Simultaneous extraction and encapsulation of polyphenols from Cajanus cajan leaves and the evaluation of their biological activity

Developing green approaches for the simultaneous extraction and encapsulation of bioactive compounds is crucial in the food fields. In the present study, a one-pot approach to extract and encapsulate polyphenols from Cajanus cajan ( C. cajan ) leaves via 2-Hydroxypropyl- β -cyclodextrin (2-HP- β -CD) was established. The extraction efficiency of 2-HP- β -CD for polyphenols in C. cajan leaves (32.75 mg/g) was higher than that of ethanol (23.42 mg/g). In the release study, the encapsulated polyphenols nanoparticles (PNPs) showed a complete release property (the release rate was 96%). These PNPs had strong activities of scavenging DPPH radicals (IC 50  = 0.52 mg/mL), ·OH radicals (IC 50  = 1.42 mg/mL), and O 2– radicals (IC 50  = 0.30 mg/mL), and had inhibitory effects on gram-positive bacteria ( B. subtilis , S. aureus ) and HepG2 cells (IC 50  = 279.6 μg/mL). Additionally, almost 70% of polyphenols in PNPs were still retained over 15 days in both the gummy candy and beverage. Overall, the proposed method can provide a scientific reference for the manufacture of food and healthful products.