The study, published in The Journal of Nutritional Biochemistry, analyses levels of plasma gamma-tocotrienol in mice after the oral administration of free gamma-tocotrienol or a complex formulation of gamma-cyclodextrin (gamma-CD) and gamma-tocotrienol.
The authors, based at the University of Shizuoka, Japan, said that the results show an improvement of 140 percent in oral bioavailability for the vitamin E form after inclusion with gamma-CD.
“Our results suggest that the in vivo bioactivity of gamma-tocotrienol was improved by an oral administration of a novel tocotrienol rich fraction … with cyclodextrin,” said the authors, led by Noriyuki Miyoshi, from the University of Shizuoka.
“Taken together, our results suggest that the cyclodextrin inclusion improved gamma-tocotrienol bioavailability, resulting in the enhancement of gamma-tocotrienol physiological activity, which would be a useful approach for the nutrition delivery system,” they added.
The authors also suggested that vitamin E inclusion complex with gamma- cyclodextrin may have beneficial effects for several intractable chronic diseases associated with inflammation and oxidative stress.
However, commenting on the new research, Dr. Sharon Ling, Vice President of Scientific Affairs for Carotech Ltd told NutraIngredients that although the study was scientifically interesting, the commercial applications may be limited because the research only concerns gamma-tocotrienols.
“From the commercial point of view, this will have limited application since alpha & delta-tocotrienols have showed promising results for various health indications,” she explained.
The vitamin E family
Tocotrienols are a form of vitamin E that have traditionally been in the shadow of the more popular vitamin E form – tocopherols.
Overall, there are eight forms of vitamin E: four tocopherols (alpha, beta, gamma, delta) and four tocotrienols (alpha, beta, gamma, delta).
The possible beneficial effects of vitamin E supplementation have been studied with regard to many diseases, including atherosclerosis, other cardiovascular diseases, certain types of cancer and a number of neurodegenerative diseases.
Tocotrienols have slightly higher antioxidant activity than tocopherols in membranes and possess neuroprotective, anticancer and cholesterol-lowering properties that are often not exhibited by tocopherols, noted the authors.
The authors said that cyclodextrin (CD) is widely used to form an inclusion complex with bioactive compounds to improve their solubility, stability and diffusibility.
Among the three natural cyclodextrins, they said that gamma-CD shows the highest water solubility and is the only form that is easily digested.
Therefore, much attention has recently been given to the usage of gamma-CD as a ‘host’ molecule in oral bioavailability experiments and as a promising nutrition delivery system.
The new study examined the effect of gamma-tocotrienol inclusion with gamma-CD on its bioavailability.
In the study, the Japanese researchers compared the bioavailability of gamma-tocotrienol when given as a tocotrienol rich fraction (TRF) as a free oil, and as an inclusion complex with cyclodextrin (CD). The TRF (Oryza tocotrienol 72), gamma-CD and TRF/CD complex were provided by Oryza Oil & Fat Chemical Company (Aichi, Japan) and Cyclochem (Kobe, Japan).
The bioavailability values for plasma gamma-tocotrienol levels reported to be markedly greater (a 1.4-fold increase) in mice administered TRF/CD orally than those given free TRF alone. Whilst Miyoshi and colleagues observed the half-life of gamma-tocotrienol in the plasma of mice given TRF/CD was 1.8-fold higher than that of the free TRF.
Dr Ling, of Carotech told NutraIngredients that the increase of 140 percent in bioavailability shown in mice in the current study leaves very little commercial application as there are already products available on the market that show increases in bioavailability of up to 250 percent in humans.
Ling also added that Carotech’s collaborators at the University of Science Malaysia previously investigated using cyclodextrins to prepare a powder form of Tocomin (Carotech Ltd’s palm tocotrienol complex) in the early years, but abandoned the project “due to several limitations of the compound/formula.”
She added that because cycloextrin is the form of a powder it has limited capacity for encapsulation and is not suitable for use in soft gels and other dosage forms.
Source: The Journal of Nutritional Biochemistry
Published online ahead of print, doi: 10.1016/j.jnutbio.2010.09.011
“The enhancement of the oral bioavailability of γ-tocotrienol in mice by γ-cyclodextrin inclusion”
Authors: N. Miyoshi, Y. Wakao, S. Tomono, M. Tatemichi, T. Yano, H. Ohshima