Optimization of ultrasound-assisted extraction of flavonoids from Portulaca oleracea L., the extraction kinetics and bioactivity of the extract

In this study, a response surface methodology was employed to optimize the extraction conditions for total flavonoids (TF) from Portulaca oleracea. The screening of significant factors was conducted using the Plackett-Burman design, followed by further optimization using the Box–Behnken design. The optimized extraction conditions yielded a TF content of 21.64 ± 0.35 mg rutin equivalents/g. The phenomenological model indicated that the use of ultrasound assistance improved the extraction efficiency by accelerating the dissolution process of TF. The flavonoid extracts from P. oleracea exhibited activity against Cutibacterium acnes, with a minimum inhibitory concentration of 0.39 mg/mL and a minimum bactericidal concentration of 0.78 mg/mL. Moreover, these extracts demonstrated DPPH free radical scavenging activity, with an IC₅₀ value of 0.019 mg/mL. Notably, the extracts obtained through ultrasound-assisted extraction exhibited higher total flavonoid content, antibacterial activity, and antioxidant activity compared to those obtained through conventional solvent extraction. The analysis of the P. oleracea flavonoid extract identified rutin, quercetin, kaempferol, isorhamnetin, apigenin, and luteolin as the main flavonoid components. These findings highlight the validity of ultrasound-assisted extraction as a reliable method for obtaining flavonoids from P. oleracea and underscore the potential of P. oleracea for application in the cosmetic industry.