Optimised extraction of β ‐carotene from Spirulina platensis and hypoglycaemic effect in streptozotocin‐induced diabetic mice

BACKGROUND Spirulina platensis is rich in β ‐carotene, which possesses many important biological activities. This study investigated the ultrasound‐assisted extraction and purification of β ‐carotene from Spirulina platensis by using response surface methodology ( RSM ), determined its antioxidant capacity in vitro and explored its hypoglycaemic effect in diabetic mice. RESULTS The raw β ‐carotene extract with a concentration of 1942.14 ± 10.03 µg mL −1 was obtained at the optimised condition by RSM (0.40 of the solid–liquid ratio, 51% of the extraction power, and 17 min of the extraction time), and the purity of evaporated β ‐carotene extract reached 816.32 ± 10.57 mg g −1 after purified by a NKA ‐9 resin with a sampling and elution rate of 1 mL min −1 . The β ‐carotene extract scavenged 1,1‐diphenyl‐2‐picrylhydrazyl and hydroxyl free radicals with the highest ratios of 44 ± 0.26% and 35 ± 0.45% respectively, and exhibited strong inhibiting capacity on anti‐lipid peroxidation. The blood glucose level of streptozotocin‐induced diabetic mice was significantly reduced from 15.81 ± 1.71 mmol L −1 to 8.10 ± 0.88 mmol L −1 after 10 d administration of the β ‐carotene extract [100 mg kg −1 body weight ( BW )], and the increased food and water intakes in the diabetic mice were also significantly relieved after β ‐carotene treatment. CONCLUSION Our results suggested that extraction of β ‐carotene from Spirulina platensis had potential prospects in scaled‐up industrialisation and healthcare applications. © 2015 Society of Chemical Industry