Ultrasonic-Assisted Extraction of Phenolic Compound From Harumanis Mango Leaves (Mangifera indica) Using Green Natural Deep Eutectic Solvents (NADESs)

What if the secret to greener chemistry is hiding in a mango leaf? Scientists just found a way to pull powerful antioxidants from Harumanis mango leaves using solvents that are as eco-friendly as they are effective.

Harumanis mangoes are a pride of Perlis, Malaysia, but their leaves are often overlooked. Now, researchers are giving these leaves a second life by extracting phenolic compounds—natural antioxidants—using a new class of green solvents called Natural Deep Eutectic Solvents, or NADES. These solvents are made by simply heating and stirring natural ingredients like organic acids and glycerol until they form a clear liquid, offering a biodegradable alternative to harsh conventional solvents.

In this study, five different NADES systems were tested against traditional solvents like ethanol and methanol. The results were striking: a lactic acid:glycerol mixture outperformed all others, yielding 135.74 mg of phenolic content per gram of dried leaf. When combined with ultrasonic-assisted extraction, that number jumped to 142.87 mg—beating the best conventional solvent, 50% ethanol, which reached 133.09 mg. The least effective NADES, sodium acetate:glycerol, still managed 32.76 mg, showing that even the weakest green option holds promise.

The winning extract was packed with phytochemicals—saponins, phenols, glycosides, and tannins—and showed antimicrobial activity against both gram-positive and gram-negative bacteria. This suggests that Harumanis leaves, when processed with NADES, could become a source of therapeutic agents. The study opens the door to a cleaner, more sustainable way to tap into nature's pharmacy, one mango leaf at a time.

Key Points

• NADES outperformed conventional solvents for phenolic extraction
• UAE with lactic acid:glycerol yielded highest TPC at 142.87 mg GAE/g
• Extract showed antimicrobial activity against gram-positive and gram-negative bacteria