End of Year Report

This year I had the opportunity to take part in a research project under the guidance of Dr. Elmer Mojica. My study was to determine the phenol content and antioxidant properties of different tea samples. Going into my first research project I was nervous because I had never worked alongside a professor before and I was not sure how I would manage doing research on my own. Before starting to do actual work, I sat with Dr. Mojica and we discussed and researched different protocols for the two assays we wanted to do our research on. Doing the beforehand research was interesting because I was able to become familiar with the software needed to perform scientific searches. I was able to find different scientific articles that performed the same assays that Dr. Mojica and I wanted to use and see the protocol that those scientists used. As a team, Dr. Mojica and I were able to create two separate protocols for the DPPH and Folin – Ciocalteu assays. I also learned how to operate the computational software IGOR. I used this software to put the results of my research into. Once the results were entered, the software then created graphs of all the results which made it easier to draw conclusions from them. Starting to work in the laboratory was a new experience for me. I have worked in the laboratory during previous semesters in regards to my classes but I have always worked with a group of two to three people. This research project was the first time I was performing experiments with instruments by myself. I was nervous because I didn’t want to break the instruments I was working with. The main instrument that I worked with this year was the Ultraviolet – Visible (UV – Vis) spectrometer instrument. Dr. Mojica was in the lab with me while I was doing research to make sure I was doing everything properly. At the conclusion of my research project, I learned valuable skills that were needed to operate the UV – Vis spectrometer, an instrument that I will use in my future career, as well as how to operate the software IGOR. From this research study, I will be able to bring my research to the national conference in New Orleans, Louisiana and present it to other professionals in my field. Being given the funds to pursue this research project with Dr. Mojica has strengthened my ability to share my ideas in a professional environment. The skills that I learned this year will benefit me greatly in both my academic and post – gradation aspirations.

Tea is the most consumed beverage in the world next to water. The total amount of tea produced and consumed in the world can be broken into 78% black, 20% green and less than 2% is oolong tea. Black tea is consumed primarily in Western countries and in some Asian countries, whereas green tea is consumed primarily in China, Japan, India, and a few countries in North Africa and the Middle East. Oolong tea production and consumption are confined to southeastern China and Taiwan. Tea is of great importance to the economy and medicine. It exists in wide varieties and has gained much attention due to its health – promoting benefits. Among these benefits are anti-apoptotic anticancer, antimutagenic, neuroprotective, antihyperglycemic, antimicrobial, and inflammatory effects. All of these activities are related to the antioxidant activity of chemical compounds present in teas, especially flavonoids and phenolic acids. The evaluation of total and individual quantification of phenolic compounds is essential to correlate with the biological activity. Knowing the antioxidant property of teas is important to determine their health benefits. In this study, the phenol content and antioxidant properties of the water extracts of 12 commercially available teas from one company (Bentley’sÔ) were evaluated and compared with one another. The total phenolic content was determined by the Folin-Ciocalteu method with gallic acid used as the standard. The antioxidant properties were evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay system. The methodology to this study are the following. Bags from the tea samples were dipped into 50 mL of freshly boiled water for five minutes. The tea infusions produced were collected and analyzed for phenol content and antioxidant properties using ultraviolet – visible spectroscopy. Ultraviolet–visible spectroscopy or UV-Vis refers to the absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region. This means it uses light in the visible and adjacent ranges. In the Folin – Ciocalteu assay, 0.1 mL of the tea infusion in gallic acid solution was mixed with 0.1 mL of the Folin – Ciocalteu reagent and 0.9 mL of water. The mixture stood for five minutes and then was added to 1.0 mL of sodium carbonate and 0.4 mL of water. The absorbance reading at 765 nm was obtained after thirty minutes. In the DPPH assay, DPPH (2,2-diphenyl-1-picryhydrazyl) solution in 2.4 mL of methanol was mixed with 0.1 mL of the tea infusion. After thirty minutes, the absorbance reading at 539 nm was obtained.    After the samples were tested, the results for the DPPH assay were tabulated in an Excel spreadsheet and a graph was created. This allowed us to determine which samples have the highest antioxidant properties among the twelve. Like the DPPH assay, the results for the Folin – Ciocalteu assay were also tabulated in an Excel spreadsheet and a graph was created. This method of data analysis allowed us to compare the phenol content of each of the samples and to observe any similarities and differences between them. Bar graphs were then created and error bars were added to display the resulting data in a more concise form. Error bars are used to indicate the error or uncertainty in a reported measurement. They provide a general idea of how precise a measurement is, or how far from the reported value the true (error free) value may be. Bar graphs were created for both antioxidant activity and phenol content of the tea samples. nce the graphs were created the data was able to be analyzed. It was found that the absorbance and emission profiles were the same for all flavors except for the rooibos blend samples (cranberry blood orange and pomegranate cherry rooibos). This may be because rooibos is an herb that is added to the tea and not a regular tea such as green tea. This herb may have different absorbance and emission profiles than regular tea. In terms of emission intensity, green teas were the strongest, followed by black teas, and then rooibos teas. The chai black tea had the highest emission among all black teas while acai berry – blueberry, tropical and jasmine had the highest emission among the green teas. The phenol content of the tea samples had ranging results. The rooibos blend samples had the lowest phenol content. The other samples had similar phenol content to each other which could indicate that different kinds of tea (green, black, etc.) do not differ drastically from one another in regards to phenol content. The antioxidant activity showed that all the flavors had almost the same antioxidant activity. This was surprising for the rooibos blend samples because they had the lowest phenol content but their antioxidant activity was comparable with the rest of the tea samples. Being that the antioxidant activity for all flavors were very close to one another, this indicated that all kinds of tea (green, black, etc.) are ‘good’ for you and all have health benefits. In conclusion, the assays used in this research study found that all the tea samples tested whether they were green tea, black tea, or rooibos blends had similar antioxidant activities which indicates that all samples have strong health benefits. When observing phenol content, the rooibos blends had the lowest phenol content which was surprising because their antioxidant activity was equivalent to the rest of the teas. The rooibos teas also showed the lowest absorbance and emission profile. This could have been due to the fact that rooibos is an herb and may have different effects when tested with these assays. Further tests on these samples would need to be done in order to make a final conclusion on the phenol content and antioxidant activity of these teas. Other antioxidant assays such as FRAP (ferric reducing ability of plasma) and ORAC (oxygen radical absorbance capacity) could be used. The antioxidant properties could also be determined at different conditions of the tea. The tea infusions could be tested after it is first made and is still hot and it could be tested when placed in a refrigerator and is cold. The hot versus cold infusions of the teas could yield different results. Finally, other tea samples could be used. Commonly used teas such as Lipton teas could be tested. Teas from a well – known company could yield similar or different results to this research study.

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