Unraveling the nutritional and therapeutic properties of ‘Kavuni’ a traditional rice variety of Tamil Nadu

‘Kavuni’ a traditional brownish black rice variety is known for its anti-diabetic properties and is grown under limited areas of Tamil Nadu, India. The present study was aimed at profiling the nutritional and therapeutic values of Kavuni grains in comparison with three other popularly eaten white rice varieties of Tamil Nadu viz., CO 50, IR64 and White Ponni. Biochemical analysis revealed the significant differences in the nutritional composition of Kavuni grains when compared to other three white rice genotypes viz., 29–35 % reduced level of total soluble sugars, low fat content (8–35 %), 21–52 % increased dietary fibre and 7–24 % increased total protein content. Kavuni grains had significantly higher amount of iron (20–30 %), calcium (33–45 %), copper (9.5–14.7 %), sodium (21–38 %), potassium (7–15 %) and magnesium (8.9–26 %). GC-MS analysis showed that phenolic acids and flavonoids were predominant in the Kavuni grains whereas sugars and fatty acids were predominant in the grains of a white rice variety CO 50. Further, Kavuni was found to possess significantly higher levels of different carotenoids (β-carotene—46.2 μg/100 g; lutein—221.6 μg/100 g), total phenolics (28.8 μg/100 g) and higher anti-oxidant activity. Methanol and ethyl acetate extracts of Kavuni grains were found to exhibit significantly higher level of inhibitory activity against α-amylase and α-glucosidase than the extracts of CO 50 (α-amylase IC50—0.1, 1.0 μg/ml and α-glucosidase IC50 0.04, 0.05 μg/ml).