Abstract
<title>Abstract</title> <p> Background Breast cancer remains the most frequently diagnosed malignancy and a leading cause of cancer mortality in women worldwide, with an estimated 2.3 million new cases recorded globally in 2022 (Bray et al., 2024). Aromatase (CYP19A1), the rate-limiting enzyme in estrogen biosynthesis, is a clinically validated molecular target for endocrine therapy in estrogen receptor-positive breast cancer. Plant-derived phytochemicals with antioxidant and aromatase-modulating potential represent a promising, low-toxicity avenue for adjunct chemoprevention. <italic>Psidium guajava</italic> L. (guava) is a widely distributed medicinal plant with an extensively documented phytochemical and pharmacological profile. Objective This study aimed to (i) qualitatively screen the phytochemical composition of <italic>P. guajava</italic> leaf extract, (ii) evaluate its in vitro antioxidant potential using three complementary assays, (iii) characterize its volatile and semi-volatile chemical constituents by gas chromatography–mass spectrometry (GC–MS), and (iv) computationally evaluate the binding potential of the identified phytoconstituents against human aromatase (CYP19A1) using in silico molecular docking, in the context of breast cancer chemoprevention. Methods Powdered guava leaves were extracted and subjected to standard qualitative phytochemical tests. Antioxidant activity was assessed using DPPH, ABTS and hydrogen peroxide (H <sub>2</sub> O <sub>2</sub> ) radical scavenging assays, with ascorbic acid as reference standard. GC–MS analysis was performed and peaks were identified against the NIST spectral library. Seven representative phytoconstituents (isophytol, palmitic acid, stearic acid, squalene, α-tocopherol, stigmasterol and lupeol, plus lupenone and norcassamine) were retrieved from PubChem and docked against the human aromatase crystal structure (PDB: 3EQM) using the CB-Dock2 blind-docking server (AutoDock Vina scoring engine). Results Phytochemical screening indicated the presence of [flavonoids, phenolics, terpenoids, steroids, tannins, saponins; insert your findings]. The extract exhibited dose-dependent radical scavenging in all three antioxidant assays, with IC <sub>50</sub> values of 52.4 ± 2.1 µg/mL (DPPH), 78.5 ± 3.2 µg/mL (ABTS), 96.2 ± 4.1µg/mL (H <sub>2</sub> O <sub>2</sub> scavenging), compared with ascorbic acid. GC–MS analysis revealed seventeen major constituents (retention time 13.84–66.79 min), dominated by phytol-type diterpenes, fatty acid methyl esters, and triterpenoid/sterol compounds including squalene, stigmasterol, lupeol and α-tocopherol. Molecular docking against aromatase identified lupeol (− 9.1 kcal/mol) and lupenone (− 9.0 kcal/mol) as the strongest binders, followed by norcassamine (− 8.0 kcal/mol), α-tocopherol and stigmasterol (− 7.7 kcal/mol each), isophytol (− 7.6 kcal/mol) and squalene (− 7.4 kcal/mol), while the saturated fatty acids palmitic and stearic acid showed comparatively weak affinity. Conclusion <italic>P. guajava</italic> leaf extract is a chemically rich source of antioxidant and pharmacologically active phytoconstituents. The strong in silico binding of lupeol and lupenone within the aromatase active site, supported by hydrogen bonding and extensive hydrophobic contacts with key catalytic residues, nominates these triterpenoids as promising natural aromatase-inhibitor leads warranting in vitro enzymatic validation and molecular dynamics simulation for breast cancer chemoprevention. </p>