Three muscadine grape genotypes (Muscadinia rotundifolia (Michx.) Small) were evaluated for their metabolite profiling and antioxidant activities at different berry developmental stages. A total of 329 metabolites were identified using UPLC-TOF-MS analysis (Ultimate 3000LC combined with Q Exactive MS and screened with ESI-MS) in muscadine genotypes throughout different developmental stages. Untargeted metabolomics study revealed the dominant chemical groups as amino acids, organic acids, sugars, and phenolics. Principal component analysis indicated that developmental stages rather than genotypes could explain the variations among the metabolic profiles of muscadine berries. For instance, catechin, epicatechin-3-gallate, and gallic acid were more accumulated in ripening seeds (RIP-S). However, tartaric acid and malonic acid were more abundant during the fruit-set (FS) stage, and malic acid was more abundant in the veraison (V) stage. The variable importance in the projection (VIP > 0.5) in partial least-squares–discriminant analysis described 27 biomarker compounds, representing the muscadine berry metabolome profiles. A heatmap of Pearson’s correlation analysis between the 27 biomarker compounds and antioxidant activities was able to identify nine antioxidant determinants; among them, gallic acid, 4-acetamidobutanoic acid, trehalose, catechine, and epicatechin-3-gallate displayed the highest correlations with different types of antioxidant activities. For instance, DPPH and FRAP conferred a similar antioxidant activity pattern and were highly correlated with gallic acid and 4-acetamidobutanoic acid. This comprehensive study of the metabolomics and antioxidant activities of muscadine berries at different developmental stages is of great reference value for the plant, food, pharmaceutical, and nutraceutical sectors.

Muscadine grape is rich in stilbenes, which include resveratrol, piceid, viniferin, pterostilbene, etc. Resveratrol has been extensively studied for its biological activities; however, the synergistic effect of stilbene compounds in berry extracts is poorly understood. The aim of this study was to evaluate the anti-cancer activity of stilbene-rich muscadine berry extract and pure resveratrol. Stilbenes were extracted from ripened berries of muscadine grape cultivars, Pineapple, and Southern Home. HPLC analysis was performed to determine quantity of stilbenes. The extracts were tested for their cytotoxic activity against A549 (lung carcinoma cells), triple negative breast cancer (HCC-1806) and HepG2 (human liver cancer) cells. The stilbene-rich extracts of the muscadine berry extracts showed cytotoxic activity against all of the cells tested. The extracts at 1 μg/mL induced death in 50–80% of cells by 72 h of treatment. About 50 μg/mL of resveratrol was required to induce a similar response in the cells. Further, modulation of genes involved in tumor progression and suppression was significantly (p < 0.0005) higher with the HepG2 cells treated with stilbene-rich berry extracts than the pure resveratrol. This shows that the synergistic activity of stilbenes present in muscadine grape berries have more potent anti-cancer activity than the resveratrol alone.

Wines contain a large array of phenolic compounds, belonging to non-flavonoids, flavonoids and phenolic-protein-polysaccharide complexes. Phenolics in wine are responsible for wine color, astringency, and bitterness. This study evaluates phenolic composition of commercial and experimental wines derived from bunch (Vitis vinifera) and muscadine (Vitis rotundifolia) grapes to determine compositional differences in phenolics. HPLC analysis of wines showed that majority of phenolic compounds eluted during the first 30 min. Of the red wines tested, Château Cabrieres Chateauneuf de Pape (Rhone) showed the simplest phenolics profile while Cabernet Sauvignon (Vitis vinifera-California) showed the most complex profile. The phenolics composition of red and white wines varied greatly. Some white wines from bunch grape were devoid of any phenolics. Among muscadine white wines, some contained large number of phenolic compounds while the others showed smaller number of phenolic compounds. These data suggested that both the red and white wines contained a complex mixture of phenolic compounds whose content and composition varied by brand suggesting that the wine processing technique greatly influences phenolics composition of wines than color of the wine. Muscadine red wines were quite distinct than that of the bunch grapes, indicating that grape chemistry has a greater influence on wine phenolic composition. Key words: Grape, HPLC, phenolics, red and white wines.

Muscadine grapes are renowned for their unique traits, natural disease resistance, and rich bioactive compounds. Despite extensive research on their phytochemical properties, microbial communities, particularly endophytic bacteria, remain largely unexplored. These bacteria play crucial roles in plant health, stress tolerance, and ecological interactions. This study represents the first comprehensive effort to isolate, identify, and functionally characterize the bacterial endophytes inhabiting muscadine grape berries using a culture-dependent approach. We isolated diverse bacterial species spanning six genera—Bacillus, Staphylococcus, Paenibacillus, Calidifontibacillus, Curtobacterium, and Tatumella. Microscopic and physiological analysis revealed variations in bacterial morphology, with isolates demonstrating adaptability to varied temperatures. Cluster-based analysis indicated functional specialization among the isolates, with species from Pseudomonadota and Actinomycetota exhibiting superior plant growth-promoting abilities, whereas Bacillota species displayed potential biocontrol and probiotic properties. Among them, Tatumella ptyseos demonstrated exceptional plant growth-promoting traits, including indole-3-acetic acid production, nitrogen fixation, phosphate solubilization, and carbohydrate fermentation. Additionally, Bacillus spp. showed presumptive biocontrol potential, while Paenibacillus cineris emerged as a potential probiotic candidate. The identification of Calidifontibacillus erzurumensis as a novel endophytic species further expands the known biodiversity of grape-associated microbes. These findings provide insights into the metabolic diversity and functional roles of muscadine grape-associated endophytes, highlighting their potential for agricultural and biotechnological applications.

Stilbenoids such as t-piceid, t-resveratrol, ε-viniferins, and t-pterostilbene can differ significantly among grape cultivars and years due to variation in environmental conditions and subsequent stressors encountered during a year. This study evaluated diverse muscadine grape cultivars for their ability to consistently produce four major stilbenoids such as t-piceid, t-resveratrol, ε-viniferins, and t-pterostilbene irrespective of environmental changes that can impact their production. Berries from forty-two muscadine grape cultivars were collected for three years (2013, 2014, and 2015) to measure stilbenoids. Results showed significant differences in the composition of four stilbenoids among the muscadine cultivars. The highest level of stilbenoids was observed in ‘Fry Seedless’ (270.20 µg/g fresh weight) in each of the three consecutive years tested followed by ‘Pride’ (46.18 µg/g fresh weight) while ‘Doreen’ produced the lowest level of stilbenoids (1.73 µg/g fresh weight). Results demonstrated that certain muscadine grape cultivars consistently produced varied levels of the four major stilbenoids year after year. Based on the total content of stilbenoids, the 42 muscadine cultivars studied were grouped into three categories such as High, Medium and Low stilbenoid-containing cultivars. This information will help establish new vineyards with cultivars that are less prone to variations in environmental conditions and can consistently produce stilbenoid-rich muscadine grape berries with enhanced market value to promote consumer health.