Chlorophylls and their derivatives are currently used in a wide range of applications. To replace the volatile organic solvents commonly applied for their extraction from biomass, aqueous solutions of non-ionic surfactants are studied herein in the extraction of chlorophylls from spinach leaves. Aqueous solutions of several surfactants were screened, demonstrating that their hydrophilic-lipophilic balance (HLB) plays the pivotal role on the extraction performance, with the best results obtained for surfactants with a HLB ranging between 10 and 13. A response surface methodology (RSM) was then used to optimize operational conditions (surfactant concentration, solid-liquid ratio and temperature), leading to a maximum extraction yield of chlorophylls of 0.94 mg/g. After the extraction step, the chlorophylls-rich extract was concentrated by heating above the surfactant-water cloud point, leading to the separation into two-phases, and to a concentration factor of 9 and a recovery of 97% of chlorophylls in the surfactant-rich phase. The antioxidant activity of the extracts was finally appraised, showing that the antioxidant activity of the aqueous chlorophylls-rich extracts is higher than that obtained with volatile organic solvents. The obtained results show the potential of aqueous solutions of non-ionic surfactants to extract highly hydrophobic compounds from biomass and their possible direct use in cosmetic and nutraceutical applications, without requiring an additional recovery or purification step.
Keywords: Solid-liquid extraction; antioxidant activity; aqueous solutions; concentration; non-ionic surfactants; spinach leaves, chlorophylls.