At pH 1 0 the anthocyanins were predominantly in the flavylium ca

At pH 1.0 the anthocyanins were predominantly in the flavylium cation form, whereas the proportion of this form significantly decreased at pH 3.0 and

almost disappeared at pH 5.0. In fact, at pH 5.0 the absence of absorption bands in the visible spectrum indicates that the this website anthocyanins present in the functional extract were mostly in the colourless forms of hemiacetals and/or chalcones (Table 5). Colour parameters are consistent with the results obtained by UV–Vis, considering that at pH 1 the hue (h  ab) value was in the red-purple region, and the chroma value was 2–20 times higher than those obtained at other pH conditions ( Table 5). In addition, the FE had the lowest values of C∗C∗ at pH 3 and 5 (1.4 and 0.5, respectively) due to high concentration of the colourless forms. Finally, the bathochromic shift in the UV–Vis spectra observed at pH 7.0 and 9.0 as compared to pH 1.0, along with the colour characteristics at pH 7 (C∗=5.1C∗=5.1 and hab in blue region) indicated a shift in the equilibrium towards formation of the quinonoidal bases. The values of the decay constants (kDMA and kDMA+FE), used to calculate the percentage of protection against the 1O2 ( Table 5), were obtained from exponential fits

for the first-order decay curves of DMA at 375 nm, in the presence and absence of jambolão FE at pH 1.0 and 3.0 conditions (data not shown). The proportion of functional extract used in these analyses (2.45%v/v) was equivalent to monomeric anthocyanin concentration of 2.1 μg/ml. The results obtained (about 60%

of protection at both pH conditions) corresponds Buparlisib chemical structure to an activity enough higher than those reported by Wang and Jiao (2000), where percentages of protection against the 1O2 between 8% (blueberry) and 15% (strawberry) were obtained when a juice proportion of 5%v/v was used. Regarding the ABTS + scavenging capacity, the TEAC value at pH 5 was 2.2–2.7 times higher when compared to TEAC values at pH 1.0 and 3.0 (Table 5). These results indicated that the colourless forms of anthocyanins tend to have a greater free radical scavenging capacity than the flavylium cation form. Since the TEAC values under pH 7.0 and 9.0 conditions were similar to the one obtained at pH 5.0, both hemiacetals/chalcones and quinonoidal base forms show similar ABTS + scavenging capacities. The increase in the free radical scavenging capacity of anthocyanins with increasing pH was due to the higher reducing capacity showed by the colourless (hemiacetals/chalcones) and quinonoidal base forms of anthocyanins as compared to the flavylium cation species (Vieyra et al., 2009). TEAC values obtained at pH 5.0–9.0 (9.7–12.7 μmol Trolox/g fruit) are in the same range as the ones reported for jambolão fruits (15 μmol Trolox/g fruit, unbuffered aqueous solution) (Luximon-Ramma et al., 2003).

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>