerebral ischemia,” said the authors.

Study details

The mechanism of GRb1 neuroprotection was evaluated by observing expressions of BDNF and caspase-3 and neurogenesis in rats with experimental cerebral ischemia.

Results revealed the GRb1 infusion after cerebral ischemia significantly promoted recoveries of neurological functions at three and five days post-stroke compared to ischemic rats not infused with GRb1.

They reported that BDNF levels were significantly increased in GRb1-treated rats, whilst infusion with GRb1 post- stroke was shown to significantly reduce levels of caspase-3 compared to control rats.


Yuan and colleagues said that the findings of the study indicate that regulation of the expressions of BDNF and caspase-3 may be involved in GRb1-induced neuroprotection against cerebral ischemia.

GRb1 infusion after cerebral ischemia significantly inhibited caspase-3 activity at different time points. This is, to our knowledge, the first report that GRb1 inhibits caspase-3 in cerebral ischemia,” said the researchers.

“It is [also] the first time to show that GRb1 is capable of increasing BDNF expression after stroke … The increased BDNF expression may explain partly the neurological functional recovery after cerebral ischemia with GRb1 treatment,” they added.

However they added that the underlying mechanism by which GRb1 promotes functional recovery after stroke is still not completely clear.

Next questions

“Perhaps the most important questions in next study are to assess whether neural precursors cells differentiate into neurons with appropriate regional specificity after cerebral ischemia,” said Yuan and co- workers.

They explained that if the new neurons are capable of long-term survival and integration, then GRb1-induced neurogenesis is a plausible strategy for many other neurodegenerative disorders besides cerebral ischemia.

Source: Journal of Ethnopharmacology
Volume 132, Issue 2, Pages 393-39, doi: 10.1016/j.jep.2010.07.033
“Ginsenoside Rb1 regulates the expressions of brain-derived neurotrophic factor and caspase-3 and induces neurogenesis in rats with experimental cerebral ischemia”
Authors: X.Q. Gao, C.X. Yang, G.J. Chen, G.Y. Wang, B. Chen, S.K. Tan, J. Liu, Q.L. Yuan