Determination of astaxanthin in crayfish and its by-products by Ultra High Pressure Liquid Chromatography

Introduction: The red crayfish Procambarus clarkii is native to the south-central USA and north-eastern Mexico, but nowadays it can be found worldwide [1]. This species is predisposed to spread and to become invasive due to several life-history traits (early maturity, rapid growth, large number of offspring, and plastic life cycle) as well as biological features (tolerance to extreme environments, dispersal, polyphagy, predatory and competitive ability, and behavioral flexibility) [2]. P. clarkii can damage agricultural fields, such as rice fields, by the burrowing activity which affects the control of the water flow, can interfere with herbicides application and cause damages in the small levees [3]. To contradict this, it is important to study its composition, namely in bioactive compounds with potential human health benefits to find possible profit applications, namely for the food, cosmetics and pharmaceutical industries. The aim of the present work was to determine the astaxanthin content of P. Clarkii by ultra high pressure liquid chromatography (UHPLC) with diode array detection (DAD). Material and Methods: Besides the whole crayfish, head, exoskeleton and meat have also been analysed, before and after boiling. Samples (0.25g) were extracted with 5 mL of methanol. The chromatographic separation was achieved using a vanguard pre-column (UPLCÒ BEH, 1.7 µm particle size) and a column (UPLCÒ BEH, 2.1 x 50 mm, 1.7 µm particle size) at 20 °C. Astaxanthin detection was monitored at 480 nm. The mobile phase is a gradient of mobile phase A [dichoromethane/methanol with ammonium acetate/acetonitrile 5:20:75 (v/v)] and mobile phase B (ultrapure water) with a flow rate of 0.5 mL/min. A volume of 10 µL was injected into the UHPLC. Results and Discussion: The method used to determine the astaxanthin is simple and allows good resolution at low detection levels. In both types of samples (raw and cooked crayfish), the exoskeleton had the highest concentration of astaxanthin, followed by the head and then, by far, by the crayfish meat. The cooked exoskeleton samples showed a more intense red coloration (28.4 ± 2.5 µg astaxanthin/g), caused by the release of astaxanthin from the carotenoproteins by denaturation due to increased temperature [4]. Conclusion: Crayfish by-products can be considered a good source of astaxanthin, which is a potent antioxidant with a variety of applications in food technology and nutrition (e.g. pigmentation of salmon and trout bred under aquaculture).