Optimization of NADES-based green extraction of ellagitannins from rambutan peel with enhanced antioxidant activity.

Rambutan (Nephelium lappaceum L.) peel contains bioactive compounds such as geraniin, corilagin, ellagic acid, and gallic acid, known for their antioxidant, anti-inflammatory, and anticancer properties. Traditional extraction methods involve toxic solvents like methanol and ethanol, posing environmental and safety concerns. This study optimized the extraction of ellagitannins from rambutan peel using Natural Deep Eutectic Solvents (NADES), which are sustainable, non-toxic, and cost-effective. The optimal conditions-water content (20 %), temperature (80 °C), and time (60 min)-were identified using Response Surface Methodology (RSM). The NADES system, composed of betaine (hydrogen bond acceptor) and 1,2-propanediol (donor) in a 1:2 M ratio, achieved the highest ellagitannin yield (54.29 μg/mg) and antioxidant activity (DPPH IC50 = 35.86 μg/mL, ABTS IC50 = 37.66 μg/mL). These findings demonstrate that NADES can be effectively tailored for bioactive compound extraction from rambutan peel, providing a greener alternative for the food, pharmaceutical, and cosmetic industries.