Figure 8: Real-time PCR analysis of expression of several virulence factor genes. Streptococcus mutans was cultured and treated with various concentrations of kaurenoic acid (KA) and real-time PCR analysis was then performed as described in Section 2. gtfB, gtfC, and brpA expressions were significantly inhibited at 3 μg/mL of KA, but gtfD expression was not inhibited. gbpB and spaP were significantly inhibited at 2 and 3 μg/mL of KA. The expression of relA was inhibited ranging over 1–3 μg/mL KA. vicR expression was inhibited at 1 and 3 μg/mL of KA. Each value is expressed as a mean ± standard deviation. Significance was determined at when compared with the control.