Punica Granatum Flower and Hibiscus Sabdariffa Calyx: A Narrative Review of Phytochemistry, Antioxidant Mechanisms, and Therapeutic Potential

Background: Oxidative stress, resulting from an imbalance between free radical production and antioxidant defense mechanisms, underlies the pathogenesis of numerous chronic diseases including cardiovascular disorders, cancer, diabetes, and neurodegenerative conditions. The global burden of these diseases continues to rise, driving demand for safe, effective natural antioxidants. Objective: This narrative review aims to synthesize and critically evaluate the available literature from 2010 to 2025 on the phytochemical composition, antioxidant mechanisms, and therapeutic potential of Punica granatum (pomegranate) flower and Hibiscus sabdariffa (roselle) calyx. Methods: A literature search was conducted in PubMed, Scopus, Web of Science, Google Scholar, and regional databases using keywords including "Punica granatum flower," "pomegranate flower," "Hibiscus sabdariffa," "roselle," "antioxidant," "oxidative stress," "Nrf2," "polyphenols," "ellagitannins," and "anthocyanins." Studies published between 2010 and 2025 reporting phytochemical characterization, in vitro antioxidant assays, in vivo antioxidant effects, and relevant pharmacological activities were included. Key data were extracted and synthesized thematically. Outcomes: Pomegranate flowers are rich in ellagitannins, particularly punicalagin, with DPPH radical scavenging activity reaching IC50 values as low as 1.715 μg/mL in ethyl acetate fractions—among the highest reported for natural antioxidants. Hibiscus sabdariffa calyces contain high concentrations of anthocyanins, primarily delphinidin-3-O-sambubioside and cyanidin-3-O-sambubioside, with purified anthocyanin extracts demonstrating DPPH IC50 values of 6.8 μg/mL and ABTS IC50 of 5.2 μg/mL. Both extracts activate the Nrf2 signaling pathway, upregulate endogenous antioxidant enzymes including superoxide dismutase, catalase, and glutathione peroxidase, and demonstrate hepatoprotective, cardioprotective, and neuroprotective effects in preclinical models. Their complementary phytochemical profiles—ellagitannins providing sustained antioxidant effects through urolithin formation and anthocyanins providing immediate radical scavenging—provide a strong scientific rationale for polyherbal combinations. Wider Implications: This evidence base supports the potential of these medicinal plants for developing evidence-based antioxidant interventions. Further research should focus on clinical validation of combined extracts and optimization of extraction methods to maximize synergistic interactions.