Studies on Extraction of Fucoxanthin and Its Potential Anti‐obesity Effect
Type of Degreedissertation
Nutrition and Food Science
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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 iii 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.