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Anti-peroxyl radical quality and antibacterial properties of rooibos infusions and their pure glycosylated polyphenolic constituents.

Simpson MJ, Hjelmqvist D, López-Alarcón C, Karamehmedovic N, Minehan TG, Yepremyan A, Salehani B, Lissi E, Joubert E, Udekwu KI, Alarcon EI - Molecules (2013)

Bottom Line: The anti-peroxyl radical quality of two aqueous rooibos infusions and solutions of their most abundant glycosylated polyphenols was evaluated using pyrogallol red and fluorescein-based oxygen radical absorbance ratios.Additionally, the antimicrobial activity of the natural and artificial infusions was assessed against three species of bacteria: Gram (+) Staphylococus epidermidis and Staphylococcus aureus and Gram (-) Escherichia coli.When compared to the natural infusions the artificial beverages did not demonstrate any bacterostatic/cidal activity, suggesting that the antibacterial activity of rooibos is related to compounds other than the glycosylated polyphenols employed in our study.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, ON K1N6N5, Canada.

ABSTRACT
The anti-peroxyl radical quality of two aqueous rooibos infusions and solutions of their most abundant glycosylated polyphenols was evaluated using pyrogallol red and fluorescein-based oxygen radical absorbance ratios. It was observed that the artificial infusions, prepared using only the most abundant polyphenols present in rooibos and at concentrations similar to those found in the natural infusions, showed greater antioxidant quality than the latter infusions, reaching values close to those reported for tea infusions. Additionally, the antimicrobial activity of the natural and artificial infusions was assessed against three species of bacteria: Gram (+) Staphylococus epidermidis and Staphylococcus aureus and Gram (-) Escherichia coli. When compared to the natural infusions the artificial beverages did not demonstrate any bacterostatic/cidal activity, suggesting that the antibacterial activity of rooibos is related to compounds other than the glycosylated polyphenols employed in our study.

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Chemical structures and atom labeling for the polyphenols of rooibos employed in this study classified according their chemical structures. Note that only aspalathin is uniquely found in rooibos.
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Figure 4: Chemical structures and atom labeling for the polyphenols of rooibos employed in this study classified according their chemical structures. Note that only aspalathin is uniquely found in rooibos.

Mentions: Infusions of the herbal tea rooibos (Aspalathus linearis, a plant endemic to the Western Cape Province of South Africa) are caffeine-free, low-tannin beverages [21,22] that are a source of uncommon glycosylated polyphenol compounds (Scheme 1) [23–25]. It has been reported that the antioxidant activity of natural rooibos infusions and extracts depends on the total polyphenol content of the sample, which is determined by how the plant is processed [26–28]. In contrast to the polyphenol compounds present in black tea, such as the flavanols epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate [1], rooibos infusions contain glycosylated polyphenols (flavonoids) including the unique dihydrochalcone, aspalathin (Asp). The anti/pro-oxidant performance of aqueous extracts of fermented and unfermented rooibos against linoleic acid and deoxyribose oxidation is directly related to their Asp content [29]. The reactivity of Asp against DPPH and superoxide anion radicals is greater than that of Trolox and similar to that of quercetin [30]. On the other hand, the ability of Asp to prevent β-carotene oxidation is considerably lower than that displayed by either α-tocopherol or quercetin [31]. The induction times become one order of magnitude larger when measured using the Rancimat method [31]. The effectiveness of these glycosylated polyphenols against reactive radical species that are directly involved in causing oxidative stress within living organisms remains unknown [32]. Recently, Joubert et al. [24,33] have reported the oxygen radical scavenging capacities of rooibos infusions and extracts, using fluorescence detection (ORAC-FL). However, the antioxidant quality and the contribution of the glycosylated polyphenols to that anti-peroxyl radical scavenger ability of natural rooibos infusions are still unknown.


Anti-peroxyl radical quality and antibacterial properties of rooibos infusions and their pure glycosylated polyphenolic constituents.

Simpson MJ, Hjelmqvist D, López-Alarcón C, Karamehmedovic N, Minehan TG, Yepremyan A, Salehani B, Lissi E, Joubert E, Udekwu KI, Alarcon EI - Molecules (2013)

Chemical structures and atom labeling for the polyphenols of rooibos employed in this study classified according their chemical structures. Note that only aspalathin is uniquely found in rooibos.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4067240&req=5

Figure 4: Chemical structures and atom labeling for the polyphenols of rooibos employed in this study classified according their chemical structures. Note that only aspalathin is uniquely found in rooibos.
Mentions: Infusions of the herbal tea rooibos (Aspalathus linearis, a plant endemic to the Western Cape Province of South Africa) are caffeine-free, low-tannin beverages [21,22] that are a source of uncommon glycosylated polyphenol compounds (Scheme 1) [23–25]. It has been reported that the antioxidant activity of natural rooibos infusions and extracts depends on the total polyphenol content of the sample, which is determined by how the plant is processed [26–28]. In contrast to the polyphenol compounds present in black tea, such as the flavanols epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate [1], rooibos infusions contain glycosylated polyphenols (flavonoids) including the unique dihydrochalcone, aspalathin (Asp). The anti/pro-oxidant performance of aqueous extracts of fermented and unfermented rooibos against linoleic acid and deoxyribose oxidation is directly related to their Asp content [29]. The reactivity of Asp against DPPH and superoxide anion radicals is greater than that of Trolox and similar to that of quercetin [30]. On the other hand, the ability of Asp to prevent β-carotene oxidation is considerably lower than that displayed by either α-tocopherol or quercetin [31]. The induction times become one order of magnitude larger when measured using the Rancimat method [31]. The effectiveness of these glycosylated polyphenols against reactive radical species that are directly involved in causing oxidative stress within living organisms remains unknown [32]. Recently, Joubert et al. [24,33] have reported the oxygen radical scavenging capacities of rooibos infusions and extracts, using fluorescence detection (ORAC-FL). However, the antioxidant quality and the contribution of the glycosylated polyphenols to that anti-peroxyl radical scavenger ability of natural rooibos infusions are still unknown.

Bottom Line: The anti-peroxyl radical quality of two aqueous rooibos infusions and solutions of their most abundant glycosylated polyphenols was evaluated using pyrogallol red and fluorescein-based oxygen radical absorbance ratios.Additionally, the antimicrobial activity of the natural and artificial infusions was assessed against three species of bacteria: Gram (+) Staphylococus epidermidis and Staphylococcus aureus and Gram (-) Escherichia coli.When compared to the natural infusions the artificial beverages did not demonstrate any bacterostatic/cidal activity, suggesting that the antibacterial activity of rooibos is related to compounds other than the glycosylated polyphenols employed in our study.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, ON K1N6N5, Canada.

ABSTRACT
The anti-peroxyl radical quality of two aqueous rooibos infusions and solutions of their most abundant glycosylated polyphenols was evaluated using pyrogallol red and fluorescein-based oxygen radical absorbance ratios. It was observed that the artificial infusions, prepared using only the most abundant polyphenols present in rooibos and at concentrations similar to those found in the natural infusions, showed greater antioxidant quality than the latter infusions, reaching values close to those reported for tea infusions. Additionally, the antimicrobial activity of the natural and artificial infusions was assessed against three species of bacteria: Gram (+) Staphylococus epidermidis and Staphylococcus aureus and Gram (-) Escherichia coli. When compared to the natural infusions the artificial beverages did not demonstrate any bacterostatic/cidal activity, suggesting that the antibacterial activity of rooibos is related to compounds other than the glycosylated polyphenols employed in our study.

Show MeSH
Related in: MedlinePlus