Nutritional, phytochemical and antioxidant properties of Bangladeshi pigmented rice (red and black), grains and pseudograins

A comprehensive nutritional and phytochemical study of Bangladeshi cereals and pseudograins is required to demonstrate their significance as functional foods. Black and red aman (rainy to winter season) rice (Oryza sativa), wheat (Triticum aestivum), maize (Zea mays), oat (Avena sativa), black and yellow buckwheat (Fagopyrum esculentum), chia (Salvia hispanica) and quinoa (Chenopodium quinoa) have been analysed for their proximate composition, total phenolics, flavonoid and antioxidant capacity, DPPH activity, ABTS activity, FRAP assay and HPLC polyphenol profiling. Chia showed highest protein, fat and dietary fibre contents among all samples. Black rice extract contained higher amounts of TAC, TPC, and TFC while yellow buckwheat exhibited the highest TAC (176.33 mg AAE/100 g) activity. Black rice among cereal samples revealed the most TPC (90.58 mg GAE/100 g) and TFC (58.84 mg QE/100). The HPLC profiling of polyphenol revealed that red aman rice and quinoa contained highest epicatechin concentration (13.05 and 104.26 mg/100 gm in dry extract). On the other hand, red aman rice and black buckwheat extracts showed the lowest IC₅₀ values in ABTS (19.00 and 9.35 µg/mL) and DPPH (9.35 and 43.45 µg/mL) assays. In FRAP test, methanolic grain extracts depicted significantly higher reducing power compared to the standard. Therefore, these cereals and pseudograins showed bioactive polyphenolic compounds that may be useful in dietary management of various diseases.