# Polypphenols: Natural Antioxidants to Be Used as a Quality Tool in Wine Authenticity
## 4 Current Analytical Approaches to Wine Authenticity
### Studies Focusing on Varietal or Geographical Origin Discrimination  
Chemotaxonomical studies employing polyphenolic compounds mainly focus on (intra-, inter-) varietal/geographical origin characterization, discrimination as well fraud detection. As the data provided by the analytical platforms do not often solely target polyphenolic compounds, in modern studies polyphenolic substances are part of the compounds that contribute to class separation. Most recently, [PERSON] et al. (2020) provided the characterization of the metabolome of 11 single-cultivar, single-vintage Italian red wines with the use of untargeted HRMS metabolomics. In this significant study, among other biomarkers, quercetin was found more abundant in Sangiovese wines followed by Nebiolo and Nerello, isorhamentin was more abundant in Nebiolo wines, while anthocyanin content was found higher in Teroldego wines [124]. Regarding grapes from the same variety, [PERSON] et al. (2016) reported that Nebiollo wine samples evidenced significant differences in grape anthocyanin profile in comparison to Uva Rara and Vespolina cv. varieties enabling their classification [141]. Several studies have been conducted worldwide contributing to wine authenticity assessment. Concerning Argentinian wines, [PERSON] et al. (2015) employing HRMS metabolomics reported that three malvidin-derived anthocyanins contributed significantly to the geographical and varietal discrimination of 27 wines samples [142]. [PERSON] et al. (2018) also employing HRMS metabolomics proposed a method based on the calculation of secondary metabolite indexes namely (dihydro-)flavonols and anthocyanin ratios, to identify the unauthorized use of Primitivo and Negro Amaro grapes in the production of Valpolicella wines. They showed that the addition of Primitivo in the blend could be detected as it increased the indexes related to Laricitrin, Delphinidin, and Petunidin. [143]. [PERSON] et al. (2016) reported that the abundance in the acylated glucoside of malvidin, as well as the ratios between the latter and the glucoside of malvidin along with the ratio between acylated and coumarilated monoglucosides of penoidin and malvidin were among the most significant variables, which enabled for varietal classification of 62 Romanian red wines. The same authors additionally reported that individual acylated and non-acylated anthocyanins as well as specific anthocyanin ratios contributed to vintage classification. Recently, [PERSON] et al. (2020) investigated the classification of 20 Polish red wines produced from Zweigelt (_Vitis vinifera_) and Rondo (non-Vitis vinifera) grape varieties based on the analysis of phenolic compounds by means of Ultra Performance Liquid Chromatography (UPLC) with a photo diode array detector (PDA) coupled to mass spectrometry. As expected, the non _Vitis vinifera_ cultivar exhibited higher concentrations of anthocyanin diglucosides while in the _V. vinifera_ variety the anthocyanin monoglucosides were found in greater abundance. An interesting finding of this study was that anthocyanin diglucosides were also found present even in low concentrations in the _V. vinifera_ Zweigelt grape variety [144]. The latter evidence is in agreement with a relatively recent work from [PERSON] et al. (2015) questioning earlier reports that denoted the absence of these compounds in _V. vinifera_ varieties [9; 19]. [PERSON] et al. (2020) employed proton-nuclear magnetic resonance instrumentation (\({}^{1}\)H-NMR) combined with multivariate statistical analysis to investigate the changes of metabolite levels in Cabernet Sauvignon, Merlot, and Cabernet Gernischt Chinese dry red wines. In this study, gallic acid was among the significant markers discriminating the grape varieties. [PERSON] et al. (2017) investigated the intra-varietal diversity of Aglianico _cv._ secondary metabolites including anthocyanins, flavonols, flavanols, and resveratrol, identifying significant differences among the accessions studied [145]. Reports on phenolic compounds mostly refer to red wines.