# From Vine to Wine: Coloured Phenolics as Fingerprints
## 1 Introduction  
Phenolic compounds are secondary metabolites produced by plants, many of which have been identified as bioactive substances with recognized antioxidant properties, which implies a high potential for applications in the health field [1]. Their natural occurrence has been used for statistical differentiation in food products, according to cultivar in plants [2] or bee pollen [3], as well as according to geographical origin in olive oil [4] or tomato derivatives [5]. Anthocyanins are a class of phenolic compounds classified as pigments and responsible for the red, purple, and blue colours in many fruits and vegetables [6]. In grapevines(_Vitis vinifera_), anthocyanins are predominantly located in the berry skins and play a crucial role for determining the colour and quality of red wines. These compounds contribute to the sensory attributes of red wines including hue, intensity, and colour stability [7]. The biosynthesis of anthocyanins in grape berries involves the flavonoid pathway, originating from the amino acid phenylalanine through the action of phenylalanine ammonia-lyase [6]. Key enzymes in this pathway include chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, dihydroflavonol 4-reductase, anthocyanin synthase, and uridine diphosphate-glucose flavonoid 3-o-glucosyltransferaseterase (UFGT) [8]. The final glycosylation step catalysed by UFGT is essential for anthocyanin stability and accumulation in grape skins [9]. Anthocyanin composition in grapes is influenced by genetic factors, environmental conditions, and viticultural practices [10]. Different grape varieties exhibit distinct anthocyanin profiles, characterized by variations in the types and proportions of anthocyanin derivatives such as malvidin, delphinidin, cyanidin, peonidin, and petunidin glucosides [11]. Environmental factors like temperature, light exposure, soil composition, and water availability can significantly affect synthesis and accumulation of anthocyanins [12]. Excessively high temperatures generally lead to pigment degradation [13]. An increased solar radiation (light exposure) enhances anthocyanin biosynthesis, whereas excessive shading can reduce their concentration in grape skins [14]. Similarly, moderate water deficit conditions have been associated with increased anthocyanin content due to the activation of stress-related metabolic pathways [15]. In winemaking, the anthocyanin extraction from grape skins into the must is a critical process that determines the colour intensity and hue of the resulting wine. Winemaking techniques such as maceration time, fermentation temperature, and the use of enzymes can have an influence on anthocyanin extraction and stability [7]. Additionally, anthocyanins can undergo various reactions during wine aging, leading to the formation of more stable pigments like polymeric anthocyanins, which contribute to the long-term colour stability of red wines [16]. There is an increasing need for wine authentication in the market, driving research to propose more effective chemical markers. The Canary Islands wine sector represents an essential economic activity, contributing to local development through employment and tourism. However, like many wine-producing regions, it faces challenges related to authenticity and fraud, which can compromise consumer trust and the value of its Denominations of Origin (DOs). Ensuring wine authenticity through reliable analytical methods is crucial for safeguarding their identity. Authentication strategies, such as anthocyanin profiling, provide a robust tool for verifying wine origin and strengthening quality control systems, ultimately benefiting both producers and consumers. Phenolic profiles [17] have been particularly used for differentiating wines based on grape cultivars and regions of origin. Advanced analytical techniques, such as mass spectrometry [18] or nuclear magnetic resonance [19], have been employed for phenolic analysis.