Investigation of the in vitro antioxidant, anti-inflammatory, antibacterial, and α-amylase and α-glucosidase inhibitory activities of Nauclea orientalis flower extracts: Biological evaluation of Nauclea orientalis flowers

Nauclea orientalis is a medicinal plant widely distributed in Southeast Asia; however, the biological activities of its flowers remain poorly explored. Therefore, this study aimed to evaluate the in vitro antioxidant, anti-inflammatory, antibacterial, and carbohydrate-hydrolyzing enzyme inhibitory activities of N. orientalis flower extracts and fractions. The crude ethanol extract was sequentially partitioned into n-hexane, dichloromethane, and ethyl acetate fractions. Total polyphenol content (TPC) and total flavonoid content (TFC) were determined using the Folin–Ciocalteu and aluminum chloride colorimetric methods, respectively. Biological activities were assessed through multiple in vitro assays. Among all tested samples, the ethyl acetate fraction exhibited the highest TPC and TFC, reaching 148.80 ± 1.57 mg GAE/g extract and 127.15 ± 0.90 mg QE/g extract, respectively. This fraction also demonstrated the strongest antioxidant activity across ABTS•+, DPPH, FRAP, TAC, and RP assays. In anti-inflammatory evaluations, the ethyl acetate fraction showed remarkable inhibitory effects in red blood cell membrane stabilization, bovine serum albumin denaturation, and nitric oxide scavenging assays. Furthermore, this fraction exhibited potent inhibitory activity against α-amylase and α-glucosidase, with IC50 values of 68.54 ± 1.42 and 41.04 ± 1.00 µg/mL, respectively. Antibacterial assays revealed broad-spectrum activity against both Gram-positive and Gram-negative bacteria, particularly against Listeria innocua and Staphylococcus aureus. The ethyl acetate fraction also displayed the lowest MIC and MBC values among all tested extracts. Overall, N. orientalis flowers represent a promising natural source of bioactive compounds with multifunctional pharmacological potential for future pharmaceutical and nutraceutical applications.