## 3 Results and Discussion
### Bioactive Compounds and Antioxidant Activity
Specifically, the most abundant phenolic compounds found in K were quercetin-3-O-galactoside (473 \(\pm\) 7 mg/1000 g db), ferulic acid (23 \(\pm\) 2 mg/1000 g db), and epicatechin (5.4 \(\pm\) 0.9 mg/1000 g db) and in S, they were pelargonidin-3-glucoside (1139 \(\pm\) 24 mg/1000 g db), ellagic acid (530 \(\pm\) 17 mg/1000 g db), and quercetin-3-glucoside (436 \(\pm\) 33 mg/1000 g db). Generally, the phenolic quantities obtained are in accordance with those described in other studies [24; 36]. As described for TP, freeze-dried fruit extracts showed higher concentrations of these components than fresh fruits (\(p<0.05\)). Particularly, phenolics increased by \(\approx\)35% for kiwifruit and 21-28% for strawberry in relation to fresh samples (Equation (1)). Concerning the kiwifruit phenolic composition, [PERSON] et al. (2018) [37] established the significance of certain phenolic compounds in kiwifruit methanolic extracts as antioxidants. According to their study, the sequence of the phenolic components that contribute to reducing power is as follows: epicatechin \(>\) vanillic acid \(>\)\(p\)-coumaric acid \(>\) ferulic acid \(>\) syringe acid \(>\) caffeic acid \(>\) catechchin. The chemical antioxidant activity of kiwifruit measured in vitro is mainly due to compounds such as phenolic acids and flavonoids which can easily donate electrons by virtue of their aromatic structures [37]. Among the major phenolic components of kiwifruit, quercetin has been reported as a potent antioxidant with radioprotective abilities [38]. Additionally, ferulic acid has been shown to be a powerful antioxidant capable of scavenging hydroxyl and peroxyl radicals as well as nitric oxide radicals. It was revealed that ferulic acid pre-treatment significantly reduced the inflammatory response associated with ionising radiation in murine models [38]. Onthe other hand, strawberries are also considered a rich source of polyphenols, among them, anthocyanins are quantitatively the most significant ones [20]. Kiwifruits and strawberries may also be highlighted as important sources of VC [20; 31]. Along with polyphenic compounds, VC is considered the most significant water-soluble antioxidant and it intervenes in many physiological reactions. It is effective in scavenging superoxide radical anions, hydrogen peroxide, hydroxyl radicals, singlet oxygen, and reactive nitrogen oxide [35]. The physiological and biochemical effects of VC are a result of its role as an electron donor. Specifically, AA donates two electrons from a double bond between the second and third carbons of the 6-C molecule. In the present study, VC values of K were higher than those of S (Table 1). Some authors reported that the VC in kiwifruit is higher than other fruits such as oranges, strawberries, lemons, apples, peaches, or grapes [39]. In this case, freeze-drying caused significant losses (\(p<0.05\)) of VC by 10.31% and 6.63% in KD and SD, respectively, compared to fresh fruit (Equation (1)). When evaluating the VC content, it is important to consider that the molecule is very labile, thermosensitive, and easily oxidisable, and thus it is easily degraded [40]. In this sense, the freeze-dried sample's increased porosity makes VC more exposed to oxygen, which could adversely affect its stability [34]. Amounts of VC in KD and SD found in this study were comparable to those described by [PERSON] et al. (2016) [41] and [PERSON] et al. (2018) [42], respectively. The AOP of fruits is crucial for determining their functional value. Over the last few decades, fruit antioxidants have attracted growing interest, suggesting that their consumption may help prevent and reduce oxidative reactions that adversely affect human health, contributing to the development of chronic diseases and cancers in various ways. Since the AOP is due to synergistic reactions between different compounds, using more than one method to measure this activity correctly is recommended.