Effects of spraying over apple trees (Malus domestica; ‘Topaz’) with methyl salicylic acid (MeSA) and SA during fruit maturation were investigated for quality parameters (weight, firmness, hue angle, red blush, yield) and phenolic profile of the peel and pulp (HPLC–mass spectrometry). These treatment effects were also investigated for activities of the phenylpropanoid pathway enzymes phenylalanine ammonia-lyase, chalcone synthase and isomerase (combined), and flavanone-3β-hydroxylase. The MeSA and SA treatments resulted in poor fruit peel coloration, with higher hue angles and 20% and 10% lower red blush, respectively. Anthocyanin levels were also significantly lower (56%) for MeSA treatment. MeSA stimulated activities of phenylalanine ammonia-lyase and chalcone synthase/isomerase, which resulted in higher levels of flavanols (to 34%), flavonols (to 33%), and hydroxycinnamic acids (to 29%), versus control. Therefore, while these salicylate treatments improve levels of some beneficial polyphenols, they also have negative effects on the external quality characteristics of the fruit.

Key Message: The best yields in the extraction of hydroxycinnamic acids, flavanols and total phenolics from black cherry flowers were obtained with 40% ethanol and the poorest with water. A 30% higher content of total phenolics was obtained from leaves by using methanol rather than water. Context: Black cherry (Prunus serotina Erhr.) is widespread in Europe. Because it is an invasive species, most research has been aimed at trying to find a method to remove this shrub from forests. The incentive for the development of the research was that we were trying to find a possible folk use of black cherry leaves and flowers. Aims: The aim of this work was to study the detailed phenolic profile of extracts of P. serotina leaves and flowers. Methods: Three types of extracts of P. serotina were made. The extracts were analysed for differences in phenolics content based on different extraction methods. HPLC-MSⁿ was used to identify the phenolic compounds, and HPLC–DAD was used for their quantification. Results: The results show that different extraction methods result in differences in the amount of extractables. Flavanols are the main group of identified compounds in both leaves and flowers. A larger extraction efficiency leads to a higher amount of phenolics in the flowers compared to leaves (49.8 vs. 36.5 g/kg dry weight). No difference was detected in the amount of phenolics between water extracts of leaves and flowers. Each extract can be considered rich in phenolics. Conclusion: This work shows that leaves and flowers of P. serotina are a rich source of phenolic compounds. We provide interesting results that might be of interest in the industrial valuation of several compounds.

The content of sugars, organic acids, phenolic compounds and selected enzyme activities in the anthocyanin pathway were analyzed in NIGRA (Sambucus nigra var. nigra—black fruits) and VIRIDIS (S. nigra var. viridis—green fruits) fruits over four stages of ripening. The share of glucose and fructose in green fruits was higher than in colored fruits, and the sugar content increased significantly until the third developmental stage. Ripe NIGRA berries had 47% flavonol glycosides, 34% anthocyanins, 3% hydroxycinnamic acids and 14% flavanols, whereas the major phenolic group in the VIRIDIS fruits, making up 88% of the total analyzed polyphenols, was flavonols. NIGRA fruits were rich in anthocyanins (6020 µg g⁻¹ FW), showing strong activation of the late anthocyanin pathway (dihydroflavonol 4-reductase, anthocyanidin synthase). In both color types, phenylalanine ammonia lyase and chalcone synthase/chalcone isomerase activities were highest in the first stage and decreased during ripening. In VIRIDIS fruit, no anthocyanins and only one flavanol (procyanidin dimer) were found. This was most likely caused by a lack of induction of the late anthocyanin pathway in the last period of fruit ripening. The VIRIDIS genotype may be useful in studying the regulatory structures of anthocyanin biosynthesis and the contribution of distinct flavonoid classes to the health benefits of elderberries.

The brown marmorated stink bug (BMSB; Halyomorpha halys Stål.) is a highly destructive and polyphagous invasive pest that poses a serious threat to more than a hundred reported host plants. In the current study, the metabolic response of peach fruit of two cultivars—‘Maria Marta’ and ‘Redhaven’—to BMSB infestation was studied using high-performance liquid chromatography (HPLC) and mass spectrometry (MS). In general, a strong phenolic response to BMSB infestation in peach flesh in the injury zone was observed, with flavanol content increasing by 2.4-fold, hydroxycinnamic acid content by 5.0-fold, flavonol content by 3.2-fold, flavanone content by 11.3-fold, and dihydrochalcones content by 3.2-fold compared with the undamaged tissue in the cultivar ‘Maria Marta’. The phenolic response in the ‘Redhaven’ cultivar was even stronger. Consequently, the total phenolic content in the injured flesh also increased, 3.3-fold in ‘Maria Marta’ and 6.9-fold in ‘Redhaven’, compared with the uninjured flesh. Infestation with BMSB induced the synthesis of cyanidin-3-glucoside, which is not normally present in peach flesh. In comparison, the phenolic response was lower in peach peel, especially in the cultivar ‘Maria Marta’. The study showed that both peach cultivars reacted to BMSB infestation with an increase in phenolic content in the peach flesh, but in a limited area of injury.