Bioactivity and anthocyanin content of microwave-assisted subcritical water extracts of Manipur black rice (Chakhao) bran and straw

Chakhao, the Geographical Indication (GI) tagged aromatic black rice of Manipur, India, is a rich source of bioactive compounds such as anthocyanins. However, there is limited work available on Chakhao and research has focused on its grain. No reports on the anthocyanin, antioxidant properties or in vitro bioactivities of its straw are available. Anthocyanins content of its different fractions displayed a positive correlation with their antioxidant potentials (r = 0.90). In this study, microwave-assisted sub-critical water extraction, at 90 °C for 5 min, from the straw gave an anthocyanins extraction efficiency of 85.8%. Furthermore, this microwave extract displayed higher antioxidant activity than an equivalent conventional methanol extract. In vitro studies on the microwave extracts of both straw and bran showed no apparent cytotoxicity on Jurkat cells and dose-dependent inhibition of colony growth in colorectal cancer cells. Black rice bran and straw are valuable by-products of the food industry that are rich in phytochemicals. This study reports the extraction of anthocyanins from black rice straw and presents evidence that the straw, in addition to the bran, contains important bioactive compounds; the extracts of which could further be explored as a natural antioxidant and/or functional ingredients

Subcritical solvent extraction of total anthocyanins from dried purple waxy corn: Influence of process conditions

Total anthocyanin content in different dried parts of purple waxy corn (Zea mays L. var. ceratina) genotype Fancy Muang 111 was investigated under subcritical solvent extraction. The highest total anthocyanin content of 991.4, 1241.5, and 1552.1 µg cyanidin-3-glucoside per gram dry weight of sample were obtained from dried kernel extraction (water–ethanol at ratio 1:3 as solvent and sample–solvent at ratio 1:20), dried cob extraction (water–ethanol at ratio 1:1 as solvent and sample–solvent at ratio 1:20), dried silk extraction (water–ethanol ratio at 1:1 as solvent and sample–solvent ratio at 1:30), respectively. The extraction was conducted at 100°C for 15 min with N2 purging. Additionally, the antioxidant activities assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays showed that the dried silk extract exhibited the greatest antioxidant activity in DPPH assay (IC50 = 3.2 mg/mL), ABTS assay (IC50 = 1.3 mg/mL), and FRAP assay (634.8 mmol FeSO4/100 g dry weight of sample). The extract powder had the total anthocyanin content of 632.8 µg cyanidin-3-glucoside/g powder. Practical applications The anthocyanin extraction from different dried parts of purple waxy corn was investigated by subcritical solvent extraction method. The effect of different parameters such as weight ratio of purple waxy corn samples to water, extraction temperature, extraction time, water-to-ethanol ratio as solvent, and oxygen in the subcritical solvent extraction provided high total anthocyanin content in the extraction, and the dried silk extract containing the highest total anthocyanin content exhibited the greatest antioxidant activity. Therefore, subcritical solvent extraction of total anthocyanins from purple waxy corn has been shown to be feasible and could be applicable in food processing industries. The total anthocyanin extract obtained has the potential to be developed into new health foods and to be used for the production of value-added products