# Study of the Phenolic Compound Profile of _Arbutus unedo_ L.
## 1 Introduction  
_Arbutus unedo_ L., also known as the strawberry tree, is a widespread evergreen shrub native to the Mediterranean region and North Africa, belonging to the Ericaceae family. Its fruits are a dark red drupe or berry with a spherical shape of approximately 2 cm in diameter and that is only tasty in late autumn when they are fully ripe. Traditionally, the consumption of fresh strawberry tree berries has been rare, and instead they are commonly used for the production of alcoholic beverages, such as wines, liqueurs, and brandies, or for the elaboration of prepared foods, such as jellies, compotes, and jams [1; 2; 3]. These wild berries have excellent nutritional value [4; 5; 6; 7] and are rich in bioactive components like phenolic compounds (PC), vitamins, and carotenoids, which are directly related to many beneficial health effects thanks to their high antioxidant capacity [5; 8; 9]. In fact, the leaves and berries of _A. unedo_ L. are used in natural medicine as antiseptics, diuretics, and laxatives [2; 10; 11], as well as in the treatment of cardiovascular diseases, such as hypertension, arteriosclerosis, and thrombosis [12; 13; 14]. These pharmacological effects can be associated with the bioactive compounds previously mentioned, mainly the PC. Plant PC are a wide group of secondary metabolites and common constituents of fruits and vegetables, which are considered an important class of antioxidant natural substances [15; 16; 17]. Their potent antioxidant capacity gives them a wide range of pharmacological properties, including anti-inflammatory, antiallergic, antibacterial, and anticanceractivities [18; 19]. In addition, they also reduce the risk of diseases mediated by oxidative stress, such as cardiovascular disease [20; 21]. There are many families and types of PC. The flavonoid family (flavones, flavonoids, flavanols, flavanones, anthocyanins, and isoflav) is the most common and widely distributed [22]. In a characterization study of PC in wild fruits, it was stated that catechin was the most abundant compound in _A. unedo_ L., which also presented the highest concentration of flavanols in comparison to the rest of the wild fruits analyzed, such as blackthorn, among others [23]. Some flavonoids, such as quercetin and myricetin, have also been quantified in these fruits [2]. Anthocyanins have also been described in the phenolic composition of the strawberry tree fruits. Indeed, they play a fundamental role, since they provide the characteristic red color of the berries, as well as high antioxidant activity [24]. Regarding phenolic acids, some of them, such as gallic, protocatechuric, p-hydroxybenzoic and vanillic, among others, have also been identified in the strawberry tree fruits [4]. Furthermore, the strawberry tree berry is one of the richest fruits in PC with high antioxidant activity, as demonstrated by [PERSON] et al. [25]. However, the chemical composition and antioxidant activity of strawberry tree fruits is highly influenced by the ripening stage and the environmental and climatic conditions. In this sense, [PERSON] et al. studied the influence of the ripening stage on the chemical composition and antioxidant activity of the strawberry tree berry by using spectrophotometric methods [26]. They observed that the total PC (TPC) was higher in the unripe and intermediate stages of ripeness. On the other hand, [PERSON] et al. provided original data on the nutritional value of wild strawberry tree fruits, studying the variation of some nutritional parameters and the changes in the concentration of some bioactive compounds of fruits harvested in different years from two different Spanish areas [27]. Nevertheless, these works have a limited number of analyzed samples and/or compounds, and no data have been published about the variation of the PC profile determined by HPLC-MS/MS to date.