Autori: Eugenia Mazzara, Arianna Caprodossi, Ahmed Mustafa, Filippo Maggi e Giovanni Caprioli

Abstract
Sumac, Rhus coriaria L., is employed as a natural preservative in the food sector, due to its rich content of antioxidant compounds, including hydrolysable tannins, phenolic acids, anthocyanins, and flavonoids. In this work, the phytochemical characterization of sumac fruits from five Sicilian accessions was performed to evaluate their potential as a food preservative for nutraceutical exploitation. Spectrophotometric tests and HPLC-MS/MS analyses were conducted to assess and compare the antioxidant power of the water extracts produced with the five sumac accessions. Principal component analysis was also carried out to better visualize the obtained results. Flavonoids and phenolic acids, namely isoquercitrin (20,342.82 mg/kg dry extract) and gallic acid (197,489.19 mg/kg dry extract), were more abundant in fruits from the population of San Biagio Platani, while the one from Giarratana was characterized by a higher content of anthocyanins such as cyanidin-3-glucoside (20,889.81 mg/kg dry extract). These two populations can be recognized as the most suitable settings for the implementation of sumac cultivation and the development of sumac-based products, especially for food and nutraceutical purposes.
Keywords: sumac; Sicilian accessions; water extracts; HPLC-MS/MS; antioxidants; food supplements; nutraceuticals

1. Introduction
Rhus coriaria L. (Anacardiaceae), commonly known as sumac, is a 1–3 m high shrub or small tree possessing reddish or dark-brown, spherical, and fluffy drupe fruits, with dark-purplish glandular hairs, arranged in clusters, deriving from dense panicles. It can grow widely (between hedges, along roads, and up to 600–700 m a.s.l.), and it has been cultivated for several centuries in poor soils [1]. This species is diffused mainly in temperate and tropical regions, especially in Mediterranean, Middle Eastern, and Western Asian shores. It is employed as a flavoring spice and plant medicine, especially in Iran, Turkey, Palestine, Israel, and Jordan [2]. In the past, sumac has been used as a natural and traditional remedy, particularly in the treatment of diarrhea, liver disease [3], ulcer [4], hemorrhoids, animal bites, pain [5], dysentery, diuresis, hemorrhage, ophthalmia, conjunctivitis, and as a stomach tonic. Its use has also been indicated for cholesterol reduction, in the treatment of sore throat, and as an abortifacient [6]. Several biological properties have been reported for sumac, including the antibacterial [7], hepatoprotective [8], antifungal [9], antioxidant, anti-inflammatory [10], DNA-protective [11], anti-ischemic, vasorelaxant [12], antidiabetic [13], anticancer [14], and antinociceptive [15] effects. From an industrial point of view, R. coriaria is employed in the textile field as a tanning agent, especially for leather, and as a natural dye, with a high fixation, retention, and fungal resistance properties, being effective against wood decay [16]. Notably, sumac aqueous extract was shown to improve the quality of a Turkish fermented sausage [17] and to enhance the shelf life of rabbit meat [18], while the ethanolic extract possessed antimicrobial effects in minced meat [19], suggesting an important role of sumac as a natural preservative in the food industry. The numerous above-mentioned pharmacological activities and applications of sumac can be correlated with the presence of more than 200 biomolecules in the plant. Among them, the most important ones are hydrolysable tannins, phenolic acids, anthocyanins, and flavonol glycosides [20,21,22,23]. Recently, innovative extraction techniques based on deep eutectic solvents, ultrasounds, and microwaves [24] have been introduced for sumac to extract the aforementioned bioactive compounds. In this work, a phytochemical analysis of sumac fruits from different Sicilian populations was carried out to evaluate their phytonutrients as food preservatives and for nutraceutical purposes. More specifically, after a preliminary extraction optimization aimed at identifying the best extraction conditions, the antioxidant capacity and the content of bioactive compounds, especially phenolic acids and anthocyanins, were investigated in the fruit extracts from five Sicilian sumac populations, by means of spectrophotometric assays and HPLC-MS/MS analyses. The final objective of this study was to identify the most suitable locations in Sicily for implementing sumac cultivation and developing sumac-based products, especially for food and nutraceutical applications.

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