Iveta Uhliariková

Wild fruits are distributed worldwide, but are consumed mainly in developing countries, where they are an important part of the diet. Still, in many other countries, they are consumed only locally. Blackthorn (Prunus spinosa L.) is an underutilized species rich in fibres and phenolic compounds, making it suitable as a potential functional food for supporting human health. Cold (Cw) and hot (Hw) water-extracted (poly)phenolic polysaccharide–protein complexes, differing in carbohydrate, phenolic and protein contents, were isolated from blackthorn fruits and characterized. The complexes exhibited molecular weights of 235,200 g/mol (Cw) and 218,400 g/mol (Hw), and were rich in pectic polymers containing galacturonic acid, arabinose, galactose and rhamnose, indicating a dominance of homogalacturonan (HG) [→4)-α-D-GalA(1→4)-α-D-GalA(1→]n and a low content of RGI [→2)-α-L-Rha(1→4)-α-D-GalA(1→2)-α-L-Rha(1→]n sequences associated with arabinan or arabinogalactan. Minor content of glucan, probably starch-derived, was also solubilized. Pectic polysaccharides were highly esterified and partly acetylated. Pharmacological testing was performed in male Dunkin–Hartley guinea pigs, a model with human-like airway reflexes. Both complexes affected airway defense mechanisms. Particularly, Hw significantly suppressed citric acid-induced cough, similar to codeine, and reduced bronchoconstriction comparably to salbutamol in a dose-dependent manner. These findings support further exploration of Hw as a natural antitussive and bronchodilatory agent.

Although several therapeutic effects have been attributed to wild blackthorn fruits, their use is still negligible. Purification of the antioxidant-active fraction, obtained from wild blackthorn fruits by hot ammonium oxalate extraction (Ao), yielded seven fractions after successive elution with water, sodium chloride and sodium hydroxide solutions. The purified fractions differ in carbohydrates, proteins, and phenolics. About 60% of the applied Ao material was recovered from the column, with the highest yields eluted with 0.25 M NaCl solution, accounting for up to 70 wt% of all eluted material. Analyses have shown that two dominant fractions (3Fa and 3Fb) contain 72.8–81.1 wt% of galacturonic acids, indicating the prevalence of homogalacturonans (HG) with a low acetyl content and a high degree of esterification. The low content of rhamnose, arabinose and galactose residues in both fractions indicates the presence of RG-I associated with arabinogalactan. In terms of yield, the alkali-eluted fraction was also significant, as a dark brown-coloured material with a yield of ~15 wt% with the highest content of phenolic compounds of all fractions. However, it differs from other fractions in its powdery nature, which indicates a high content of salts that could not be removed by dialysis.