Isolation, chemical characterization and antioxidant activity of Prunus spinosa L. fruit phenolic polysaccharide-proteins

Wild blackthorn fruits are a slightly explored area and their use is negligible, although they show many therapeutic effects. Polysaccharide complexes were solubilized from ripe Prunus spinosa L. fruits by sequential extraction with water (cold and hot), oxalate, ammonia, and sodium hydroxide solutions. The extracted fractions were rich in carbohydrates, phenolics, and proteins, indicating the presence of complexes of these compounds. It was found that most of the material was released with 5% KOH and hot water. The aqueous fractions had a high molecular weight and also polydispersity index, while the other fractions had low molecular weight. Based on the monosaccharide composition, three groups of fractions were observed. The aqueous and oxalate fractions represent highly esterified pectin material, ammonia extraction provided a mixture of de-esterified pectin and hemicelluloses, and alkaline isolates were rich in arabinogalactan and hemicelluloses. Antioxidant activity tests revealed significant effects of blackthorn samples, alkali-extracted fractions at concentrations of 0.02 and 0.05 mg/mL achieved DPPH radical scavenging comparable to that of vitamin C. Most samples achieved maximum activity comparable to vitamin C at a concentration of 0.1 mg/mL. An analogous effect was also found by the FRAP test, all fractions had a significant reducing capacity at a concentration of 0.05 mg/mL, but only the alkaline fractions reached almost vitamin C level. Preliminary results may support interest in these undiscovered natural fruits as a rich source of natural antioxidants.

Automated summary

The study found that wild blackthorn fruits are rich in polysaccharide complexes, including carbohydrates, phenolics, and proteins. Most of the material was released with 5% KOH and hot water. Based on the monosaccharide composition, the extracted fractions were divided into three groups, including highly esterified pectin material, a mixture of de-esterified pectin and hemicelluloses, and arabinogalactan and hemicelluloses. The blackthorn fruits exhibited significant antioxidant activity, especially the alkali-extracted fractions at concentrations of 0.02 and 0.05 mg/mL. Preliminary results suggest that blackthorn fruits may serve as an unexplored natural source of antioxidants.