Isolation, Phytochemical Characterization, and Biological Activities of Fractions from Viscum album L. Berries Harvested from Populus nigra L.

Despite the recognized medicinal value of mistletoe, its berries remain relatively poorly characterized in terms of their phytochemical composition and biological properties. This study evaluated the phytochemical profile and the antioxidant, antidiabetic, and angiotensin-converting enzyme (ACE) inhibitory activities of the methanolic extract and its fractions from Viscum album L. berries harvested from Populus nigra L. Fractions F41–44 and F45–49 showed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) radical scavenging (IC50 = 1.36 and 0.39 mg/mL vs. 8.09 and 1.31 mg/mL for the crude extract) and α-amylase inhibition (7.37 vs. 2.55 mg acarbose equivalents/g). The highest oxygen radical absorbance capacity (ORAC) was found for F27–31 (250.79 vs. 135.66 mg Trolox equivalents/g), and the strongest ACE inhibition for F32–40 (IC50 = 1.98 vs. 3.83 mg/mL). The most active fractions were rich in chlorogenic acid, apigenin, taxifolin, quercetin, 3-O-methylquercetin, rhamnazin, isoquercetin, and isokaempferide, which correlated significantly with radical scavenging activity. Triterpenes, including ursolic, oleanolic, and betulinic acids, lupeol, betulin, and erythrodiol, were also detected. These findings provide new insights into the phytochemical composition and biological potential of mistletoe berries, supporting further research into their nutraceutical and phytopharmaceutical applications targeting oxidative stress, diabetes, and cardiovascular diseases.