Optimization of extraction process for phenolics and antioxidants from edible algae Ulva fasciata using response surface methodology and its nutritional composition

Seaweeds are a rich source of biomolecules with outstanding biological effects. Ulva fasciata is an abundant natural resource in India that could be used to produce functional foods. However, the sustainable and cost-effective valorization of these resources requires an optimized process for extracting bioactives. Ultrasound-assisted extraction (UAE) offers a balanced set of advantages and disadvantages. This study aimed to optimize the most common extraction parameters, such as solvent concentration, time and solid-to-solvent ratio, using UAE to maximize the recovery of total phenolics (TPC) and antioxidants from U. fasciata , using response surface methodology (RSM), and to address the nutritional composition. Carbohydrates were found as the most abundant macronutrients (61.73 g/100 g), followed by crude lipids (15.97 g/100 g) and proteins (11.76 g/100 g) on a dry weight basis, providing 438.03 Kcal/100 g of energy. Palmitic and oleic acids were the most abundant fatty acids, and a varied mineral composition was also stated. RSM-BBD experiment, used to extract the maximum quantity of TPC and antioxidants in the shortest possible time using the least amount of the source, achieved that with 17 runs at a solvent concentration of 40 %, 5 min of sonication and a solid-to-solvent ratio of 74.99 mg/mL. Interaction effects were explained using second-order polynomial equations and presented as contour and 3D graphs, and the significance of the model was confirmed by ANOVA, regression and lack-of-fit tests. The observed response values were lower than in previous reports and were attributed to differences in processing techniques and storage conditions used, possible degradation of sensitive compounds, and natural variability related to the geographic origin. These findings underline that U. fasciata could be useful for future economic-level extractions, saving time on experiments and valorizing this natural resource as a feed and food ingredient, while promoting environmental sustainability. • Marine-derived bioactives have a plethora of pharmacological attributes. • Sustainable bioprospecting of seaweeds is gaining increasing attention. • Recovery of total phenolics and antioxidant capacity of Ulva fasciata was optimized. • Data obtained underline the potential nutraceutical and nutritional value of U. fasciata as a food and feed source.