Antioxidant and cytotoxic activity of black and green tea from Vaccinium meridionale Swartz leaves

Abstract

Tea is a beverage made from leaves with high contents of polyphenolic substances that vary based on the process they are subjected to. In this study, the apical and young leaves from Vaccinium meridionale (named mortiño) were processed to obtain two kinds of tea: green and black tea. This was done in order to compare their antioxidant activity, content of secondary metabolites at different temperatures of extraction and their antiproliferative effect against SW480 colon cancer cells. Results showed that at 40°C, the green tea infusion presented higher antioxidant activity than the black tea infusion, based on their evaluation using Trolox equivalent antioxidant capacity (TEAC)-diphenylpicrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) techniques. The green tea also had maximum contents of epicatechin, caffeine, ferulic, chlorogenic and ascorbic acid than the black tea. The total contents of phenols, including hydroxycinnamic acids (caffeic and p-coumaric acid) presented similar results, in both types of tea at the same temperature, as well as the total contents of flavonoids and catechin. When temperatures increased, the extraction of bioactive compounds was more efficient in the black tea infusion than the green tea. This situation led to the increased growth rate per the temperature of the total content of phenols, among which chlorogenic, caffeic and p-coumaric acid were prominent, as well as the corresponding non-polyphenolic substances such as ascorbic acid. The latter may be responsible for the increased antioxidant activity as the temperature increased in the extraction. This antioxidant activity was observed in the black tea from mortiño leaves, using TEAC-DPPH, fluorescence recovery after photobleaching (FRAP) and ORAC assays. Both types of teas had a dose-dependent antiproliferative effect against SW480 colon adenocarcinoma cells. The IC 50 of the green and black tea was 26.3 and 36 µg/ml, respectively. These findings suggest that a tea prepared from mortiño leaves may be a promising source of antioxidant and bioactive compounds against colon cancer cells.

Effect of microwave and infrared drying over polyphenol content in Vaccinium meridionale (Swartz) dry leaves

“…In both methods it is noted that the results for FRAP assay decreases with the leaves moisture content; in the case of infrared drying shown in Figure 4a, its results were from 0.5 to 6 mg equivalent ascorbic acid/g dry leaves, which are lower than the ones obtained by microwave drying (see Figure 4b) (10-50 mg equivalent ascorbic acid/g dry leaves). It is assumed, based on the literature, that total phenols previously quantified are responsible for iron (III) reduction to iron (II) measured in this assay (Zapata-Vahos et al, 2015). This confirms that there is a better availability of the labile hydrogen proportion in polyphenols inside the dried leaves by microwave than in the ones dried by infrared.…”

“…The UV-visible spectrum was from 200 to 600 nm for all peaks. The compound's identification and quantification were done with the calibration curves for each one of the analytes desired (Zapata-Vahos et al, 2015).…”

“…Nutraceutical properties have been found for its antioxidant capacity and total polyphenol content such as in other berries (Gaviria Montoya et al, 2009). Blueberry's antioxidant capacity makes it a product with added value for neurodegenerative treatments, and in previous investigations, it was found that green tea fabrication with other parts of the plant, like leaves, makes a product with higher antioxidant activity and polyphenol content than in tea leaves (Camelia Sinensis L.) (Zapata-Vahos, Villacorta, Maldonado, Castro, & Rojano, 2015).…”

Biological Potential of Extracts of Caatinga Plants in the Control of Alternaria alternata f. sp. citri in Citrus

“…These compounds were detected in the plant species evaluated in this study, therefore, it is presumed that the antioxidant activity of their extracts is related to these substances. However, it can not be ruled out that flavonoids can act by reducing the oxidation rate in synergism with other phenolic compounds and not only attribute this property to this constituent, as verified by Zapata-Vahos et al (2015).…”

Microwave‐assisted forced convection drying effect on bioactive compounds of the Canadian blueberry leaves (Vaccinium corymbosum)

“…Antioxidants and polyphenols, being polar bioactive compounds (Figueroa et al, 2018;Gaviria Montoya et al, 2012;Oteiza et al, 2005), are sensitive to the effect of microwaves as mentioned above (Mejia-Meza et al, 2010;Śledź et al, 2013), and for that reason, the change in their antioxidant concentration due to the drying of the leaves requires a search for optimal operating conditions which allow verifying that the content of antioxidants and polyphenols is taken at the end of the drying process (Kwok et al, 2004;Madrau et al, 2009;Rabeta & Vithyia, 2013). To carry out the study of the effect of drying on the measurement of antioxidants and polyphenols at the beginning and the end of the process (Haytowitz & Bhagwat, 2010;Wijewickreme & Kitts, 1997), analytical techniques can be used such as the ferric-reducing/antioxidant power (FRAP) and total phenols (TP), reported in the literature as techniques that value the antioxidant capacity (Garzón et al, 2010;Prior et al, 1998;Wanyo et al, 2010;Wojdyło et al, 2009); and in turn, instrumental techniques such as high-performance liquid chromatography with diode-array detection (HPLC-DAD) were used to identify and quantify the presence of catechin molecules (Melgar et al, 2018;Tremocoldi et al, 2018;Wang et al, 2008a;Wang et al, 2008b); these molecules had already been reported by authors in previous writings (Gaviria et al, 2009;Isabel et al, 2015;Maldonado-Celis et al, 2014).…”