Abstract
Phenolic compounds were extracted from three wild grapevine species: Vitis californica, V. riparia and V. amurensis seeds using 80% methanol or 80% acetone. The total content of phenolic compounds was determined utilizing the Folin-Ciocalteu’s phenol reagent while the content of tannins was assayed with the vanillin and BSA precipitation methods. Additionally, the DPPH free radical scavenging activity and the reduction power of the extracts were measured. The RP-HPLC method was applied to identify the phenolic compounds in the extracts, such as phenolic acids and catechins. The seeds contained large amounts of tannins, catechins and gallic acid and observable quantities of p-coumaric acid. The total content of phenolic compounds and tannins was similar in the extracts from V. californica and V. riparia seeds. However, the total content of total phenolic compounds and tannins in the extracts from V. californica and V. riperia seeds were about two-fold higher than that in the extracts from V. amurensis seeds. Extracts from seeds of the American species (V. californica and V. riparia) contained similarly high concentrations of tannins, whereas extracts from seeds of V. amurensis had approximately half that amount of these compounds. The content of catechin and epicatechin was similar in all extracts. The highest DPPH• anti-radical scavenging activity was observed in the acetonic and methanolic extracts of V. californica and V. riparia seeds— while the acetonic extract from the V. californica seeds was the strongest reducing agent.
Highlights
The known species of grapevine have been divided into three groups based on their origin: Eurasian, American and East-Asian categories
V. riparia seeds displayed a high content of phenolic compounds, 396 and 377 mg/g of acetonic extract and 301 and 308 mg/g of methanolic extract, respectively
A similar trend was observed when the total content of phenolic compounds was analyzed in other calculations (Table 1)
Summary
The known species of grapevine have been divided into three groups based on their origin: Eurasian, American and East-Asian categories. The processing of grapes for wine and juice yields approximately 10 million tons of press residues which is composed of 38–52% seeds [1,2]. Grapevine seeds are a rich source of polyphenols, which are characterized by a variety of properties, such as antibacterial and antioxidant activities. Polyphenols are extracted from the grapevine seeds and passed to the wine [5]. Phenolics are largely responsible for a dietary anomaly known as the French paradox [6]. This term was coined following certain epidemiological discoveries, such as the low myocardial ischaemia mortality rate despite the elevated consumption of saturated lipids and cholesterol in France [5]. It is thought that the French paradox is a result of the relatively high consumption of red wines by the Mediterranean nations
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