Effects of Binary Solvent System on Radical Scavenging Activity and Recovery of Verbascoside from Lemon verbena Leaves

Verbascoside is the major biophenolic compound of Lemon verbena leaf. This study aimed to investigate the effects of the binary solvent system on the free radical scavenging activity (FRSA) and verbascoside recovery from L. verbena leaves, as well as the kinetic mass transfer of verbascoside.

Classic extraction was performed using various ratios of ethanol (EtOH) and water (H2O) (50:50-90:10% v/v). The FRSA was analyzed using spectrophotometric methods (2,2-diphenyl-1-picrylhydrazyl [DPPH] and hydroxyl radical [HO˙] assays). Reversed-phase high-performance liquid chromatography was used for the qualification and quantification of verbascoside, and the Peleg model described the kinetic mass transfer of verbascoside.

The hydroethanolic solvent was composed of EtOH:H2O (80:20% v/v) as the optimal medium for the maximum recovery of verbascoside (19.20 ± 0.12 mg/g) and FRSA of the extracts (45.25 ± 0.95% DPPHsc% and 31.17 ± 1.20% HOsc%). The Peleg model had a proper fit for the observed data with the highest coefficient of determination (R2 =0.999), the lowest root mean square error (RMSE = 0.093), and the mean relative percentage deviation modulus (E = 0.968).

The valuable bioactive compounds of L. verbena could be successfully extracted using the binary solvent system. The Peleg model is also an efficient non-linear model to describe the verbascoside release rate during extraction.