Analysis of Chemical Constituents in Violae Herba and Investigation of Its Antioxidant Activity in Vitro / 中国实验方剂学杂志

ABSTRACT

Objective:To investigate the chemical constituents and antioxidant activities of Violae Herba from the Violaceae. Method:The 5 kg of Violae Herba was refluxing extracted with 3 times the amount of 95% ethanol for three times， then the extracting solution was combined， filtrated， concentrated under vacuum to get the total extract. Seven corresponding fractions were eluted with petroleum ether， dichloromethane， dichloromethane-methanol （50∶1， 10∶1， 5∶1， 2∶1） and methanol by silica gel column chromatography （60-100 mesh） on the total extract. Each fraction was isolated and purified by normal phase silica gel column chromatography， octadecylsilane chemically bonded silica （ODS） column chromatography， Sephadex LH-20 column chromatography and preparative high performance liquid chromatography （HPLC）， respectively. The structures of the obtained compounds were identified by spectroscopic methods of nuclear magnetic resonance （NMR）， mass spectroscopy （MS） and infrared spectroscopy （IR）. Meanwhile， some of these compounds isolated from Violae Herba were carried on the 1，1-diphenyl-2-picrylhydrazyl （DPPH） free radical scavenging experiment. Result:Fourteen compounds were isolated from the 95% ethanol extract of Violae Herba， including <italic>N</italic>-acetyl-1-ethyl ester glutamic acid （<bold>1</bold>）， <italic>N</italic>-acetyl glutamic acid-1-ethyl-5-methyl ester （<bold>2</bold>）， aurantiamide （<bold>3</bold>）， <italic>rel</italic>-（2<italic>α</italic>，3<italic>β</italic>）-7-<italic>O</italic>-methylcedrusin （<bold>4</bold>）， oleanolic acid （<bold>5</bold>）， <italic>α</italic>-tocopherol-quinone （<bold>6</bold>）， tectochrysin （<bold>7</bold>）， isoscopoletin （<bold>8</bold>）， esculetin （<bold>9</bold>）， 24-ethylcholesta-4，24（28）<italic>Z</italic>-dien-3-one （<bold>10</bold>）， stigmasta-4，25-dien-3-one （<bold>11</bold>）， <italic>β</italic>-sitostenone （<bold>12</bold>）， <italic>β</italic>-sitosterol （<bold>13</bold>）， （24<italic>R</italic>）-3<italic>β</italic>-hydroxy-ethylcholest-5-en-7-one （<bold>14</bold>）. Conclusion:Compound <bold>2</bold> is a new natural product， compounds <bold>1</bold>， <bold>4</bold>， <bold>6</bold>， <bold>7</bold>， <bold>10</bold>-<bold>12 </bold>are isolated from the genus <italic>Viola</italic> for the first time. Compound <bold>9</bold> has significant antioxidant activity， while compounds <bold>2</bold>， <bold>6 </bold>and<bold> 8</bold> have certain DPPH free radical scavenging activity.