Phytochemical Composition and Bioactivity of Different Fruit Parts of Opuntia robusta and Opuntia ficus-indica: Conventional Versus NADES-Based Extraction

Could a green solvent outperform traditional methanol in unlocking the hidden powers of cactus fruit? A new study reveals that a simple glycerol-urea mixture matches methanol's extraction might—and even uncovers a first-ever enzyme-blocking secret in one species.

Cactus fruits are more than just spiky snacks. Scientists have long known their peels and seeds are packed with bioactive compounds, but the best way to extract these treasures has been up for debate. This study pitted two Natural Deep Eutectic Solvents (NADESs)—glycerol–urea and citric acid–sorbitol—against a conventional 50% methanol solution, using fruit parts from Opuntia robusta and Opuntia ficus-indica.

The results were surprising. Glycerol–urea performed as well as methanol in pulling out phenolic compounds with strong antioxidant activity. Peel extracts stood out, boasting the highest levels of bioactive molecules, including phenolic acids at 525.49 µg/gDW in O. robusta and 362.96 µg/gDW in O. ficus-indica. These extracts also inhibited a panel of enzymes—acetylcholinesterase, butyrylcholinesterase, tyrosinase, α-glucosidase, and α-amylase—though the strength varied by species and fruit part.

A standout moment: this is the first evidence of tyrosinase inhibitory activity in O. robusta, with the strongest effect seen. Such enzyme inhibition hints at potential applications in managing conditions like Alzheimer's, diabetes, or skin hyperpigmentation. The study underscores that cactus fruit waste, especially peels, could be transformed into nutraceuticals, while NADESs offer a sustainable extraction medium that doesn't compromise on efficacy.

Key Points

• Glycerol–urea NADES matched methanol's phenolic extraction efficiency.
• Peel extracts had highest bioactives, with phenolic acids up to 525.49 µg/gDW.
• First evidence of tyrosinase inhibition in Opuntia robusta.