*3.4.3. Iron chelating properties of esculin and polyesculin fractions*

Polyesculin fractions exhibited high degree of iron chelating activity, according to the sitespecific hydroxyl radical-scavenging assay (Table 3). Results showed that iron chelating capacity was high as the *Mw* ¯ increases. The best iron chelating power was observed in the presence of the E5 fraction (IC50=180 µM), which was 37-folds better than esculin (IC50=6800 µM).

## *3.4.4. CUPRAC of esculin and polyesculin fractions*

Table 3 indicated that polyesculin fractions presented higher TEAC than esculin. This activity rose as the *Mw* ¯ increased. Therefore, the best cupric reducing antioxidant capacity was seen with the E5 fraction which was 30-folds more active than esculin.

## **3.5. Structure-antioxidant activity relationship**

The structure-antioxidant activity relationship of monomeric flavonoids and coumarins was well investigated. According to many authors [43] free hydroxyl groups on C4', C3' and C7 played a major role in antiradical activity of rutin and esculin. However, few data are available about the behaviour of these activities with polymerization. In this work we observed a decrease of polyrutin antiradical activities with *Mw* ¯ increase. This decrease could be attributed to the loss of these groups during the rutin polymerization reaction.

For high iron chelating power and CUPRAC, hydroxyl groups on C5, C3 and the 4 oxo (for flavonoids) and hydroxyl groups and catechol moiety (for coumarins) were essential. So, high iron chelating and cupric reducing antioxidant capacities observed with polyrutin and polyesculin fractions suggested that these groups were not implicated in the linkage occurred in rutin polymerization reaction [44-47].

For high xanthine oxidase inhibition activity, several works reported the importance of the presence of a double bond between C2 and C3 and free hydroxyl groups on C5 and C7 [26, 48-50]. High inhibition of the xanthine oxidase obtained in the presence of polyrutin and polyesculin fractions implicated that these groups are not affected during the polymerization reaction.
