Antiradical activity and phenolic constituents of Stachys recta L. subsp. recta herb methanol extract

Abstract

The highest richness of taxa within genus Stachys was recorded in the wider area of the Mediterranean, where the group S. recta stands out in terms of taxonomic complexity. The center of diversity of this group is on the Balkan Peninsula. Its representatives are still insufficiently defined in taxonomic and horological terms, and their traditional approach includes about fifteen taxa, mostly at the infraspecific level. Despite some radical approaches that were presented at the end of the last century [1], the traditional taxonomic treatment is still prevailed in the relevant global lists. In this work antiradical potential and phenolic constituents of S. recta L. subsp. recta were investigated. Plant material, collected in Central Serbia (vicinity of Prokuplje), was air-dried, powdered, and then extracted by bimaceration with chloroform and methanol. Obtained dry methanol extract exhibited strong, concentration-dependant anti-DPPH activity (SC50=8.23 μg/mL), with total phenolics content at 0.27 mg GAE/mg of dry extract. In TLC-DPPH test observed yellow zones indicated presence of few compounds which strongly neutralized purple DPPH radical. LC-MS analysis revealed presence of 24 phenolic compounds, belonging to three classes of constituents: phenolic acids, phenylethanol glycosides and flavonoids. Chlorogenic acid (2.63%) was the only phenolic acid, while acteoside was the most dominant phenylethanoid (24.03%). Flavonoid fraction was composed almost entirely of 8-hydroxyflavones, derivatives of hypolaetine and isoscutellareine (53.47%). The most prominent flavonoids in investigated extract were 7-O-[6'''-acetylallosyl(1®2)]-glucopyranosides of 4'-O-methylhypolaetine and hypolaetine (15.92 and 13.01%, respectively).