Use of Equilibrium Dialysis to Estimate the Size of Active Materials in Natural Product Extracts

Many different criteria are used to prioritize natural product leads. Among them is molecular weight, since high-molecular-weight species are frequently not suitable for chemistry programs. The commonly used techniques for sizing are time consuming and tedious. Large volumes are needed and the samples have to be dried down and normalized prior to assay. The method described here is rapid, allows up to 24 samples to be sized simultaneously, and the samples can be assayed without any further work-up. The analysis can be done with small volumes, usually less than 1 ml, and as low as 10 μl. Also described are results that were obtained from the analysis of 20 lead natural product extracts identified in tyrosine kinase screens.