Grains and beans are abundant in bioactive substances.This study investigated the bioactive substances in a multi-grains formula (MGF) composed of mung bean, tartary buckwheat, black rice, black sticky rice, oat germ rice, and white rice.Polyphenols and inositol (PIEs) were extracted from MGF before and after high-temperature air fluidization (HTAF) processing, and the antioxidant activity of the extract was evaluated in vitro.Results showed that the PIEs of MGF mainly contained phenolic acids, flavonoids, myo-inositol, and D-chiro-inositol.The highest scavenging rate of MGF PIEs for ABTS cationic free radicals, DPPH free radicals, and hydroxyl free radicals reached 92.28%, 75.02%, and 87.21%, respectively, and its scavenging ability increased in a concentration-dependent manner within a certain concentration range.At the same time, MGF PIEs also showed a certain total reducing capacity and Fe2+ chelating capacity, with the highest reaching 1.26 mg vitamin C equivalent /mL and 1.85 mmol Fe2+, respectively.After the HTAF process, the scavenging abilities for DPPH free radicals, total reducing capacity, and Fe2+ chelating capacity of MGF were further improved.The correlation analysis showed that total flavonoids and total polyphenols were the most critical antioxidant components of MGF.Their contents were significantly correlated with ABTS cationic radical scavenging capacity, hydroxyl radical scavenging capacity, and total reducing capacity (P<0.001), and the correlation was higher than that of myo-inositol and D-chiro-inositol (P<0.01).The total reducing capacity was the most representative antioxidant evaluation index of MGF.It was significantly correlated with total polyphenols (P<0.001), total flavonoids (P<0.001), myo-inositol (P<0.001), and D-chiro-inositol (P<0.01) contents.To sum up, the PIEs of MGF showed strong antioxidant activity, and HTAF treatment which improved the cooking quality of MGF could also retain or slightly improve the antioxidant activity of MGF.This research provided a certain theoretical basis for the prevention of oxidative stress metabolic diseases via multi-grain diets. [ABSTRACT FROM AUTHOR]