Microcalorimetric investigation of the toxic action of berberine on Tetrahymena thermophila BF(5).

Tetrahymena thermophila (T. thermophila) BF(5) produces heat through growth and metabolism. By microcalorimetry, the power-time curves of the metabolism of T. thermophila BF(5) at 28 °C were measured and some quantitative parameters were obtained from these curves. Then the action of berberine on this microbe was investigated. Furthermore, the minimum inhibitory concentration (MIC) of berberine against T. thermophila BF(5) growth was obtained by tube dilution method. Berberine of different concentrations had various actions on T. thermophila BF(5) growth: a low concentration (25 μg/ml) of berberine began to inhibit the growth of T. thermophila BF(5) and a high concentration (450 μg/ml) of berberine completely inhibited T. thermophila BF(5) growth. The toxic action of berberine could also be expressed as half-inhibitory concentration IC(50), i.e., 50% effective in this inhibition. The value of IC(50) was 175.60 μg/ml, while the MIC of this compound against T. thermophila BF(5) was 20.76 mg/ml. Berberine has strong toxic action on T. thermophila BF(5) growth. The microcalorimetric method for the assay of toxic action is quantitative, inexpensive and versatile.