Doc:Antioxidant
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Antioxidant Activity of Flavonoid
In vitro study
The reactivity of an antioxidant is determined by its reactivity as a hydrogen or electron-donating agent, the fate of the resulting radical (unpaired electron), its reactivity with other antioxidant, and its metal-chelating potential. The reactivity can be assessed by applying the chromogenic redox indicator ABTS+(radical cation of 2,2'-azino-bis (3-ethylbenzthiazoline 6-sulphonic acid) relative to Trolox (water-soluble vitamin E analogue).
The strength of antioxidant activities is ordered as:
- the ortho 3',4'-dihydoroxy moiety in the B-ring,
- the meta 5,7-dihydroxy moiety in the A-ring, and
- the 2,3-double bond together with both 4-keto and 3/5-hydroxy group in the C-ring.
For example, quercetin is a more effective photoprotectant and anti-oxidant than kaempferol. [1] [2]
- ↑ Ryan KG, Swinny EE, Markham KR, Winefield C (2002) "Flavonoid gene expression and UV photoprotection in transgenic and mutant Penunia leaves" Phytochem 59:23-32 PMID 11754940
- ↑ Li J, Ou-Lee T-M, Raba R, Amundson RG, Last RL (1993) "Arabidopsis flavonoid mutants are hypersensitive to UV-B irradiation" Plant Cell 5: 171-179 PMID 12271060
In vivo study
Although antioxidant activities of flavonoids are several times higher than vitamin C or E in vitro, their plasma and intracellular concentration after intake is 100-1000 times lower than vitamin C. The antioxidant function in vivo is therefore considered negligible[1].
- ↑ Frei B, Higdon JV (2003) "Antioxidant activity of tea polyphenols in vivo: evidence from animal studies" J Nutr 133(10):3275S-3284S
| Relative total antioxidant activities[1] | ||
|---|---|---|
| Antioxidant | Sources | Activity* (mM) |
| Vitamins | ||
| Vitamin C | fruit and vegetables | 1.0 ± 0.02 |
| Vitamin E | grains, nuts and oils | 1.0 ± 0.03 |
| Anthocyanins | ||
| Oenin | black grapes/red wine | 1.8 ± 0.02 |
| Cyanidin | grapes, raspberries and strawberries | 4.4 ± 0.12 |
| Delphinidin | aubergine skin | 4.4 ± 0.11 |
| Flavonols | ||
| Quercetin | onion, apple skin, berries, black grapes, tea and broccoli | 4.7 ± 0.10 |
| Kaempferol | endive, leek, broccoli, grapefruit and tea | 1.3 ± 0.08 |
| Flavones | ||
| Rutin | onion, apple skin, berries, black grapes, tea and broccoli | 2.4 ± 0.12 |
| Luteolin | lemon, olive, celery and red pepper | 2.1 ± 0.05 |
| Chrysin | fruit skin | 1.4 ± 0.07 |
| Apigenin | celery and parsley | 1.5 ± 0.08 |
| Flavan 3-ols | ||
| (Epi)catechin | black grapes/red wine | 2.4 ± 0.02 |
| Epigallocatechin | teas | 3.8 ± 0.06 |
| Epigallocatechin gallate | teas | 4.8 ± 0.06 |
| Epicatechin gallate | teas | 4.9 ± 0.02 |
| Flavanones | ||
| Taxifolin | citrus fruit | 1.9 ± 0.03 |
| Naringenin 7-rutinoside | citrus fruit | 0.8 ± 0.5 |
| Naringenin | citrus fruit | 1.5 ± 0.05 |
| Hesperetin 7-rutinoside | orange juice | 1.0 ± 0.03 |
| Hesperetin | orange juice | 1.4 ± 0.08 |
| Teaflavins | ||
| Teaflavin | black tea | 2.9 ± 0.08 |
| Teaflavin 3-gallate | black tea | 4.7 ± 0.16 |
| Teaflavin 3'-gallate | black tea | 4.8 ± 0.19 |
| Teaflavin digallate | black tea | 6.2 ± 0.43 |
| Hydroxycinnamates | ||
| Caffic acid | white grapes, olive, cabbage and asparagus | 1.3 ± 0.01 |
| Chlorogenic acid | apple, pear, cherry, tomato and peach | 1.3 ± 0.02 |
| Ferulic acid | grains, tomato, cabbage and asparagus | 1.9 ± 0.02 |
| p-Coumaric acid | white grapes, tomato, cabbage and asparagus | 2.2 ± 0.06 |
| * ... Measured as the Trolox equivalent antioxidant activity (TEAC) - the concentration of Trolox with the equivalent antioxidant activity of a 1 mM concentration of the experimental substance | ||
- ↑ Rice-Evans C, Miller N, Paganga G (1997) "Antioxidant properties of phenolic compounds" Trends Plant Sci 2(4):152-159
