Studies On The Processing Of Water Dropwort Tea And Its Bioactivity

Water dropwort has a long cultivation history and wide distribution in China. However, the cooking method is as simple as fried vegetables. Reports on water dropwort were mainly focused on separation and identification of flavonoids and phenolic acids, and the extraction of them was optimized. There are few reports about the effects of processing on its bioactivities, such as antioxidant and liver protecting. On these bases, some technologies of tea processing were applied to make the material into some teas, which are more convenient to eat, longer to store, and more economic value to be added. Firstly, the main nutrients of leaves and stems were detected separately. Then the water dropwort was made into green tea, black tea and dark tea according to the characteristic of its nutrients composition. The control sample was the dried water dropwort. Secondly, the total flavonoids of four samples were determined and the proper extract condition was selected. Thirdly, the abilities of antioxidant and antitumor bioactivities were evaluated. Lastly, the aroma components were detected by SPME/GC-MS and sensory evaluations were made of four samples. All the results were considered to choose a proper process method of water dropwort tea.(1) Consider that the content of many compounds are varied to different parts, the leaf and stem were determined separately. The result showed that the contents of water, protein, total phenols, and total flavonoids in the leaves were higher than in stems. But the contents of ash, fat, crude fiber, total sugar were the opposite. According to the processing of common teas and some other potherb teas, the water dropwort was made into green tea, black tea and dark tea.(2) The categories and contents of the flavonoids in four samples were determined by HPLC, which agrees the results of total flavonoids’ determination using the method of pectrophotometry. The contents of flavonoids in green tea and in control sample were approximate, reached42.96and39.35mg/g separately. But the contents in black tea and dark tea reached only30.01and19.5mg/g. The common compound in four samples was rutin, but the contents varied a lot, from27.3mg/g to1.28mg/g. The kaempferol was only detected in dark tea. The quercetin was detected in black tea and dark tea, but no quercetin in control sample and green tea. The probable explanation was that the process of fermentation made the quercetin uncombined that could be detected which was combined with glucoside at first. In choosing the extract condition, the temperature of water and the concentration of alcohol were considered. The results showed that temperature of70℃and70%alcohol concentration were the best.(3) During the scavenging activity of DPPH·free radical, ABTS+radical, oxygen radical absorbing and the reduction of iron ion experiments, the green tea had the strongest antioxidant ability, which was nearly the twice times of the other samples in numbers. As the different evaluation mechanisms of different assays, the results of the other three samples varied. A phenomena was observed that the capability of antioxidant of dark tea was lower than that of the control sample, which showed that the processing method of dark tea reduced the antioxidant ability rather improve. After analyzing the process, the reason may be the unique link of the process which is called pile fermentation. Besides the four samples mentioned above, two new samples were added in the experiment of antitumor, which were freeze-drying powder of ethanol and product of purification through macroporous resin. However, none of all the six samples showed inhibition of the cancer cells of PC-3and HepG2.(4) In order to analyze the effect of different processing methods on the volatile compounds of water dropwort, four different samples were analyzed by SPME/GC-MS. Total of47components were identified, including16terpenes,8olefins,4ketones,4alcohols,6alkanes and so on. As to each sample,25components in control group,21components in dark tea,33components in black tea and23components in green tea were identified. However, only10components were identified in all of four samples. The main volatile compounds were terpenes and β-farnesene, a-bergsmotene, a-pinene were the largest amount components. All these results would offer guide to choose proper processing methods and for the development of water dropwort teas. The green tea got the highest mark in the sensory evaluation.