Comparative antioxidant and antibacterial activities of ethanol extract from different parts of Syzygium gratum

Herbal extracts are widely recognized as valuable sources of bioactive compounds with antioxidant and antimicrobial properties. However, variations in biological activity among different plant parts remain insufficiently explored for many medicinal plants. This study aimed to comparatively evaluate the antioxidant and antimicrobial activities of extracts obtained from four different parts including young leaves (YL), mature leaves (ML), branches (BR), and twigs (TW) of Syzygium gratum. Plant materials were extracted using ethanol with maceration method, and antioxidant activity was determined through total phenolic content (TPC) analysis along with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, while antibacterial activity was evaluated against two selected microorganisms, E. coli, S. aureus using disc diffusion method. Among the tested extracts, the extract from young leaves exhibited the strongest antioxidant capacity with 18.01±2.25 mg gallic acid equivalents per gram of dried weight for TPC and 67.05% for DPPH assay. In addition, the extract showed the most antimicrobial effects with 10.8±0.1 and 11.1±0.1 mm for E. coli and S. aureus, respectively. The YL extract was further investigated the chemical constituents by using GC–MS technique, and the result revealed that the four major constituents were Dihydrooroxylin A, neophytadiene, tetrapentacontane, and g-tocopherol. The observed data was likely associated with major GC–MS identification constituents, including Dihydrooroxylin A and γ–tocopherol, which have been previously reported to exhibit antioxidant and antimicrobial effects. In addition, these data highlighted the importance of plant–part selection especially for YL extract in maximizing biological activity and supported the potential application of S. gratum as a natural source of antioxidant and antimicrobial agents. GRAPHICAL ABSTRACT HIGHLIGHTS Ethanol extracts obtained from different parts of Syzygium gratum exhibited moderate antioxidant and antibacterial activities. Extracts from young leaves showed higher biological activities comparing with other parts, in agreement with their phenolic content and the presence of bioactive constituents detected by GC–MS analysis. These results indicate the relevance of plant-part selection for the rational and sustainable utilization of Syzygium gratum in environmentally related chemical applications.