Metabolomics revealed metabolite biomarkers of antioxidant properties and flavonoid metabolite accumulation in purple rice after grain filling

•The darker the colour of purple rice grain, the stronger the total antioxidant capacity.•The total antioxidant capacity at the early filling stage was lower than that at the middle and late filling stages.•Flavonoid synthesis in purple rice grains increased significantly 21 days after grain filling.•Phlorizin, myricetin 3-galactoside and trilobatin are metabolite biomarkers of antioxidant properties of purple rice grains.