# Biochemical Profile and Antioxidant Activity of Fresh Fruits from Apple Genotypes
## 1 Introduction  
Apples (_Malus domestica_) are among the most consumed and appreciated fruits globally due to their nutritional value and benefits for health. Widespread increasing consumption of apples, their juices, and derived products along with their rich phytochemical profile highlight their significant potential to positively influence human health [1]. The diversity of apple genotypes offers a wide range of biochemical characteristics, such as the content of polyphenols, flavonoids, vitamins, organic acids, and natural sugars, all of which contribute to the nutritional profile of the fruit [2, 3]. Apples contain phenolic compounds like flavonoids, phenolic acids, and tannins, which contribute to the fruit's antioxidant activity, neutralizing free radicals, protecting cells from oxidative stress, and reducing the risk of chronic conditions while enhancing its nutritional quality and providing health benefits [3, 4]. More than 60 phenolic compounds have been identified in apples. They are part of the plant's secondary metabolism and perform essential functions such as growth, defense against pathogens, color, and aroma. They are also vital for growth and reproduction and are mainly synthesized when the plant is submitted to stressful conditions such as infections, wounds, and ultraviolet radiation [5]. Phenolic compounds are organic compounds with at least one phenolic unit and two or more hydroxyl groups in the structure [5] and fall into two groups: flavonoids and non-flavonoids, the latter including phenolic acids, stilbenes, lignans, and tannins [5]. Apples contain six subclasses of flavonoids, namely flavanols, flavones, flavanones, monomeric and oligomeric flavanols, dihydrohalcones, and anthocyanins [5; 6; 7; 8]. Tannins are water-soluble polyphenolic substances capable of forming complexes with proteins, polysaccharides, nucleic acids, steroids, alkaloids, and saponins [9]. Depending on their chemical structure and properties, apples contain both hydrolysable and condensed tannins [10; 11]. Their complexity depends on the flavanol or flavandiol units, which vary among constituents and within sites for interflavan bond formation [12; 13]. The biochemical profile of apples varies significantly depending on the geographical area of cultivation due to the influence of multiple environmental factors, such as climate, soil type, altitude, and specific agricultural practices. Environmental conditions are essential factors in determining the content of bioactive compounds in fruits, such as polyphenols, flavonoids, vitamins, and minerals [4; 14]. The content of soluble sugars and organic acids in apples differs depending on the cultivar and can be influenced by factors such as light intensity, sun exposure, and other environmental conditions [15; 16]. At the same time, [PERSON] et al. [17] considered that the geographical area of cultivation plays an essential role in determining the resulting metabolite profiles. The antioxidant activity of apples is one of their main benefits, as it is associated with the prevention of chronic illnesses such as cardiovascular diseases, diabetes, and certain types of cancer. Among antioxidants, it has been estimated that the total content of phenolic compounds, flavonoids, anthocyanins, and ascorbic acid has a major contribution to the overall antioxidant activity of the fruit [18]. Furthermore, the variations between genotypes in terms of the concentration and composition of these compounds provide a valuable opportunity for the selection and improvement of apple varieties. Previous research has highlighted the differences between genotypes, emphasizing their influence and that of climate as the main factors determining metabolite profiles and fruit characteristics [19; 20]. In this context, this study aims to evaluate the biochemical profile and antioxidant activity of different apple genotypes to characterize genetic diversity and identify those with superior functional and nutritional potential.