Effect of Environmentally Friendly Betalain Extraction Methods on Antioxidant Compounds of Tunisian Opuntia stricta Fruit

This study focuses on the extraction of betalain compounds from <i>Opuntia stricta</i> as a natural alternative to synthetic colorants and sustainable environmentally friendly technology solutions. Non-conventional extraction technologies including microwave (MW) and ultrasound (US) were used alone or in combination. The extraction process was conducted for both undried <i>Opuntia stricta</i> (OS) and dried <i>Opuntia stricta</i> (DOS) plant material at two distinct drying temperatures, 40 °C and 60 °C, to assess the stability of betalain molecules. The colorant's potential was evaluated by determining the betalain content, total phenolic content, and antioxidant activity. The MW (2 min) and MW (2 min) + US (10 min) extraction processes yielded the greatest betalain content in OS fresh weight (FW), with 48.54 ± 0.29 mg/100 g FW and 51.01 ± 0.16 mg/100 g FW, respectively. Furthermore, the results showed a considerable drop in betalain content when the plant material was dried at 40 °C and 60 °C, with reduction rates of 53.75% and 24.82%, respectively, compared to the betalain content before the drying process. The LC-DAD-ESI-MS analysis supported this result, revealing the presence of 17-decarboxy betanin, 17-decarboxy neobetanin, and Cyclo-dopa5-O-βglucoside in DOS at 40 °C. This study highlights the potential future in the sustainable green extraction of betalain compounds with less heat degradation to offer a stable natural colorant.