Chemical and biological studies of fruit extracts from different Italian varieties of Prunus domestica L. (Rosaceae)

Prunus domestica L. (Rosaceae), also known as European plum, is a very ancient tree that has been discovered near the Caspian Sea about 2000 years ago. Nowadays, P. domestica is one of the most important species for its fruit market reaching more than 10 million tons a year in the word [1]. The plums are drupaceous fruits that are consumed fresh, canned or dried (prunes), as well as for jam, jelly, and juice production. Recently, the plum production has been increased due to the growing interest in the health benefits related with phytochemical content, predominated by flavonoids and phenolic acids showing antioxidant properties and potential activity in the prevention of cancer and chronic diseases [2]. Therefore, as the plums are considered promising healthy agents, the aim of the present work was the chemical and biological investigation of some typical Italian P. domestica varieties through comparison with the commercial variety Sangue di Drago. The fruits of varieties Rossa Casa Velasco (RCV), Formosa (F), Rusticano (R), and Sangue di Drago (SD) were selected and collected at the ripening stage. Then, fresh fruits were extracted with ethanol-water (70% v/v) by dynamic maceration for three consecutive days at room temperature, changing the solvent every 24 h. The dried extracts were firstly screened for the determination of their polyphenolic content and successively their chemical composition was investigated by means of ultra-high performance liquid chromatography coupled to a high resolution Orbitrap-based mass spectrometer equipped by an electrospray ionization source (UHPLC-HR-ESI-Orbitrap/MS). Results evidenced that among the extracts, RCV has the highest content of polyphenols (110.28 gallic acid equivalent/g of extract). The UHPLC-MS analyses showed the presence of hydroxycinnamic acids, with chlorogenic acid the most represented, flavonol glycosides, mainly quercetin derivatives, and procyanidins. Interestingly, some components are more expressed in the local varieties rather than in the commercial one. Among anthocyanins, cyanidin, petunidin, and delphinidin derivatives were found with delphinidin glucoside the most represented, especially in the RCV variety. Successively, the biological activity of the extracts, evaluating their in vivo effects on angiogenesis using the chick embryo chorioallantoic membrane (CAM) model, was explored. The extracts were also investigated for their in vitro activities by DPPH and ABTS scavenging, ferric reducing (FRAP), and denaturation of bovine serum albumin (BSA). Results showed that all the extracts exhibited a significant antiangiogenic response inducing a marked reduction of the microvasculature in the CAMs (34.44-50.55% of inhibition at 100 and 200 µg/egg) as compared to control. Regarding the antioxidant properties, the extracts showed a strong concentration-dependent activity. Interestingly, RCV has the most notable efficacy in all the antioxidant assays. Furthermore, the extracts demonstrated a promising anti-inflammatory activity (96.01-98.73% of inhibition at 500 µg/mL) due to their high protective effects on thermally induced denaturation of BSA. In conclusion, the plum extracts here presented can be considered a source of potential nutraceutical agents or functional food components that could reduce the risks of oxidative stress-related disorders.