Phenolic Compounds from the Leaves of Vitis labrusca and Vitis vinifera L. as a Source of Waste Byproducts: Development and Validation of LC Method and Antichemotactic Activity

The cultivation of Vitis (Vitaceae) grape varieties is one of the most important economic activities in agribusiness in southern Brazil. Vitis varieties are rich in polyphenolic compounds with several pharmacological and biological activities, such as antioxidant action. In this context, this study analyzed qualitatively and quantitatively the anthocyans and flavonoids found in the leaves of grape varieties Vitis vinifera and Vitis labrusca. For this purpose, vine leaf extracts were prepared and the chemical profile of each was characterized by LC/MS-MS. Two high performance liquid chromatography-validated methods were performed using UV/VIS-LC-DAD detector to quantify phenolic compounds. The main anthocyanins isolated from vine leaves were cyanidin-3-O-glucoside and peonidin-3-O-glucoside. The flavonoids identified were rutin, quercetin-3-O-galactoside, quercetin-3-O-glucoside, and quercetin-3-O-glucuronide, which was the predominant compound. The Waters X-Terra® RP18 column allowed the effective separation of quercetin-3-O-glucuronide from the other flavonoids for the first time, besides the partial separation of quercetin-3-O-galactoside from quercetin-3-O-glucoside. Furthermore, another phenolic compound was confirmed by MS spectrometry, using direct infusion, as being trans-caftaric acid. The present study also investigates the antichemotactic activity in vitro of grape crude extracts, fractions, and isolated compounds. It was demonstrated that almost all fractions and isolated compounds showed increased antichemotactic effect in response to LPS with a more pronounced values of IC₅₀ for anthocyanins fraction, rutin, quercetin-3-O-galactoside, and trans-caftaric acid (0.9, 1.6, 3.7, and 5.1 ng/mL, respectively).