INVESTIGATION OF THE ANTIOXIDANT CONTENT OF ISABELLA GRAPE (VITIS LABRUSCA L.)

4th INTERNATIONAL CONGRESS OF VETERINARY BIOCHEMISTRY AND CLINICAL BIOCHEMISTRY, Sivas, Türkiye, 4 - 07 Eylül 2025, ss.33-37, (Tam Metin Bildiri)

Objective: Isabella grape (Vitis labrusca L.) is a grape variety widely cultivated in the Black

Sea Region, notable for its high polyphenol content and bioactive compounds. There is an

inverse relationship between diets rich in antioxidants and the incidence of chronic diseases.

Bioactive compounds found in natural products help prevent these conditions by scavenging

reactive oxygen species responsible for disease incidence. This study aimed to investigate the

total phenolic and flavonoid contents as well as the antioxidant capacities of different extracts

obtained from the pulp and skin of Isabella grape.

Material and Methods: Mature Vitis labrusca grapes grown in Ankara were used in this

study. The pulp and skin portions of the grapes were extracted using water, methanol, and

ethanol as solvents. Each extraction was performed in triplicate, and DPPH radical

scavenging activity, total polyphenol, and flavonoid contents were analyzed

spectrophotometrically.

Results: The phenolic contents of grape skin in ethanolic, methanolic, and aqueous extracts

were found to be 2.42 ± 0.02 mg/g, 2.09 ± 0.18 mg/g, and 1.13 ± 0.10 mg/g, respectively;

whereas in the pulp they were 1.04 ± 0.20 mg/g, 0.55 ± 0.20 mg/g, and 0.35 ± 0.06 mg/g. The

flavonoid contents of grape pulp in ethanolic, methanolic, and aqueous extracts were 1.42 ±

0.29 mg/g, 0.86 ± 0.17 mg/g, and 0.37 ± 0.15 mg/g, respectively; while in the skin they were

3.54 ± 0.29 mg/g, 2.98 ± 0.23 mg/g, and 1.18 ± 0.08 mg/g. DPPH radical scavenging activity

for grape pulp in ethanolic, methanolic, and aqueous extracts was 345.87 ± 92.83 µg/g,

204.93 ± 28.71 µg/g, and 100.78 ± 15.90 µg/g, respectively; and for the skin, 692.46 ± 32.94

µg/g, 559.93 ± 21.30 µg/g, and 283.09 ± 33.11 µg/g. It was determined that the grape skin

exhibited higher total phenolic content and antioxidant activity, with the ethanolic extract

showing the strongest radical scavenging capacity.

Conclusion: Vitis labrusca possesses strong antioxidant properties, particularly due to the

polyphenolic compounds concentrated in its skin. It may play a supportive role as a functional

food in the prevention of chronic diseases associated with oxidative stress. Considering the

notably high antioxidant potential of V. labrusca, further studies are needed to analyze its

phenolic components and to evaluate the effects of its ethanolic extracts in experimental

animal models.