Enhanced extraction of antioxidant compounds from propolis using non-thermal plasma pretreatment and ultrasonic-assisted methods

This study investigated the combined effects of non-thermal plasma (NTP) pretreatment and ultrasound-assisted extraction (UAE) on improving the recovery of antioxidant compounds from Brazilian and stingless bee propolis. Plasma conditions were first optimized using stingless bee propolis. Argon plasma treatment for 15 min followed by UAE at 50 °C for 2 h yielded the highest total phenolic content (TPC, 3.69 ± 0.1 mg GAE/g) and total flavonoid content (TFC, 1.48 ± 0.05 mg QUE/g). Air plasma treatment for 5 min increased TPC and TFC by 11.15% and 37.39%, respectively. Extending UAE to 4 h further enhanced phenolic and flavonoid recovery. Under optimized conditions (air plasma for 5 min or argon plasma for 15 min combined with UAE at 50 °C for 4 h), Brazilian propolis showed greater enhancement following air plasma treatment (TPC +54.62%; TFC +61.39%), whereas argon plasma was more effective for stingless bee propolis (TPC +19.56%; TFC +26.72%). Improved extraction was attributed to plasma-induced modification of the resin matrix. Antioxidant activity increased, as shown by lower DPPH IC 50 values, whereas antibacterial activity against Paenibacillus larvae and Staphylococcus aureus remained unchanged. Overall, NTP–UAE represents a promising green approach to improve the antioxidant functionality of propolis.