Chemical constituents from Chirita longgangensis var. hongyao with inhibitory activity against porcine respiratory and reproductive syndrome virus

Two new quinonoids chiritalone A and B, and a new neolignan 7’E-4,9-dihydroxy-3,3′,5′-trimethoxy-8,4′-oxyneolign-7′-en-9′-al, along with known (-)-8-hydroxy-α-dunnione, digiferruginol, 2,5-dimethoxy-1,4-benzoquinone and hederagenin, were isolated from the stems of Chirita longgangensis var. hongyao. The structures of the new compounds were elucidated by detailed analysis from NMR (nuclear magnetic resonance) and MS (mass spectrometry) data, and the absolute configuration of chiritalone A was determined by single crystal X-ray diffraction analysis using the Flack parameter. The inhibitory activity of compounds against porcine respiratory and reproductive syndrome virus (PRRSV) was measured by the cytopathic effect (CPE) method. Digiferruginol and hederagenin showed weak effect on PRRSV with an IC50 value of 80.5 ± 16.9 µmol L-1 (SI = 19.9) and 43.2 ± 7.4 µmol L-1 (SI = 13.1), respectively.