The purified equine MPO used in these experiments was the same as that used by Franck et al. (2006) to develop the SIEFED technique. All the

extracts, including the isoorientin standard, exhibited inhibitory effects on MPO activity (Fig. 3). Similar dose-dependent inhibition of MPO was observed with P. edulis and P. alata pulp extracts, reaching approximately 50% of inhibition at the highest concentration tested (1.0 mg mL−1). However, the most potent inhibitory effect on the peroxidase activity of MPO was observed with the rind extracts, which showed a 50% inhibitory effect at 0.1 mg mL−1. The two rind extracts showed a similar dose-dependent inhibitory response except for the highest concentration of the infected rind find more extract which presented a slightly higher inhibition of MPO activity than the healthy rind (97% and 89%, respectively). MK8776 The originality of the SIEFED technique lies in its ability to measure the peroxidase activity of MPO after its immunological extraction and the elimination by washing of the excess of isoorientin or tested extracts. Therefore, if an inhibition of MPO activity is observed, it can be attributed solely to a direct interaction of the tested compound with the enzyme because the unbound molecules or compounds

have been discarded by the washing step (Franck et al., 2008 and Kohnen et al., 2007). These observations suggested that polyphenolic substances present in the rind extracts were fixed on MPO (on the active site of the enzyme or an amino acid of the protein structure) or altered the enzyme structure, leading to MPO inactivation. Our results indicated that isoorientin is able to interact directly with MPO, since at low concentrations, it inhibits MPO activity dose-dependently, with a 50% inhibitory effect reached at close to 4 μg mL−1. The flavonoids extracted from P. edulis pulp were identified by their characteristic UV spectral patterns: Band I, λmax around 300–380 nm and

Band II, λmax around 240–280 nm ( Mabry, Markhan, & Thomas, 1970). The flavone isoorientin was identified by comparison of its retention time (tr) and UV spectrum with an authentic old standard of isoorientin ( Fig. 4). The isoorientin content of passion fruit rinds (healthy and infected, Table 1) was considerably higher than that of passion fruit pulp. Recent studies have shown that many flavonoids, such as isoorientin and related polyphenols, contribute significantly to the antioxidant activity of many fruits and vegetables (Ko et al., 1998 and Luo et al., 2002). Previous studies have reported the anti-inflammatory activity of C-glycosyl flavones on mouse models. Küepeli, Aslan, Guerbuez, and Yesilada (2004) described the anti-inflammatory activity of isoorientin in the mouse carrageenan-induced paw oedema model, and, based on mouse models of pleurisy. Zucolotto et al. (2009) and Vargas et al. (2007) demonstrated that aqueous extracts and isoorientin from P.