Toxic effects of protoberberine alkaloids from Rhizoma Coptidis on Tetrahymena thermophila BF₅ growth based on microcalorimetry A reliable evaluation method of structure–function relationship

摘要

Rhizoma Coptidis consists mainly of protoberberine alkaloids (PAs), and has been used for many years as a traditional medicine. Recent research revealed the toxicity of Rhizoma Coptidis, but studies focusing on the relationships between the structures of PAs and their toxicities are lacking. The toxic effects of four PAs from Rhizoma Coptidis on the growth of Tetrahymena thermophila BF₅ were investigated by microcalorimetry. The power-time curves of T. thermophila BF₅ with and without PAs were obtained; the extent and duration of toxic effects on the metabolism of this organism were evaluated by studying thermokinetic parameters and the half-inhibitory ratio (IC ₅₀). All the thermokinetic parameters showed regular variations with alteration of PA concentrations. The magnitude of the toxic effects of PAs was ascertained from IC ₅₀ values: palmatine > jateorhizine > berberine ≈ coptisine. The structure–function relationship of PAs indicated that the C2 and C3 positions contributed more to the toxic effect of PAs. That is, when substituted with methoxyl groups, the toxic effect would be increased.