Comparison of extraction methods for the assessment of total polyphenol content and in vitro antioxidant capacity of horsemint (Mentha longifolia (L.) L.)

Horsemint (Mentha longifolia (L.) L.) is a less studied, wild-growing species. Aim of the experiments was to define effective extraction method providing highest antioxidant capacity and polyphenol content from the plant, for long-term goal of food preservation uses. We applied Soxhlet and ultrasonic (US) extraction, both with methanol (MeOH) and ethanol: water in 7:3 (WA) as solvents. Thirty-six accessions were analysed for total phenolic content (TPC) by Folin-Ciocalteu method and antioxidant capacity (AOC) by DPPH and FRAP assays. The TPC of samples showed that the result of extraction methods is dependent on the solvent: MeOH extracts produced higher values by the US method while WA extracts gave better contents by Soxhlet. Concerning radical scavenging activity (DPPH) and ferrous reducing activity (FRAP), both values were higher in samples produced by US extraction method using WA as solvent. Large variability of TPC and AOC of the 36 plant samples indicates high diversity in polyphenol composition.