Abstract: In this study,we investigated the effects of Ca²⁺ and Mg²⁺ on the extraction and antibacterial activity of total flavonoids from sweet potato leaves.Single-factor experiments were conducted to determine the optimal levels of Ca²⁺ and Mg²⁺ concentration,solid-liquid ratio,and ethanol concentration and extraction time.Response surface method was used to optimize extraction condition by introducing Ca²⁺ and Mg²⁺ in sweet potato leaf flavonoids extracts.The optimum extraction process was Ca²⁺ concentration:187 mg/L,Mg²⁺ concentration:176 mg/L,ethanol concentration:71%,the material liquid:1:40 and extraction time:1 h.The extraction yield was 2.76%,which is slightly higher than that of the traditional extraction technology.The MIC values of Escherichia coli, Staphylococcus aureus and Bacillus subtilis were 69.69,69.69 and 34.85 μg/mL,which was significantly lower than those of sweet potato leaves flavonoids extracts without Ca²⁺ and Mg²⁺ (250,125 and 62.5 μg/mL).Therefore,the extracts contained Ca²⁺ and Mg²⁺ could significantly enhance the antibacterial activity.

Key words: Ca²⁺ and Mg²⁺ , sweet potato leaves, flavonoids, response face method, antibacterial activity