# Portuguese Grapevine Leaves: A Neglected By-Product with High Potential
## 2 Chemical Composition of Portuguese Grapevine Leaves
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Compound/Formula** & **Concentration** & **Toxicity** & **Bioactivity** \\ \hline Chlorophyll & 198.53–318.29 \(\mathrm{\SIUnitSymbolMicro g}\)/g [77] & Nontoxic [148] & Antioxidant, anti-inflammatory, anticancer, and anti-obesity [136] \\ \hline Pheophytin & 6.45 \(\times\) 10\({}^{-24}\)– 57.96 \(\mathrm{\SIUnitSymbolMicro g}\)/g [77] & Nontoxic [144; 149] & Anti-hepatitis C [145], antioxidant [150], anti-inflammatory [151], antimicrobial [142], antihypercholesterolemic [144], and anticancer [149] \\ \hline Auroxanthin & 34.16–61.48 \(\mathrm{\SIUnitSymbolMicro g}\)/g [77] & None found & Antioxidant [134] \\ \hline Antheraxanthin & 10.61–26.56 \(\mathrm{\SIUnitSymbolMicro g}\)/g & None found & Antioxidant [152] \\ \hline _trans_-lutein & 10.32–25.83 \(\mathrm{\SIUnitSymbolMicro g}\)/g & Nontoxic [153] & Anti-inflammatory, anticancer [154], antioxidant [155] \\ \hline \hline \(\beta\)-carotene & 7.10–20.38 \(\mathrm{\SIUnitSymbolMicro g}\)/g & Nontoxic [156] & Antioxidant [150], vitamin A precursor [157], anti-inflammatory [137; 139], antimicrobial [143], prevention and treatment of obesity [158] \\ \hline Neoxanthin & 5.50–22.10 \(\mathrm{\SIUnitSymbolMicro g}\)/g & None found & Antioxidant [159], anticancer, and chemopre preventive [141] \\ \hline Violaxanthin & 11.56–30.39 \(\mathrm{\SIUnitSymbolMicro g}\)/g & None found & Antioxidant [135], anti-inflammatory [140; 160], anticancer, and antiproliferative [140] \\ \hline Zeaxanthin & 11.42–8.17 \(\mathrm{\SIUnitSymbolMicro g}\)/g & Low acute toxicity & Antioxidant [135], anti-inflammatory, anticancer [146; 154], and \\ C\({}_{40}\)H\({}_{56}\)O\({}_{2}\) & [77] & Mouse LD50: \(>\)8000 mg/kg of body weight & Antioxidant [146; 154], and \\  & & Mouse LD50: \(>\)8000 mg/kg of body weight [161] & neuroprotective [146] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Pigments identified in Portuguese grapevine leaves of red cultivars Bastardo, Trincadeira, Tinta Barroca, and Castelão. not been characterized, and it is presumed that, because they occur in trace amounts, the toxicity of consuming these molecules is low. In summary, autochthonous grape varieties such as Touriga Nacional, Trincadeira, and Baga possess a rich profile of bioactive compounds, including flavonoids (e.g., quercetin and kaempfer) and hydroxycinnamic acids, similar to those found in the leaves of other cultivars and regions [31; 43]. These compounds are present in higher concentrations in Portuguese varieties, as highlighted in our study, but are also found in grape leaves from other countries, such as Turkey, Tunisia, and Brazil. The primary fatty acids identified in Portuguese vine leaves were palmitic, linoleic, and linoleic [77], as has been reported for leaves from other regions [174]. As mentioned for the Portuguese cultivars studied, the leaves of the vine contain terpenoids and their derivatives, such as linalool, geranyl acetone, citral, limonene, among others [123], which is in alignment with a study carried out with leaves of Italian cultivars [175]. As for pigments, this study showed that chlorophylls exist in the highest concentration [77], a result also observed in grape leaves cultivated in Croatia [176]. Despite these similarities, it is important to note that the unique climatic conditions, diverse soils, and traditional viticultural practices of Portugal likely influence the distinct phytochemical composition of its grapevine leaves.