Bioactive Compounds in Cornus mas L. and Juniperus communis L.

The growing interest in plant-derived bioactive compounds has intensified research on traditional but underexplored species as potential sources of health-promoting metabolites. This study aimed to compare the phytochemical profiles and antioxidant potential of fruits of Cornus mas L. (Cornelian cherry) and Juniperus communis L. (common juniper) collected from two natural locations in Poland. Lyophilized fruits were subjected to combined alkaline and acid hydrolysis followed by extraction, and the released phenolic compounds were identified and quantified using UPLC–PDA. Total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin carotenoid content, chlorophylls, organic acids, and antioxidant activity (ABTS•+ assay) were determined spectrophotometrically. The fruits of C. mas exhibited significantly higher TPC (3584–3641 mg GAE/100 g d.m.), TFC (875–895 mg RUTE/100 g d.m.), TAC (247–266 mg CAE/100 g d.m.), and antioxidant activity (1544–1698 µmol Trolox/kg d.m.) compared with J. communis. Chlorogenic acid and quercetin were the dominant phenolic constituents in C. mas, whereas J. communis was characterized by higher proportions of protocatechuic acid, catechin, and kaempferol. J. communis fruits contained higher total organic acids, mainly citric acid, while C. mas fruits showed elevated levels of shikimic acid. Strong positive correlations were found between TPC, TFC, and ABTS activity (r > 0.90), indicating that flavonoids are key contributors to antioxidant capacity. Principal component analysis clearly discriminated samples according to species, with minor effects of sampling location. Overall, C. mas fruits demonstrated a superior antioxidant potential associated with a rich and diverse phenolic profile. In contrast, J. communis fruits were distinguished by a higher content of organic acids and a species-specific phenolic pattern. These findings highlight the nutritional and functional value of both species, supporting their potential application in functional foods and nutraceuticals.