In Vitro Evaluation of Antioxidant and Anti-Inflammatory Activities of Ethanolic Leaf Extract of Syzygium polyanthum

Bay leaf (Syzygium polyanthum (Wight) Walp.) has traditionally been used for conditions associated with oxidative stress and inflammation. To date, few studies have evaluated antioxidant and anti-inflammatory activities jointly in vitro. This study examined the antioxidant and anti-inflammatory activities of the ethanolic leaf extract of Syzygium polyanthum, prepared by maceration with 96% ethanol. Antioxidant activity was assessed using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), nitric oxide (NO) radical-scavenging, and ferric reducing antioxidant power (FRAP) assays. Anti-inflammatory activity was evaluated using red blood cell membrane stabilization against heat- and hypotonic-induced hemolysis and inhibition of protein denaturation. Total phenolic content (TPC) and total flavonoid content (TFC) were also determined. The extract contained 89.443 ± 1.201 mg GAE/g of total phenolics and 171.637 ± 1.016 mg QE/g of total flavonoids. It exhibited strong to very strong radical-scavenging activity, with IC₅₀ values of 57.446 ± 0.394 µg/mL for DPPH, 36.750 ± 0.354 µg/mL for ABTS, and 58.853 ± 0.233 µg/mL for NO. FRAP reducing capacity increased with concentration, reaching 35.826 ± 1.182 mg QE/g at 100 µg/mL. At 100 µg/mL, the extract inhibited heat-induced hemolysis by 75.133%, hypotonic-induced hemolysis by 68.310%, and protein denaturation by 65.839%. The extract exhibited radical-scavenging activity, reducing capacity, and anti-inflammatory effects in vitro, supporting its potential as a natural source of bioactive compounds. Further studies are needed to assess its safety and effects in vivo.