Correlation between iridoid glycoside contents represented by the combination of shanzhiside methylester and 8-O-acetyl-shanzhiside methylester from the Lamiophlomis rotata extract samples (table 1) and their half-effective dose (ED₅₀) values (in formalin-induced tonic hyperalgesia) in a nonlinear regression of one-phase exponential decay (A) and 1/ED₅₀ values in a linear regression (B). The statistical significance was calculated for both correlations (P < 0.05 by the two-tailed Student t test).