Carotenoids from the extreme halophilic archaeon Haloterrigena turkmenica: identification and antioxidant activity

Haloterrigena turkmenica was able to synthesizecarotenoids when grown in halobacteria medium. Thesemolecules have antioxidant properties and find application infood, cosmetic, and pharmaceutical fields. The carotenoidswere extracted with methanol, separated by RP-HPLC, andidentified by mass spectrometry and UV/Vis spectra analyses.The C50carotenoids were the main pigments, and C30,C40,and C51carotenoids were also detected. Seven geometricisomers were distinguished for bacterioruberin, monoanhydrobacterioruberin,and bisanhydrobacterioruberin. Theassignment to a specific isomer was tentatively attemptedthrough the analysis of the corresponding UV/Vis spectrum,the intensity of the cis peak, and its spectral fine structure.Lycopene, phytoene, and lycopersene were among the minorcarotenoids further identified. The extract displayed antioxidantpower higher than alpha-tocopherol, butylhydroxytoluene,and ascorbic acid used as reference compounds.Our studies identified for the first time seven geometric isomersof bacterioruberin derivatives and 30 carotenoids in ahaloarchaeon.