Hormetic Antioxidant Effects of Uncaria gambir on Male Reproductive Function: A Comprehensive Experimental and Computational Analysis

Oxidative stress is a key mechanism underlying nicotine-induced male reproductive dysfunction, yet evidence-based phytopharmacological interventions remain limited. Uncaria gambir Roxb., a catechin-rich medicinal plant from West Sumatra, Indonesia, exhibits strong antioxidant potential; however, a comprehensive multi-regional evaluation combined with in vivo androgenic assessment is lacking. This study aimed to characterize the antioxidant activity, phytochemical composition (HPLC-DAD), and antimicrobial properties of gambir extracts from three production regions (Halaban, Mungka, and Pesisir Selatan), to evaluate catechin pharmacokinetics in silico (PASS Online; SwissADME), and to assess dose-dependent effects in male Wistar rats exposed to nicotine (n = 36). The Halaban extract showed the highest antioxidant activity (IC50 = 6.99 ± 0.28 µg mL−1) and catechin content (7.91 ± 0.07 mg g−1). All extracts demonstrated broad-spectrum antimicrobial activity. PASS analysis predicted strong membrane integrity agonism (Pa = 0.950) and HMOX1 induction (Pa = 0.778), while SwissADME indicated favorable pharmacokinetic properties, including full Lipinski compliance and high gastrointestinal absorption. In the in vivo study, gambir Halaban extract at 300 mg kg−1 day−1 significantly increased follicle-stimulating hormone, luteinizing hormone, and testosterone levels compared to controls (p < 0.05), exceeding baseline values and indicating HPG axis stimulation. A non-linear (hormetic) response was observed, with reduced efficacy at higher doses. These findings highlight bioactive-rich gambir as a promising multi-target natural antioxidant for mitigating oxidative-stress-related reproductive dysfunction, warranting further mechanistic and translational studies.