Microwave-assisted processing of ulvans from Mediterranean Caulerpa prolifera with in vitro cell viability

Microwave treatment was selected to extract compounds with gelling and antioxidant properties from Caulerpa prolifera green alga. The proposed microwave hydrothermal conditions had a relevant effect on the antioxidant characteristics of the soluble extracts, achieving the highest values of total phenolic content (80 mg gallic acid/g extract) and antioxidant activities (160 mg Trolox/g extract, 18 mg ascorbic acid/g extract, IC₅₀: 234 μg/mL) at 210 °C and 12 min. The maximum of sulphate and soluble protein contents were identified at 180 °C and 6 min. The highest polysaccharide extraction were found after hydrothermal treatment at 210 °C for 3 min. Time-independent fluids following the power law model were identified for all systems. The viscoelastic values of the proposed gels (elastic modulus, G′, around 500 Pa) improved the G′ values (around 50 Pa) obtained under conventional acid extraction conditions. No water syneresis was observed during one month in cold storage. The ulvan with the highest recovery yields was subjected to in vitro tests in concentrations from 0.25 to 1.0 mg/mL with the fibroblastic cell line 929. The cell viability was confirmed, being of special interest the lowest concentration tested, which promoted a metabolic activity significantly higher (p < 0.05) than the highest ones.