# Antioxidant and Antiglycation Properties of Seventeen Fruit Teas Obtained from One Manufacturer
## 1 Introduction  
Tea is currently one of the most popular beverages in the world [1; 2]. Every year, the consumption of teas, especially fruit teas, is increasing as a result of raised public awareness of their health-promoting properties. Fruit teas are a mixture of dried fruit, flowers, or leaves. Contrary to popular belief, these products do not contain black tea leaves. The addition of fruit juice concentrates and acidity regulators (e.g., citric acid) improves the taste and aroma of fruit teas [3]. Indeed, fruit tea infusions are successfully replacing sweetened drinks and juices. Interestingly, studies performed in the USA in the years 2011-2016 demonstrated that the highest tea consumption was observed in elderly people aged 51 to 70 years, non-Latin Asians, white people, and people with higher education and income [2]. This is not surprising, because tea has a number of health-promoting properties. One of them is strong antioxidant activity manifested by scavenging reactive oxygen species (ROS). Oxygen free radicals are atoms or molecules with one unpaired electron or more. They are most often formed under the influence of various physical factors, such as temperature, UV, and ionizing radiation, as well as xenobiotics (e.g., medicines, cigarette smoke, and air pollution) [4; 5; 6]. The situation in which the production of free radicals exceeds the body's ability to neutralize them is called oxidative stress (OS). It leads to oxidative damage to proteins, lipids, and DNA, which in turn disturbs cell metabolism and entails the development of cardiovascular [7], immunological [8], neurodegenerative [9; 10], and metabolic diseases [11; 12], as well as cancer [13; 14]. The human body is equipped with specialized antioxidant mechanisms (antioxidant enzymes: catalase, superoxide dismutase, and glutathione peroxidase; low molecular weight antioxidants: uric acid, glutathione, and albumin; and antioxidant vitamins: ascorbic acid and \(\alpha\)-Tocopherol) [5; 14]. In states with impaired antioxidant barrier and/or overproduction of ROS, the use of extrinsic antioxidants is recommended [8; 15]. Exogenous antioxidant compounds are widespread in plant material, animal tissues, and microorganisms. The most important sources of antioxidants are flavonoids, carotenoids, phytosterols, phenolic compounds, and vitamins C and E [16; 17; 18; 19]. They occur in particularly large quantities in black, red, and green teas, as well as herbal teas [3; 17; 20]. The antioxidant abilities of teas depend mainly on the composition of a given tea [3; 17; 20]. The total content of polyphenols and total antioxidant activity are higher in bearberry tea than in cranberry, mint, chamomile, and even green and black teas [21]. It is assumed that the antioxidant properties of teas may also be determined by the origin of tea ingredients [22]. Moreover, the antioxidant potential of teas of the same composition but obtained from another manufacturer may vary. This is most likely due to different cultivation methods, harvesting period, differences in agronomic procedures, fermentation time, and other treatments typical of the tea-making process of a given manufacturer [22; 23; 24]. Interestingly, antioxidant properties of teas also depend on the brewing method [16; 25]. It has been shown that the brewing temperature and time are extremely important in the process of phenolic component extraction [17; 23; 25]. Some studies have confirmed that elevated levels of polyphenic compounds of black, green, and white tea can be reached by extending the brewing time to more than ten minutes [25; 26; 27]. High antioxidant capacity is also demonstrated by herbal tea infusions, and this activity is correlated with the content of polyphenols in a given tea [22; 27; 28]. While much attention has been paid to traditional leaf teas, there have been few studies assessing the antioxidant properties of infusions made from dried fruit [20]. Moreover, there have been no studies comparing the antioxidant potential of fruit teas with respect to brewing temperature and time.