The self-nanoemulsifying drug delivery system has shown many advantages in drug delivery.In this study,a self-nanoemulsifying drug delivery system of buckwheat flavonoids was prepared for enhancing its antioxidant activity and oral bioavailability.A nanoemulsion of buckwheat flavonoids was developed and characterized,and its antioxidant,in vitro release,and in vivo bioavailability were determined.The nanoemulsion was optimized by the central composite design response sur-face experiment,and its particle size,polymer dispersity index(PDI),zeta potential,morphology,encapsulation efficiency,and stability were evaluated.The antioxidant activity was tested by mea-suring its 2,2-diphenyl-1-picrylhydrazyl scavenging activity,hydroxyl radical scavenging activity,and superoxide anion scavenging ability.In vitro release of buckwheat flavonoids nanoemulsion showed a higher cumulative release than the suspension,and the release fitting model followed the Ritger-Peppas and Weibull models.The effective concentration of the nanoemulsion was eval-uated in vivo using a Wistar rat model,and the area under the plasma concentration-time curve of the buckwheat flavonoids nanoemulsion was 2.2-fold higher than that of the buckwheat flavonoid suspension.The Cmax of the nanoemulsion was 2.6-fold greater than that of the suspension.These results indicate that the nanoemulsion is a promising oral drug delivery system that can improve the oral bioavailability to satisfy the clinical requirements.