Enzymatically Extracted Apple Pectin Possesses Antioxidant and Antitumor Activity

Abstract

The biological activity of apple pectin extracted conventionally or enzymatically using endo-xylanase and endo-cellulase, was tested in vitro. The analyses were performerd in tetraplicates and the statistical significance of the differences were assessed using ANOVA, Tukey post hoc and LSD (the least significant difference) tests. Multivariate regression analysis was applied to determine the structural components that have a crucial importance for antioxidant and antitumor properties of pectins. The pectins extracted by enzymes contained up to four times more ferulic acid and showed twice as great ability to neutralize free radicals and Fe(III) reduction. The antiradical potential positively correlated with phenols, fucose and rhamnose content. In the assays performed on HT-29 human adenocarcinoma and B16F10 melanoma cell cultures, the "green" pectins, contrary to acid isolated ones, exhibited remarkable anti-neoplastic potential while being nontoxic to nontransformed L929 cell line. The pectins in the dose of 1 mg/mL were capable of inhibiting adhesion (max 23.1%), proliferation (max 40.4%), invasion (max 76.9%) and anchorage-independent growth (max 90%) of HT-29 cells (significance level p < 0.001). These pectin preparations were slightly less active towards B16F10 cells. The enzyme-isolated apple pectins may be useful as a functional food additive and an ingredient of the ointment formulas for post-surgical melanoma treatment.

Keywords: anticancer activity; antioxidant activity; enzymatic extraction; ferulic acid; pectin.

Figure 1

DPPH^•, ABTS^•+ and ^•OH scavenging activity and ferric-reducing power of apple pectins (in vitro tests). Data are presented as the mean ± SD of four independent experiments. P_cel—cellulase-extracted pectin; P_xyl—xylanase-extracted pectin; P_{cel + xyl}—pectin extracted with both cellulase and xylanase; P_commercial—commercial apple pectin.

Figure 2

The effect of apple pectins on HT-29 cell proliferation, migration, adhesion and growth in soft agar in vitro. The values represent the means ± SD of cells/colonies (% control). All the experiments were performed thrice in triplicate. * p ˂ 0.001 vs. the control group (Tukey test). P_cel—cellulase-extracted pectin; P_xyl—xylanase-extracted pectin; P_{cel + xyl}—pectin extracted with both cellulase and xylanase; P_commercial—commercial apple pectin.

Figure 3

The effect of apple pectins on B16F10 cell proliferation, migration, adhesion and growth in soft agar in vitro. The values represent the means ± SD of cells/colonies (% control). All the experiments were performed thrice in triplicate. * p ˂ 0.001 vs. the control group (Tukey test). P_cel—cellulase-extracted pectin; P_xyl—xylanase-extracted pectin; P_{cel + xyl}—pectin extracted with both cellulase and xylanase; P_commercial—commercial apple pectin.