Antioxidant activity of hot water infusions and subcritical water extracts from teas and tea-like plants

Bc. Kateřina Berková

Master's thesis

Abstract:

Oxidative stress and related non-communicable diseases are the No. 1 cause of death worldwide. It is generally said that such diseases concern mainly developed countries of the Western world, however, in recent years, they have become an emerging global problem with a growing trend in developing countries, which is often associated with the change of lifestyle and cultural norms. The main risks contributing to the spread of oxidative stress (unhealthy diet, low physical activity, smoking, alcohol misuse) and thus non-communicable diseases are preventable and can be managed on the individual level. Tea (Camellia sinensis) is the 2nd most popular beverage in the world and many other hot beverages made of different species (Aspalathus linearis, Cyclopia intermedia, Hibiscus sabdariffa) have also gained significant regional importance. They are cheap and available, and their consumption is associated with several health benefits, especially due to the high content of polyphenolic substances and other antioxidants. Nowadays we can find many food products with antioxidant content on the market. Plant extracts used for their manufacturing are often obtained by environmentally non-friendly, time-consuming, and inefficient methods. Subcritical water extraction (SWE) is known as a novel green method used for the extraction of natural products that can improve heat and mass transfer, thus increasing extraction yields and efficiency. In this study, antioxidant activity and Total phenolic content (TPC) of 5 teas and tea-like plant extracts obtained by water infusion (WI) and SWE were determined and compared. Extracts obtained by WI method showed stronger antioxidant activity and higher TPC than SWE extracts in all cases. Extract of Camellia sinensis – green tea obtained by WI was evaluated as the most promising one with the lowest IC50 of 17.22 µg/mL (DPPH) and 9.85 µg/mL (ORAC), and the highest TPC of 475.76 mg GAE/g. Even though SWE is considered a promising method for the extraction of plant material, the methodology is not uniform, especially in temperature and extraction time, which affect the extraction efficiency. For further research, it would be appropriate to optimize SWE conditions for teas and tea-like plants by collecting the extract in the form of separated fractions, or by shortening the extraction time, which may enhance the final antioxidant content.

Keywords

DPPH, Camellia sinensis, green extraction method, ORAC, Total phenolic content, traditional beverage

Language used: English

Date on which the thesis was submitted / produced: 23. 4. 2023

Thesis defence

• Date of defence: 29. 5. 2023
• Supervisor: Ing. Johana Rondevaldová, Ph.D.
• Reader: Jan Tauchen, Ph.D.

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme:
Tropical Crop Management and Ecology