Optimization of Ultrasound-Assisted Extraction of Antioxidants From Rabbi Date Seed and Identification of Fatty Acid and Phenolic Compound Profiles of the Seed Extracts

Abstract

Date seed, a major byproduct of date processing, contains valuable phytochemicals. This study optimized ultrasound-assisted extraction (UAE) conditions for phenolic and antioxidant compounds from Rabbi date seed using response surface methodology (RSM) and the Box–Behnken design. The independent variables included the UAE time (15, 30, and 45 min), temperature (35°C, 50°C, and 65°C), and solvent (ethanol or methanol) concentration (30%, 50%, and 70%). The optimal conditions of the UAE of the phenolic and antioxidant compounds were found to be the time of 44.99 min, the temperature of 64.99°C, and the solvent concentration of 70%, resulting in a total phenolic content (TPC) of 264.60 mg GAE/g dry matter and a half maximal inhibitory concentration (IC50) of 4.64 μg/mL for the optimum ethanolic extract and a TPC of 329.19 mg GAE/g dry matter and an IC50 of 4.26 μg/mL for the optimum methanolic extract. RP-HPLC analysis identified cinnamic and chlorogenic acids as the dominant phenolics, while GC-FID revealed oleic and lauric acids as major fatty acids (FAs). Methanolic extracts had more phenolic compounds and antioxidant activity than ethanolic extracts. These results highlight the potential of date seed oil and extracts in food fortification and nutraceutical applications, suggesting further exploration in nanofood formulations.