The aqueous lemon balm extract efficiently inhibits HIV-1 virion-fusion and results in a concordant inhibition of HIV-1 replication. (A) HIV-1NL4-3 virions carrying BlaM-Vpr were exposed to lemon balm extract at concentrations from 0.001 to 1% for 1 h at 37°C, and subsequently added to C8166 T-cells. Alternatively, T-cells were pretreated with AMD3100, enfuvirtide, or efavirenz for 15 min. Virion fusion was analyzed by multiparameter flow cytometry as reported [17, 29]. Shown are representative FACS dot plots for the detection of CCF2 substrate cleavage. (B) A replication assay with an experimental set-up analogous to that described in the legend to Fig. 1 was performed with the identical virus stock used in the virion-fusion assay. (C) MTT viability assay. Each experiment was performed in triplicate, and four independent experiments were conducted. Given are arithmetic means ± SD from one experiment.