Antioxidative and anti-hydrogen peroxide activities of various herbal teas

https://doi.org/10.1016/j.foodchem.2006.08.032Get rights and content

Abstract

Herbal teas, i.e., extracts of herbs, are popular because of their fragrance and antioxidative activity. Since the antioxidative activity comes mainly from polyphenols, total polyphenol concentrations and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities in herbal teas were measured and compared. Levels of H2O2 in the teas were also examined, since the production of H2O2 in beverages such as coffee and green tea, has been reported. Only a small amount of H2O2 was detected in the herbal teas just after their preparation with hot water. However, H2O2 was gradually produced during incubation at 25 °C after extraction with hot water, especially when the teas were incubated in phosphate buffer at pH 7.4. To examine the anti-H2O2 activity of herbal teas, various teas were added to a catechin-enriched green tea, which produce much H2O2, and they were incubated at 25 °C for one day. Addition of hibiscus and thorn apple tea decreased the production of H2O2 in the catechin-enriched green tea, possibly because of a lowering of the pH of the mixture.

Introduction

Polyphenols are present in various beverages and are known to work as antioxidants (Bravo, 1998, Ina et al., 2002). Antioxidants are very important for human health, since the production of reactive oxygen species is thought to be a significant cause of aging and carcinogenesis (Beckman and Ames, 1997, Lambert and Yang, 2003). Actually, polyphenols can act as free radical-scavengers, quenching hydroxyl radicals (radical dotOH) or superoxide anion radicals (O2-) (Hanasaki et al., 1994, Sichel et al., 1991). Recent epidemiological studies have shown that flavonoid-rich foods and beverages, such as red wine, have beneficial effects on carcinogenesis and cardiovascular diseases (Soleas, Diamandis, & Goldberg, 1997).

Not only green and black tea but also various kinds of herbal teas are very popular in Japan because of their fragrance and anti-oxidative activity (Matsingou, Kapsokefaloi, & Salifoglou, 2001). These beverages are thought to be beneficial to both physical and mental health.

In contrast to the beneficial effects of polyphenols, the production of hydrogen peroxide (H2O2) from polyphenols, such as catechin derivatives, has recently been reported (Arakawa et al., 2004, Cao et al., 1997, Long et al., 1999, Nakayama et al., 2002). H2O2 was produced from polyphenol-rich beverages under quasi-physiological conditions and increased in amount with the incubation time (Akagawa et al., 2003, Chai et al., 2003). It is known that H2O2 is toxic and induces cell death in vitro (Aoshima et al., 2004, Aoshima et al., 1999, Fuchs et al., 1997, Whittermore et al., 1994). It has been reported that some polyphenols promote oxidative damage to DNA, lipids and deoxyribose under certain conditions in vitro (Hayakawa et al., 1999, Hayakawa et al., 1997, Yamanaka et al., 1997).

Various beverages in bottles are sold in vending machines in Japan. These beverages contain negligible amounts of H2O2 just after being opened, but their H2O2 levels gradually increase with time. In a previous paper, we reported methods to prevent the production of H2O2 by adding catalase or compounds which have reductive activity or which lower the pH of the beverages (Aoshima & Ayabe, 2007).

In this paper, total polyphenols (Ough & Amerine, 1988), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities (Blois, 1958) and amounts of H2O2 in various herbal teas were measured to examine the antioxidative activity and the toxicity of the teas. Then we examined the anti-H2O2 activity of herbal teas by adding them to a catechin-enriched green tea which produces H2O2.

Section snippets

Chemicals and samples

Xylenol orange, butylated hydroxytoluene (BHT), methanol and DPPH were purchased from Wako Pure Chemical Industry, Ltd., Osaka, Japan. Gallic acid was purchased from Nacalai Tesque, Kyoto, Japan. Folin and Ciocalteu’s phenol reagent was obtained from Katayama Chemical Industry, Osaka, Japan. All chemicals used were of guaranteed reagent quality. Dried herbs, rose (Rosa species), lavender (Lavandula species), chamomile (Matricaria recutita L.), hibiscus (Hibiscus sabdariffa L.), lemongrass (

Results

To examine the relationship between total polyphenol and antioxidative activity in herbal extracts, i.e., herbal teas, we measured both total polyphenol and DPPH radical-scavenging activities of herbal teas (Table 1). The correlation factor between the DPPH radical-scavenging activities and the total polyphenol concentrations was estimated to be 0.950. The pHs of the teas determined by pH test paper were: hibiscus tea, 2–3; thorn apple tea, 3–4; echinacea tea, 6–7 and other teas, 5–6.

Discussion

Polyphenols in beverages are popular because of their beneficial physiological effects on health (Bravo, 1998, Ina et al., 2002). So total polyphenol concentrations in herbal teas were measured by the Folin method and compared with their DPPH radical-scavenging activities. As expected, they showed a close relationship (correlation factor 0.950). The total polyphenol and DPPH radical-scavenging activity of rose tea were greater than those of green tea, possibly because of the presence of

Conclusions

Both the total polyphenol concentration and DPPH radical-scavenging activities of various herbal teas were measured and found to have a close correlation. Production of H2O2 in herbal teas was very low but became high at pH 7.4. Addition of hibiscus and thorn apple teas to catechin-enriched green tea prevented the production of H2O2 dose-dependently, possibly because of a decrease in the pH of the mixture.

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