Effects of extraction conditions on the chemical structure and biological activity of white cabbage pectin

The purpose of this study was to isolate and perform chemical analyzes as well as biological testing of pectic material from white cabbage isolated by sequential aqueous ionic solutions (SEQAIS) or a simple pure water extraction (PW). Water extraction was aimed at yielding water-soluble pectins only, while the harsher conditions in SEQAIS aimed at extracting proto pectin as well. The pectic material resulting from the various extraction steps was characterized and tested, in order to determine whether structural and biological activity were influenced through different isolation procedures. The SEQAIS fractions obtained were one water-soluble and six partly water-soluble extracts, whereas PW yielded two water-soluble extracts. Sugar composition analysis, linkage analysis, HPSEC molecular weight distribution, HPAEC and 13C NMR were run to obtain structural characteristics of the extracted material. Both extraction procedures resulted in degradation of pectin. Pectin containing highly methyl esterified GalpA probably underwent β-elimination due to neutral pH during PW, while hydrolysis of Araf occurred in the first step of SEQAIS in 50 mM acetic acid pH 4.5. Water-soluble extracts were tested for complement-fixing activity and acidic extracts with degraded side chains showed reduced activity. Authors suggest that extraction conditions at neutral pH should be used in order to withhold side chain structure and immuno-activity.