|Fucoxanthin is an epoxy carotenoid with important beneficial bioactivities. In this
study, a type of microalgae (diatom) Thalassiosira weissflogii was used as the feedstock for
fucoxanthin extraction. Effects of solvent types, feedstock conditions, presence of
antioxidants, and extraction time on fucoxanthin yield were investigated. Results suggested
diatoms might be a more cost effective source for fucoxanthin extraction than brown algae.
Wet diatoms can achieve high extraction yields over a much shorter period. Yield was 100.7
± 5.8% of the average total available fucoxanthin in the diatoms after 10 min of extraction
with acetone. Adding 0.3% of the antioxidant, butylated hydroxyanisole (BHA), during
extraction may not increase the yields significantly in the short time, but it could prevent
the further potential decomposition of fucoxanthin.
Several studies have suggested that fucoxanthin has anti‐obesity, anti‐diabetic, and
anti‐cancer properties. We sought to determine whether fucoxanthin, gavaged daily, would
demonstrate anti‐obesity and anti‐diabetic properties in rats fed a high‐fat/high‐sucrose
diet. To accomplish this, we performed an energy balance study in three groups of Wistar
rats. Two groups of rats were fed a high‐fat/high‐sucrose diet. One of these groups was
gavaged daily with fucoxanthin, while the other group was gavaged with vehicle. The
remaining group was fed a low‐fat diet and was gavaged daily with vehicle. Food intakes
and body weights were determined daily for approximately 12 weeks. After 10‐11 weeks on
the respective diets, a subset of rats from each group was placed in metabolic cages for 3
days to determine energy expenditure, RQ, and physical activity. Lastly, all rats were given
an oral glucose tolerance test to determine how the diets and fucoxanthin treatment
affected insulin sensitivity.
Results obtained in this study were contrary to the hypothesis that fucoxanthin has
anti‐obesity and anti‐diabetic properties. In fact, we found that fucoxanthin‐treated rats
fed a high‐fat/high‐sucrose diet gained significantly more body fat than vehicle‐treated rats
fed the same diet. The increase in body fat associated with fucoxanthin treatment did not
appear to be related to a change in the energy expenditure. Rather, the increase in body fat
appeared to be due to a non‐statistically significant increase in food intake and an increase
in the energetic efficiency of the calories that were consumed. In addition, fucoxanthintreated
rats fed the high‐fat diet also showed greater insulin resistance as compared to the
vehicle‐treated rats fed the high fat diet. No difference in insulin resistance was found
between low‐fat‐fed and high‐fat‐fed rats treated with vehicle. The greater insulin
resistance of fucoxanthin‐treated rats may reflect greater amounts of overall fat gain or
perhaps a greater amount of fat deposition in nonadipocytes tissues.
The present study suggests that caution should be exercised when considering
whether fucoxanthin has anti‐obesity and anti‐diabetic bioactivities. The specific
experimental conditions under which fucoxanthin is extracted and tested may greatly affect
the outcome of such studies.