Identification of compounds responsible for anti-hRSV activity. (A) Inhibitory activity of isolated compounds toward viral protein synthesis. A549 cells were treated with the indicated compounds 1 hour prior to hRSV infection (MOI 0.5). cDNAs were synthesized from total RNA isolated from cells 24 hours after infection. The relative amount of RNA for hRSV NS2 and SH protein were determined by RT-qPCR. Data represent means ± SD. ** p < 0.01 versus Mock-treated (Mock). A.U.: Arbitrary unit. (B) Comparison of inhibitory activities of carnosic acid, catechol, and carnosol. Effects of carnosic acid (carnosic), catechol, and carnosol on the synthesis of hRSV F protein RNA was determined as in (A). Data represent means ± SD. ** p < 0.01 versus Mock-treated (Mock). A.U.: Arbitrary unit.