Chemical Composition, Antiviral and Antiproliferative Activity of Extracts from Agrimonia eupatoria L.

The limited spectrum of currently available antiviral drugs and the emergence of viral resistance highlight the need for novel antiviral agents with broad-spectrum activity and low toxicity. Agrimonia eupatoria L. (Rosaceae) is a medicinal plant rich in phenolic compounds with diverse biological activities. The present study investigated the phytochemical composition and antiviral and antiproliferative activities of methanolic (Ae-M) and hydromethanolic (Ae-WM) extracts of A. eupatoria. HPLC–HRMS/MS analysis revealed 28 phenolic constituents, predominantly flavonoid glycosides, flavan-3-ols, hydrolysable tannins and hydroxycinnamic acid derivatives. Semi-quantitative analysis revealed luteolin 7-O-glucoside, isoquercetin, hyperoside and agrimoniin as the major constituents. Both extracts exhibited low cytotoxicity and no detectable phototoxicity. Antiviral assays revealed inhibitory effects against herpes simplex virus type 1 (HSV-1) and human coronavirus OC43 (HCoV-OC43), with greater activity against HSV-1 (selectivity indices of 14.3–16.2 for both extracts). Additionally, both extracts exhibited pronounced virucidal activity against both viruses, reducing viral titers by Δlg = 2 to 3. They also completely inhibited HSV-1 adsorption to MDBK cells (with a reduction in Δlg = 5) and protected healthy cells from viral infection, with the strongest protective effect observed against HCoV-OC43, with a reduction in Δlg = 3.75. In addition, both extracts showed selective antiproliferative activity against MCF-7 and MDA-MB-231 breast cancer cells compared with non-tumorigenic MCF-12F cells. Overall, these findings identify A. eupatoria as a promising source of phenolic-rich extracts exhibiting in vitro antiviral and antiproliferative activities and support further investigation of their biological potential.