Table 6. Antioxidant activity of extracts, their derived fractions and the compounds isolated from D. bulbifera, as evaluated by DPPH and hydroxyl radical scavenging.
| No | Sample | IC50 (μM) | |
|---|---|---|---|
| DPPH radical | Hydroxyl Radical | ||
| 1c | EtOH extract | 34.14 ± 0.68* | 79.00 ± 0.78* |
| 2c | Water extract | 13.20 ± 0.77* | >100 |
| 3c | CHCl3 fraction | 13.35 ± 0.37* | >100 |
| 4c | EtOAc fraction | 14.00 ± 0.36* | 37.04 ± 0.50* |
| 5c | Water fraction | 18.83 ± 0.46* | 39.31 ± 0.42* |
| 6 | 8-Epidiosbulbin E acetate (1) | 80.87 ± 0.48* | >100 |
| 7 | 15,16-Epoxy-6α-O-acetyl-8β-hydroxy-19-nor-clero-13(16),14-diene-17,12;18,2-diolide (2) | 37.57 ± 1.27* | 51.90 ± 0.62* |
| 8 | Sitosterol-β-D-glucoside (3) | >100 | >100 |
| 9 | 3,5-Dimethoxyquercetin (4) | 9.02 ± 0.56* | 22.07 ± 0.94* |
| 10 | (+)-Catechin (5) | 8.27 ± 0.44* | 19.58 ± 0.27* |
| 11 | Quercetin (6) | 5.33 ± 0.25 | 16.80 ± 0.33* |
| 12 | Kaempferol (7) | 16.15 ± 0.25* | 51.68 ± 0.53* |
| 13 | Allantoin (8) | >100 | >100 |
| 14 | 2,4,3',5'-Tetrahydroxybibenzyl (9) | 16.20 ± 0.27* | 63.84 ± 0.54* |
| 15 | 2,4,6,7-Tetrahydroxy-9,10 dihydrophenanthrene (10) | 22.68 ± 0.54* | 71.55 ± 1.12* |
| 16 | Myricetin (11) | 4.87 ± 0.41 | 11.68 ± 0.39* |
| 17 | L-Ascorbic acid (positive control) | 3.99 ± 0.13 | ND |
| 18 | BHT (positive control) | ND | 4.06 ± 0.41 |
*Statistically significant difference between the positive control and sample, p < 0.05 (mean ± S.E.M. of three determinations).
cConcentration of treated samples and IC50 expressed in μg/ml.
ND = not determined.