Optimization of extraction procedure and antioxidant activity of C50 carotenoids from Halorubrum sp. HRM-150

C50 carotenoids are promising bioactive compounds produced by halophilic archaea. Relevant studies have focused on their outstanding antioxidant activity, whereas the extraction process has received less attention. In this study, the effect of factors on carotenoid extraction efficiency was explored through single-factor and orthogonal experiments. The results showed that the C50 carotenoids were effectively extracted by suspending and homogenizing cell pellets in methanol (1:30, w-v) for 10 min, subsequently incubating at 30 °C for 30 min in the dark, finally centrifuging and drying over vacuum rotary evaporation at 30 °C in the dark. The carotenoid content increased 1.84 times by the above procedure than that before optimization. Moreover, the UVVis spectra, TLC and HPLCMS analysis revealed that the main component of carotenoids extracted from Halorubrum sp. HRM-150 was bacterioruberin (84.12 %), followed by monoanhydrobacterioruberin (15.13 %). Both carotenoid extract and bacterioruberin exhibited antioxidant capacity, which were significantly higher than that of astaxanthin (p < 0.05) by scavenging assays of 2,2-azinobis-3-ethyl-benzothiazole-6-sulfonic acid, 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radicals. In addition, the hydroxyl radical scavenging rate of bacterioruberin was significantly higher than that of carotenoid extract (p < 0.01), indicating its potential activity against or delaying diseases caused by reactive oxygen species. C50 carotenoids (especially BR) have great application prospects in human health due to their excellent antioxidant capacity.