Compostos bioativos de chá roxo (Camellia Sinensis var. assamica cv. Zijuan): otimização de extração, atividades biológicas, e avaliação em modelo de bebida

Abstract

In order to maximize the extraction of bioactive compounds and antioxidant activity (AA) from green tea from purple leaves of Camellia sinensis (L.) var. assamica (Mast.) Kitamura, studies were conducted to evaluate extraction methods for bioactive compounds, involving time, temperature, solvents and the proportion of plant material in the extraction process, in addition to investigating the chemical composition of the different extracts obtained, activity in vitro antioxidant, chemical stability of compounds and in vitro bioactivities. In the first study (Chapter 2), simultaneous optimization was applied, which resulted in the combination of a temperature of 60 °C, a time of 15 min and a mass-solvent ratio of 1 g of dehydrated purple leaves to 62.3 mL of solvent (ethanol/citric acid solution 80:20 v/v), as ideal extraction conditions. This lyophilized extract under ideal conditions exerted cytotoxic and antiproliferative effects against

human cell lines (IMR90, A549 and HCT8), antimicrobial activity against some Gram- negative and Gram-positive microorganisms, such as Escherichia coli (IAL 2064),

Listeria monocytogenes (ATCC 7644), Staphylococcus aureus (ATCC 13565) and Staphylococcus epidermidis and reduced the secretion of pro-inflammatory cytokines (TNF-α, CXCL2/MIP-2 and IL-6) in RAW 264.7 macrophages. Subsequently, the evaluation of the extraction solvent (Chapter 3) was conducted on green tea from purple leaves of C. sinensis, with the aim of estimating the isolated effect of the solvents, water and ethanol, and their binary combinations on the extraction of bioactive compounds. In this study, the ideal condition was obtained with a proportion of 75% ethanol and 25% water as extraction solvent. The extract in the ideal condition showed the diversity of phenolic compounds, antioxidant activity in vitro, did not show hemolytic behavior in erythrocytes subjected to hypotonic and isotonic conditions, in addition to presenting cytotoxic effects in vitro due to antioxidant and pro-oxidant activities in cancerous and hybrid cells, respectively. Finally, a last extraction condition was studied (Chapter 4), using water acidified with citric acid as the extracting solvent. This extract presented levels of different classes of phenolic compounds, in vitro antioxidant activity, reversible anthocyanin balance and antioxidant activity with pH variation. When evaluating chemical stability, photodegradation was observed after 24 h of light exposure and thermal degradation (> 80 °C). The lyophilized extract showed antioxidant properties such as inhibition of lipid peroxidation, protection of human plasma against copper-induced oxidation and reduction of cell viability, in addition to exerting antiproliferative and cytotoxic effects in cell lines (A549 HepG2, HCT8 and Eahy926). In the three studies carried out with purple leaves of C. sinensis (cv. Zijuan), the extracts obtained by a simple, low-cost process using non-toxic solvents showed high technological potential, but in vivo bioavailability and bioaccessibility studies are still lacking.