Abstract: Biologically active compounds (e.g. from the groups of pharmaceutical drugs, cofactors, hormones, vitamins or phytochemicals) often consist of two or more stereoisomers (enantiomers or diastereoisomers) which may differ in their pharmacodynamic/kinetic, toxicological and biological properties. These differences are so far difficult to detect. A well known example for a biologically active compound and its counterpart is vitamin E which is predominantly administered as two different ‘forms’, one derived from natural sources (mainly soybeans), and one from production by chemical total-synthesis. While vitamin E from natural sources occurs as a single stereoisomer (RRR-?-tocopherol), so-called synthetic vitamin E (all-rac-?-tocopherol) is an equimolar mixture of eight stereoisomers. The present invention is directed to a method for calculating the biological activity of a biologically active compound (e.g. RRR-?-tocopherol) and a counterpart thereof (e.g.