Phytochemical and functional studies on the roots of Armoracia rusticana

Roots of horseradish (Armoracia rusticana G.Gaertn, B.Mey. & Scherb.) are used within rational phytotherapy against infections of the upper respiratory tract and the urogenital system due to their content of glucosinolates, which by enzymatic catalysis decompose to the antibacterial isothiocyanates, also known as mustard oils. In order to investigate if other compounds than mustard oils or their progenitors contribute to the antibacterial activity, a 70% methanol extract was prepared of horseradish roots and fractionated on Sephadex LH20, silica, and RP18. Prior to functional testing within different in vitro assays, the extract and the respective fractions were fermented by using a protein extract from horseradish roots to release mustard oils and allow for the potential conversion of other natural compounds. As expected, strong antibacterial activity against uropathogenic Escherichia coli (UPEC, strains UTI89 and NU14) and Pseudomonas aeruginosa (strains ATCC 9027 and ATCC 27853) was found with fermented extract, whereas the unfermented extract was inactive. Unfermented extract however showed a significant antiadhesive effect by about 50% against UPEC NU14 and does not influence cell viability of T24 bladder cells. Phytochemical analysis of extracts and fractions by UHPLC-qTOF-ESIMS indicated the presence of flavonoids, glucosinolates, and phospholipids hitherto not described for the genus Armoracia. In total, 60 different compounds were identified or widely characterized on the basis of these data. Differences in the flavonoid profiles of main and lateral roots and of fermented and non-fermented horse radish extract were identified by means of multivariate statistics.