Ecosystem Services of Blackthorn: Effects of Harvesting Time on the Functional Extraction of Polyphenolic Compounds and Antioxidant Activity

Abstract The objective of this study was to examine the potential ecosystem services of Blackthorn (Prunus spinosa L.) in view of its traditional importance as a source of food and medicine. Fruits were sampled from a suburban population in the southwestern part of Belgrade at three time points: after ripening in late summer, in early winter, and in early spring. Using spectrophotometric methods and ethanol and distilled water as solvents, the contents of polyphenolic compounds and the antioxidant capacity were determined. To assess the influence of the harvesting period, the results were analysed using descriptive statistics, one-way ANOVA, Tukey’s HSD and LS Means tests, Spearman’s correlation coefficient, and confidence interval models. The biochemical composition of the fruits was shown to depend on the time of harvest, as confirmed by the statistically significant differences between the sampling periods for all the parameters except anthocyanins. In all the sampling periods, the ethanolic extracts exhibited higher values of polyphenolic compounds and antioxidant capacity compared to the aqueous extracts. Early spring and early winter were identified as the most suitable harvesting times, as the strongest antioxidant activity measured by the FRAP test was recorded in the third period, and by the DPPH and ABTS tests in the second period. This study makes a significant contribution by confirming that the harvest time does not affect the anthocyanin content, thus highlighting the commercial potential of Blackthorn fruits as natural colourants based on anthocyanins. The patterns of variability suggest optimal harvesting times for the efficient extraction of bioactive compounds and the use of Blackthorn fruits in the development of functional foods and pharmaceutical products. Furthermore, the findings serve as a basis for developing strategies aligned with climate change predictions, as the results confirm a positive influence of low air temperatures preceding the second and third sampling on the bioactive components of the fruits.