| Summary: | 碩士 === 國立屏東科技大學 === 農園生產系 === 93 === St. John’s wort has active ingredients for anti-depression, anti-virus, anti-bacteria and anti-oxidation, which is widely used as conventional herb in foreign countries. The warm weather and high moisture climate in Taiwan is suitable environment for the St. John’s wort cultivation. The purpose of this experiment was to study the variations of St. John’s wort antioxidant capacity and the antimicrobial activity for the leaves and stems of plant. It will be comprised of three steps separately so as to analyze the variations of St. John’s wort in antioxidant level and antioxidant capacity: (a) The variations in phenolics compound content and anti-oxidation by the harvest time, the parts of plant, and the drying treatments. (b) The phenolics content and anti-oxidation by extracting process and drying treatments. (c) The anti-bacteria activity of the Gram-bacteria by the drying treatments and the analysis of its pH level.
The contents of MDA, hydrogen peroxide, glutathione, SOD, total phenolics, total flavonoids and hypericin in leaves showed higher than stems when the St. John’s wort were harvested in different month and dehydrated in different process; the leaves revealed better performance than the stems in anti-oxidation.
The total phenolics contents in leaves and stems and glutathione contents in leaves were accumulated in higher concentrations if delayed in their harvest time, the herbs were harvested in August showed highest content values. The SOD in leaves and stems, total flavonoids in leaves, hypericin and glutathione in the stems harvested in June had highest concentration. The leaves processed by freeze drying method showed higher total phenolics, glutathione and SOD content. The total flavonoids and hypericin contents for the leaves drying in 80℃ were low. The leaf harvested in August showed significant higher antioxidant activity and superoxide anion scavenging activity. However, in June DPPH radical scavenging activity was significantly higher.
The content of total phenolics, total flavonoids and hypericin for St. John’s wort extracted in water decreased by increasing the extract time. The same result in the the antioxidant activity, DPPH radical scavenging activity and superoxide anion scavenging activity was found.
The total phenolics content in leaves was highest when extracting by methanol other than different solvents. Extracting by water obtained lowest total flavonoids content as compared to the other three kinds of solvent. The highest content obtained in any solvent was through freeze drying process. Extracting by acetone and freeze drying got highest hypericin content. The antioxidant activity decreased when increasing the incubation time, extracting in methanol performs better. Extracting by methanol and ethanol showed the highest DPPH radical scavenging activity. The superoxide anion scavenging activity increased by increasing the concentration of extracts, extracting in methanol performs better. The total phenolics content extracting in water and acetone showed positive correlation with DPPH radical scavenging activity.
The results showed obvious antimicrobial activity for six kinds of gram-positive and negative bacteria in different concentrations of ethanol extracts. The antimicrobial activity increased by the concentration of extracts. The antimicrobial activity was found in the leaves and the stems. The antimicrobial activity of extracts showed best result in acid environment, but were generally fair among pH 4-8.
Overall, parts of plant, harvest time, drying treatment, extracting time and solvent could affected on the total phenolics contents, total flavonoids content, hypericin and anti-oxidation of St. John’s wort. All the extracts from St. John’s wort showed antimicrobial activity for gram bacteria.
|
|---|
