4种浮萍提取物的抗菌活性和黄酮含量

Antimicrobial activities and flavonoid contents of the extracts from four strains of duckweed

浮萍(Lemnaceae)生长在微生物丰富的污水表面,为了研究浮萍抗菌机制,为浮萍抗菌物质活性筛选以及动植物病原菌和人类致病微生物感染机制研究提供依据,用不同极性的溶剂对浮萍进行提取,牛津杯法(Oxford Cup)及最小抑菌浓度(MIC)测定比较绿萍zh0018、少根紫萍zh0224以及多根紫萍zh0003、zh0225四种浮萍提取物的体外抗菌活性,并用分光光度法结合高效液相色谱(HPLC)测定分析提取物总黄酮含量以及成分差异.结果表明:浮萍甲醇提取物、95%乙醇提取物对枯草芽孢杆菌、金黄色葡萄球菌、铜绿假单胞菌、大肠杆菌、农杆菌均有不同程度的抗菌活性,其中多根紫萍zh0225甲醇提取物抗菌活性最强(MIC:6.25 mg/mL),其次为绿萍;各萃取物中乙酸乙酯相活性最强(MIC:0.78 mg/mL),其次为正丁醇相.分光光度法测得绿萍甲醇提取物总黄酮含量较高,为提取物的9.8%,其次为少根紫萍甲醇提取物,为8.1%,其中多根紫萍zh0225乙酸乙酯相含量最高,为萃取物的22.46%,其次为正丁醇相,为17.2%.HPLC测得不同浮萍提取物黄酮成分差异较大,两株多根紫萍成分相似而含量不同.研究表明,结合浮萍自身的特性和提取物抗菌活性的大小及黄酮含量,筛选多根紫萍zh0225乙酸乙酯萃取相作为优良浮萍品种提取活性物质以及开展药物生产具有巨大潜力.

Duckweed （Lemnaceae） is a plant which grows in the sewage surface teeming with rich microbes, and it is proved that duckweed has a protective mechanism against microbes. In order to study the antibacterial mechanism of duckweeds and provide the basis for screening anti-bacterial substances and studying the infection mechanism of plant and animal pathogens or human pathogenic microorganisms, we first extracted using solvents with different polarities four strains of duckweed belonging to Lemna minor L. zh0018, Landoltia punctata zh0224, Spirodela polyrrhiza （L.） Schleid zh0003 and zh0225. The antimicrobial activities of their extracts were compared by Oxford Cup method and the minimum inhibitory concentration （MIC） measurement. Meanwhile, the contents and the composition of total flavonoids were determined by spectrophotometry combined with high performance liquid chromatography （HPLC） analysis. The results showed that the methanol extracts and 95% ethanol extracts of the duckweed had different degrees of antimicrobial activities against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Agrobacterium. The antimicrobial activity of the methanol extracts from S. polyrrhiza was the strongest （MIC： 6.25 mg/mL）, followed by L. minor L. extracts; the ethyl acetate phase had the strongest activity （MIC： 0.78 mg/mL） followed by the n-butanol phase. The methanol extracts of L. minor L. had the highest level of total flavonoids content, 9.8% of the total extracts, followed by the 8.1% content of the methanol extracts of L. punctata. In addition, the ethyl acetate phase of S. polyrrhiza zh0225 methanol extracts had the highest content of total flavonoids （22.46%） followed by the 17.2% content of the n-butanol extracts. In HPLC measurement, the composition of flavonoids showed tremendous difference among the duckweed extracts, with the two strains of S. polyrrhiza having similar composition with different contents. The results suggested an enormous potential of S. polyrrhiza zh0225 as an excellent duckweed species for active substance extraction and pharmaceutical production.