Abstract:This paper aimed to study the total phenols and flavonoids in different polar solvents of the 95%ethanol extract of Plumeria rubra L.，and evaluate their antibacterial，antioxidant and antitumor activities in vi?tro.Petroleum ether，chloroform，ethyl acetate and water were used to extract four active substances from the ethanol extracts of P.rubra and the contents of total phenols and total flavonoids in each fraction were deter?mined.The minimum inhibitory concentration（MIC）of each fraction against Escherichia coli，Staphylococcus aureus，Acinetobacter baumannii，Klebsiella pneumoniae and Pseudomonas aeruginosa was determined by the broth dilution method，and the scavenging capacity against DPPH·，ABTS+·and·OH was measured.In addi?tion，the anti?proliferation effect of each fraction on human hepatocellular carcinoma cells（SMMC?7721，HepG2），human breast cancer cells（MDA?MB?231，MCF?7），human colon cancer cells（HCT?116），hu?man colorectal adenocarcinoma epithelial cells（DLD?1），human malignant melanoma cells（A375）and hu?man glioma cells（U251）was evaluated by Cell Counting Kit?8 assay.The results showed that the highest con?tents of total phenols and total flavonoids were obtained from ethyl acetate fraction，which were（57.73±0.09）mg GAE/g and（558.88±0.99）mg RE/g，respectively.All P.rubra extracts had antioxidant，antibacterial and antitumor abilities and was dose?dependent with the concentration.Among them，the ethyl acetate fraction had the strongest antibacterial and antioxidant abilities，with the MIC against the five bacteria ranging from 0.5 mg/mL to 1.0 mg/mL and the IC50 of scavenging DPPH·，ABTS+· and ·OH being 14.94，15.43 and 74.61 μg/mL，respectively.The chloroform fraction inhibited the proliferation of the above eight tumor cells most，with the IC50 ranging from 9.12 μg/mL to 40.14 μg/mL.In conclusion，each fraction of P.rubra has strong antibacterial，antioxidant and antitumor activities，which provides a certain theoretical basis for the de?velopment and utilization of P.rubra as food health care products or drugs.