The generally useful estimate of solvent systems method enables the rapid separation of curcuminoids by countercurrent separation

The Generally Useful Estimate of Solvent Systems (GUESS) method was originally developed for the selection of countercurrent separation (CCS) solvent systems. It was shown if an analyte can be eluted at Rf value ≈ 0.5 by the organic phase or an equivalent organic-only solvent system on NP-TLC, the analyte will be delivered into the distribution coefficient (K value) sweet spot range by the matching solvent system in CCS. However, although > 100 research papers have cited the original GUESS publication since 2005, few of them have actually applied the predictive TLC part of the method. The current study demonstrates the rapid prediction power of the GUESS method for CCS solvent systems. It tested three curcuminoids in n-hexane-EtOAc-MeOH-Water, CHCl₃-MeOH-Water and n-hexane-CHCl₃-MeOH-Water solvent system families. When developing with the organic phase of n-hexane-CHCl₃-MeOH-Water (3:7:7:3, v/v), the TLC Rf values of curcumin, demethoxycurcumin, and bisdemethoxycurcumin were 0.50, 0.46, and 0.38, while their measured K values were 0.57, 0.97, and 1.91 in normal phase CCS. The present study indicates that the GUESS method can facilitate natural product separation by CCS.