Abstract: The fractions separated from light distillates of ginkgo lipids were prepared by extraction with petroleum ether, saponification, molecular distillation and silica gelcolumn chromatographic isolation. Four methods (DPPH, ABTS, superoxide anion and hydroxy radical) with Sigmoidal curve fitting method arriving at respective IC₅₀ values were used to determine the antioxidant effect of the seven fractions. The results showed that light distillates of ginkgo lipids had antioxidant effect and the fraction 2 (95% petroleum ether/5% acetic ether) had the highest antioxidant effect in all tested fractions. IC₅₀ values were (51.0±0.061), (51.3±0.042), (56.9±0.045) and (124.4±0.037)mg/L. The relative deviation between experimental scavenging rate and scavenging rate (50%) of the fraction having maximum deviation in all fractions was 1.4%. Consequently, it is reasonable that the IC₅₀ values of different polar fractions of light distillates separated from ginkgo lipids are generated with Sigmoidal curve fitting method.

Key words: Ginkgo biloba, Sigmoidal curve fitting method, lipids, antioxidant