Table 2.
Phenolic acid composition of raw white rice, cowpea, sorghum leaves, their composite blend, and cooked products.
| Sample | Raw Rice | Raw Cowpea | Raw Leaves | Raw Mix | Boiled Rice | Cooked Rice–Cowpea Blend | Total |
|---|---|---|---|---|---|---|---|
| Soluble free phenolics | |||||||
| p-hydroxybenzaldehyde | 22.1 ± 0.2 b | nd | nd | nd | 1.5 ± 0.0 a | nd | 23.6 ± 0.2 D |
| p-coumaric acid | 20.4 ± 0.6 a | nd | nd | nd | 22.4 ± 2.3 a | nd | 42.8 ± 2.1 F |
| p-coumaroyl aldaric acid | nd | 13.8 ± 1.2 b | nd | 5.5 ± 0.0 a | nd | 5.0 ± 0.1 a | 24.3 ± 1.4 D |
| p-coumaroyl aldaric acid | nd | nd | nd | nd | nd | 6.7 ± 0.1 a | 6.7 ± 0.1 B |
| Feruloyl methylaldaric acid | nd | nd | nd | 20.0 ± 2.0 a | nd | nd | 20.0 ± 2.0 D |
| Feruloylaldaric acid | nd | 19.6 ± 1.6 c | nd | 1.2 ± 0.0 a | nd | 10.0 ± 0.8 b | 30.8 ± 1.7 E |
| Feruloylaldaric acid | nd | 9.7 ± 0.9 a | nd | nd | nd | nd | 9.7 ± 0.9 B |
| Feruloyl methylaldaric acid | nd | 8.1 ± 0.4 a | nd | 2.0 ± 0.2 a | nd | 1.5 ± 0.1 a | 11.6 ± 0.4 B |
| Feruloyl methylaldaric acid | nd | 20.4 ± 0.7 b | nd | 21.8 ± 2.9 a | nd | 10.2 ± 0.3 a | 52.4 ± 0.4 G |
| Feruloyl methylaldaric acid | nd | 15.8 ± 0.8 a | nd | nd | nd | nd | 15.8 ± 0.8 C |
| 1,3-coumaroyl-feruloyl-glycerol | nd | 3.3 ± 0.1 a | nd | nd | nd | nd | 3.3 ± 0.1 A |
| Total | 42.5 ± 0.5 C | 90.7 ± 1.9 E | nd | 50.5 ± 1.2 D | 23.9 ± 2.0 A | 33.4 ± 0.4 B | |
| Insoluble bound phenolics | |||||||
| protocatechuic aldehyde | nd | 28.6 ± 0.5 c | nd | 13.4 ± 0.4 a | 17.5 ± 0.3 b | nd | 59.4 ± 0.5 B |
| p-hydroxybenzaldehyde | nd | nd | nd | nd | nd | nd | nd |
| 2,4-dihydroxy benzoic acid | nd | 17.2 ± 0.3 c | nd | 12.8 ± 0.8 b | 3.8 ± 0.1 a | nd | 33.8 ± 0.6 A |
| p-coumaric acid | 5.6 ± 0.4 a | 37.3 ± 0.2 c | 4208.1 ± 22.3 e | 50.7 ± 0.4 d | 24.3 ± 0.0 b | nd | 4326.1 ± 22.1 D |
| ferulic acid | 38.8 ± 1.3 b | 23.0 ± 0.1 a | nd | 40.0 ± 0.1 b | 39.8 ± 0.3 b | 39.5 ± 0.1 b | 181.2 ± 1.6 C |
| Total | 44.4 ± 1.7 B | 106.2 ± 1.0 D | 4208.1 ± 22.3 F | 116.9 ± 1.2 E | 85.5 ± 0.7 C | 39.5 ± 0.1 A | |
Key: protocatechuic aldehyde was quantified and expressed as protocatechuic acid equivalent; p-hydroxybenzaldehyde was quantified and expressed as p-hydroxybenzoic acid equivalent; coumaroylaldaric acids were quantified and expressed as p-coumaric acid equivalent; feruloyl aldaric acids, feruloyl methylaldaric acids, and 1,3-coumaroyl-feruloyl-glycerol were quantified and expressed as ferulic acid equivalent. Results were presented as means ± standard deviation of triplicates. Results were expressed as µg/g sample, dry weight basis. Values in a row with same superscript letters were not significantly (p < 0.0001) different from each other. nd = not detected. Significant differences among means of measured variables are shown by lowercase superscripts, while significant differences among means of total values are denoted by uppercase superscripts.