A microwave-based technique to determine saccharides and polyols contents in Spirulina (Arthrospira platensis)

Abstract

The growing demand for Spirulina (Arthrospira platensis) as a dietary supplement suggests that a rapid and reliable method to determine its saccharides and polyols content would be of great interest. Additionally, the impact of these microalga growing conditions may have on such content would be really useful for Spirulina producers. This manuscript presents the development and validation of a new analytical microwave-assisted extraction (MAE) method as the first step in determining saccharides and polyols in spirulina samples. A Box Behnken design has been employed to evaluate three extraction variables, viz., temperature (x1: 30, 55 and 80 °C), solvent composition (x2: 0, 25, and 50% ethanol in water), and solvent to sample ratio (x3: 10:1, 20:1, and 30:1 mL of solvent per g of sample). These extraction variables have been optimized by Response Surface Methodology (RSM). Under the optimal conditions that have been thereby established (i.e., 30 °C, 50% ethanol in water, and 30:1 solvent to sample ratio), a kinetic study has been performed with full recovery in 15 min. Subsequently, the developed MAE method was validated by determining the number of parameters, including linearity, LODs, LOQs, accuracy, and precision. Finally, the resulting MAE method was successfully applied to determine saccharides and polyols contents in a number of Spirulina samples that had been cultivated in varying salinity media. Five saccharides and polyols were identified in Spirulina, i.e., inositol, glycerol, sorbitol, glucose, and maltose. The total amount of the compounds of interest in the Spirulina that had been cultivated in a higher salinity media (17 and 25 g L−1 of sodium chloride in water) was six-folds higher than the one cultivated in low saline water (0 and 3 g L−1 of sodium chloride in water). This substantial content difference was mainly explained by the considerable increment in glycerol and glucose contents when grown in a more saline medium. Therefore, it has been demonstrated that the new method is suitable to determine saccharides and polyols contents in different Spirulina samples.