Meroterpenoids with anti-triple negative breast cancer and antimicrobial activities from Arnebia euchroma

Two new meroterpenoids, arneuchrols A and B (1 and 2), together with twelve known analogs (3-14) were isolated from the root of Arnebia euchroma. The structures of 1 and 2 including their absolute configurations were elucidated by NMR, HRESIMS, and DFT calculation of their NMR and ECD data. The structure of pseudoshikonin I, firstly isolated from Lithospermi radix was revised as shikonofuran E (4). Anti-triple negative breast cancer (anti-TNBC) and antimicrobial activities of the isolated compounds were tested. Compounds 3, 4, 6, 7, 9, 10, and 13 exhibited potent inhibitory activity against TNBC (MDA-MB-231 cells) with IC₅₀ values in the range of 0.18-4.58 μM. Compound 10 displayed antifungal activity against five plant pathogenic fungi with MIC values in the range of 6.25-25 μg/mL. Compound 9 exhibited antibacterial activity against Micrococcus lysodeikticus with MIC value of 12.5 μg/mL.