## 1 Introduction  
Diabetes mellitus, a common metabolic disorder characterised by hyperglycemia, is a major health problem worldwide [1]. While traditional pharmacological interventions are effective, they often come with associated side effects and long-term considerations [2]. Consequently, there has been a growing inclination towards the investigation of natural compounds from plant sources, driven by the quest for safer and more holistic alternatives [3]. Among these, bilberry (_Vaccinium myrtillus_) (VM) and linguonberry (_Vaccinium vitistidae_) (VV) have emerged as promising candidates, exhibiting a rich composition of bioactive compounds that can contribute to antiradical properties, which are expressed in an antioxidant and antiradical manner [4; 5]. Furthermore, the research claims to explore the antiradical properties (which are considered antioxidants) of VM and VV, with a specific focus on the leaf and the aerial part extracts [6]. Understanding the impact of these natural extracts on management could offer novel insights and contribute to the development of complementary or alternative strategies for individuals affected by T2 DM [7]. Understanding the \(\alpha\)-amylase inhibition activity in VM is important for people with T2 DM because \(\alpha\)-amylase is an enzyme that helps break down complex carbohydrates into simpler sugars. In the human body, \(\alpha\)-amylase is produced in the pancreas and salivary glands [8]. Certain natural compounds found in foods, including plant extracts, may have \(\alpha\)-amylase inhibition activity [9]. Finding such inhibitory effects in VM and VV extracts could potentially slow down the digestion of carbohydrates, resulting in a slower release of glucose into the bloodstream [10]. This could be beneficial for individuals with T2 DM by helping to manage blood sugar levels [11]. Plant-based products (from leaves, stems, roots, fruits, etc.) can serve as supplements or substitute synthetic medications in the treatment of diabetes, offering the advantage of minimally proven side effects and the potential cost-savings in the management of the condition [12]. Furthermore, a study using VM leaves in rats with T2 DM demonstrated a beneficial effect on sugar levels. According to the research on VM leaf infusion, plasma glucose levels decreased by approximately 26% in two distinct stages of diabetes. The treatment also led to a 39% reduction in plasma triglyceride levels [13]. Interestingly, few articles have appeared in the past decade investigating the composition and pharmacological effects of VM leaves because previous studies have predominantly focused on the fruit aspect [11]. This study on two types of extracts from dry plant material generated new scientific data by identifying compounds in the leaves and stems of VM and VV, which had been the subject of limited prior research. The leaves and the aerial parts of VM and VV constitute the primary by-products. Studies [14; 15] have highlighted a significantly higher concentration of phenolic compounds in the leaves and stems of _Vaccinium_ species compared to berries; however, the research findings suggest that very little is known about the tannin and derivate content of the aerial part. For example, VM leaves usually have a high number of tannins, typically between 0.8% and 6.7% [11], whereas VV leaves contain a high level of tannins [16]. Tannins are natural compounds found in different plant tissues, particularly fruits, seeds, bark, leaves, and wood [17]. Tannins are polymeric molecules [18]. They belong to a group of polyphenic compounds and are known for their asringent taste [19]. A study looked at how adding tannin to diabetic rats on a high-fat diet affected their ability to resist oxidative damage. The findings showed that adding tannin to diabetic rats for 30 days had an antioxidant effect, lowering oxidative stress [20]. Another study describes the effects of tannins from Spondias Mombin on body and organ weight, serum amylase levels, and diabetes in streptozotocin-induced diabetic rats.