Designing a sustainable extraction platform using deep eutectic solvents: Valorization of sidr leaves into bioactive-rich fractions

Sidr (Ziziphus spina-christi L.) leaves are a potential source of phenolic bioactives exhibiting promising an tioxidant properties. A sustainable extraction system based on deep eutectic solvents (DESs) was developed for the recovery of bioactive-rich extract from Sidr leaves in the present study. Methods: Six DES systems prepared from glycerol with lactic acid or propionic acid were screened. Fourier transform infrared (FTIR) spectroscopy confirmed DES formation through shifts and broadening of characteristic bands associated with hydrogen bonding interactions. Glycerol:propionic acid (1:1) was selected as the most effective solvent by principal component analysis (PCA). Extraction parameters were optimized by Box- Behnken design using immersion time, water addition and sample mass as variables. Results: Total phenolic content (TPC) were between 10.10 mg-GAE/g-DM and 61.23 mg-GAE/g-DM, while rutin content varied from 4.69 mg/g to 32.50 mg/g. Water addition was the most influential factor for phenolic recovery. The optimized conditions were 30 min, 30% water addition and 0.948 g sample mass. Antioxidant activity correlated with TPC and total flavonoid content (TFC). Conclusion: Antioxidant capacity of the Sidr leaf extract is mostly contributed by phenolic matrix rather than an individual compound.