Galium aparine L., family Rubiaceae, is a widely spread species in the Galium genus. The herb of G. aparine is part of folk remedies and dietary supplements. In this study, we analyzed the chemical composition and immunomodulatory activities of G. aparine herb ethanolic extracts obtained from the plant material by maceration with 20%, 60% or 96% ethanol. The contents of hydroxycinnamic acid derivatives, flavonoids and polyphenols were determined spectrophotometrically, with extractives and polysaccharides quantified gravimetrically. The qualitative composition was studied using UHPLC-DAD-MS/MS analysis; isolation not previously described in G. aparine quercetin rhamnoglucoside was carried out through column chromatography, and the immunomodulatory activity of extracts was determined in the reaction of lymphocyte blast transformation. Major constitutes of extracts were iridoids, i.e., monotropein, 10-desacetylasperulosidic acid and asperulosidic acid; p-hydroxybenzoic acid; hydroxycinnamic acid derivatives, i.e., 3-O-caffeoylquinic, 5-O-caffeoylquinic, 3,4-O-dicaffeoylquinic, 3,5-O-dicaffeoylquinic, 4,5-O-dicaffeoylquinic acids and caffeic acid derivatives; flavonoids, i.e., rutin, quercetin 3-O-rhamnoglucoside-7-O-glucoside, and isorhamnetin 3-O-glucorhamnoside. Significantly, quercetin 3-O-rhamnoglucoside-7-O-glucoside was first isolated and identified in Galium species so far investigated. All G. aparine herb ethanolic extracts stimulate the transformational activity of immunocompetent blood cells, with 96% ethanolic extract being the most active. The data obtained necessitate further research into the mechanisms of immunomodulatory activity of extracts from G. aparine herb.Specific immunostimulants include thymus preparations, interleukins, interferons, biologically active peptides, polysaccharides of certain fungi and therapeutic vaccines, whose effect is explained through their ability to influence the metabolism of cells and body tissues and activate immunocompetent cells.Many plant-derived compounds, like sterols, polysaccharides, alkaloids, flavonoids, lectins and glycoprotein, are used for immunomodulation [3]. For example, among polysaccharides, acidic arabinogalactan and ramnogalacturonan have been shown to manifest immunostimulatory effect in vitro and in vivo [4]. Numerous studies look into the immunomodulative activities of saponins [5][6][7][8].The proven effect of triterpenoid glycosides on the immune system of mammals contributed to the development of a wide range of dietary supplements for the prevention of the immune system disturbances, i.e., human immunity system enhancement [9], and for the prevention and treatment of allergies [10,11].In our previous studies, the immunomodulative effect of the aqueous and ethanolic extracts of Galium verum L. herb was established [12,13]. Among other species of the genus Galium L., one of the most widely spread is Galium aparine L., also called cleavers or goosegrass, which can be found all over Ukraine, Europe, Northern America and certain parts of Asia; i...
