Research noteIsolation of three curcuminoids for stability and simultaneous determination of only using one single standard substance in turmeric colour principles by HPLC with ternary gradient system

Based on high purities of curcumin, demethoxycurcumin and bisdemethoxycurcumin obtained by isolation and identified by NMR, MS and HPLC, this paper firstly studied feasibility of the method by HPLC, which used curcumin, the easily available constituent, as the external standard to directly determine the content of itself, and the same component in the analyte rather than the external component, as the internal standard to simultaneously determine the other two curcuminoids in turmeric source materials. Further, the stabilities of them alone or coexistence in turmeric colour principles were explored. The result showed that there were no significant differences between the present method and the external standard method conventionally used. And we found that demethoxycurcumin rather than curcumin and bisdemethoxycurcumin was quite instable. Thus, the study provided an alternative method to simultaneously determine three curcuminoids without multiple chemical standard substances and some valuable insight for the use of retaining demethoxycurcumin efficacy.