1 Introduction

Rooibos tea, derived from the South African plant Aspalathus linearis, is a popular herbal beverage known for its distinctive red color and rich flavor. With a history dating back hundreds of years, it has deep cultural roots in South Africa. As trade and global cultural exchange progressed, rooibos tea spread worldwide, becoming a beloved beverage among consumers. In South Africa, rooibos tea is not only a daily drink but also carries significant social and cultural meanings, making it an integral part of South African life.

Rooibos tea is widely popular globally and is highly praised for its various health benefits.The primary bioactive compound in rooibos tea is aspalathin, a rare dietary dihydrochalcone, which has been extensively studied for its potent antioxidant properties (Johnson et al., 2018; Chaudhary et al., 2021). In addition to aspalathin, rooibos tea contains a variety of other phenolic compounds that contribute to its health-promoting effects, including anti-inflammatory, antidiabetic, and cardioprotective activities (McKay and Blumberg, 2007; Smith and Swart, 2018; Fantoukh et al., 2019).

Rooibos tea has a deep-rooted history in South African culture, particularly among the indigenous Khoisan people who have used it for its medicinal properties for centuries. The plant is endemic to the Cederberg region of the Western Cape, where it thrives in the unique climate and soil conditions. Traditionally, rooibos was harvested, fermented, and dried to produce the tea, which was then used to treat a variety of ailments, including digestive issues and skin problems (McKay and Blumberg, 2007; Marnewick et al., 2009). Over time, the popularity of rooibos tea has grown beyond South Africa, and it is now enjoyed worldwide as a caffeine-free alternative to traditional teas (Marnewick et al., 2005).

This study aims to comprehensively evaluate the antioxidant properties, health impacts, and economic effects of rooibos tea in the global market. By summarizing the current scientific evidence on the antioxidant properties of rooibos tea and its main active compound, aspalathin, we assess the health benefits associated with rooibos tea consumption, including its potential role in the prevention and management of chronic diseases such as cardiovascular disease, diabetes, and cancer. Additionally, this study explores the economic impact of rooibos tea, focusing on its market growth, global demand, and industry challenges. This study provides a more comprehensive understanding of the multifaceted benefits of rooibos tea, highlighting its significance in both health and economic contexts.

2 Phytochemistry and Antioxidant Properties

2.1 Key phytochemicals in rooibos tea

Rooibos tea (Aspalathus linearis) is renowned for its rich phytochemical profile, which includes a variety of phenolic compounds. The primary phenolic constituents identified in rooibos tea are flavonoids, tyrosols, and phenolic acids. Among these, aspalathin and nothofagin are particularly notable as they are rare dietary dihydrochalcones found predominantly in rooibos (McKay and Blumberg, 2007; Damiani et al., 2019). Other significant flavonoids include isoorientin, orientin, quercetin-3-O-robinobioside, and phenylpyruvic acid glucoside (Joubert et al., 2012). Additionally, compounds such as isovitexin, vitexin, hyperoside, rutin, ferulic acid, and isoquercitrin are present in varying concentrations (Bramati et al., 2003; Joubert et al., 2012). The presence of these compounds contributes to the tea's antioxidant properties and potential health benefits.

Rooibos tea is also rich in phenolic acids, such as 4-hydroxybenzoic acid, protocatechuic acid, and vanillic acid. These phenolic compounds not only contribute to the unique flavor of rooibos tea but also possess significant antioxidant properties.

2.2 Mechanisms of antioxidant action

The antioxidant activity of rooibos tea is primarily attributed to its high content of polyphenols, which act through various mechanisms. These include scavenging free radicals, chelating metal ions, and inhibiting oxidative enzymes. Aspalathin, one of the major flavonoids in rooibos, has been shown to exhibit significant radical scavenging activity, particularly against the DPPH radical. Other phenolic compounds such as caffeic acid and quercetin also contribute to the tea's antioxidant capacity by inhibiting lipid peroxidation and enhancing the activity of antioxidant enzymes like superoxide dismutase and catalase (Marnewick et al., 2009; Xiao et al., 2020). The total antioxidant activity (TAA) of unfermented rooibos has been reported to be higher than that of fermented rooibos, indicating that the fermentation process may reduce the antioxidant potential of the tea (Bramati et al., 2003).

Notably, aspalathin in rooibos tea not only has strong antioxidant properties but also works synergistically with vitamin C to combat oxidative stress. This synergy enhances the antioxidant effectiveness of rooibos tea, making it an ideal natural antioxidant.

2.3 Comparison with other antioxidant-rich teas

When compared to other antioxidant-rich teas such as green and black tea (Camellia sinensis), rooibos tea exhibits a unique phytochemical profile and antioxidant activity. While green and black teas are rich in catechins and theaflavins, respectively, rooibos tea is distinguished by its high levels of aspalathin and nothofagin (McKay and Blumberg, 2007; Xiao et al., 2020). Studies have shown that rooibos tea has comparable, if not superior, antioxidant activities to green and black teas in certain assays. For instance, rooibos tea has been found to significantly increase plasma total antioxidant capacity in humans, similar to the effects observed with green tea (Villaño et al., 2010). Additionally, rooibos tea has demonstrated potent chemoprotective properties against oxidative stress and cancer promotion, which are comparable to those of green and black teas (Marnewick et al., 2009). However, the specific polyphenolic composition and the interactions between these compounds and biological systems may result in different health outcomes.

Compared to other teas, rooibos tea has several additional advantages. For example, rooibos tea is caffeine-free and oxalate-free, making it more suitable for specific groups such as pregnant women, breastfeeding mothers, and individuals prone to kidney stones. Additionally, rooibos tea has a mild flavor with a unique sweetness, making it more palatable and widely accepted by the general public.

In summary, rooibos tea's rich phytochemical composition and robust antioxidant properties make it a valuable beverage for promoting health. Its unique phenolic profile, particularly the presence of aspalathin and nothofagin, sets it apart from other teas and contributes to its potential health benefits.

3 Health Implications of Rooibos Tea

3.1 Cardiovascular health benefits

Due to its rich polyphenol content, South African rooibos tea has been extensively studied for its potential benefits to cardiovascular health. The unique flavonoid aspalathin found in rooibos tea has been shown to enhance the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), thereby protecting cardiomyocytes from damage induced by hyperglycemia (Dludla et al., 2017) (Figure 1). Additionally, rooibos tea has demonstrated cardioprotective effects in diabetic cardiomyopathy by reducing oxidative stress and apoptosis in cardiomyocytes (Dludla et al., 2014). The bioactivity of rooibos tea encompasses multiple therapeutic targets, including antioxidant, anti-inflammatory, and antidiabetic effects, all of which contribute to its potential in preventing cardiovascular diseases (Smith and Swart, 2018).

Dludla et al. (2017) found that polyphenols in rooibos tea, such as aspalathin, can activate the Nrf2 pathway, increase the expression of antioxidant enzymes, and alleviate oxidative stress on the cardiovascular system. Figure 1 explains the role of Nrf2 in responding to increased reactive oxygen species (ROS) in a diabetic heart. This illustrates the potential mechanism of rooibos tea in improving cardiovascular health. By reducing ROS production and promoting its clearance, rooibos tea can effectively prevent cardiovascular diseases associated with diabetes.

3.2 Anti-inflammatory and Immune-boosting properties

Rooibos tea is known for its potent anti-inflammatory properties, which are largely attributed to its high aspalathin content. Aspalathin has been reported to possess anti-inflammatory, antimutagenic, and xanthine oxidase inhibitory activities, making it a valuable natural ingredient for various health applications (Chaudhary et al., 2021). The anti-inflammatory effects of rooibos are further supported by its ability to modulate immune system responses and adrenal steroidogenesis, which can help in managing chronic inflammatory conditions (Smith and Swart, 2018). Studies have also highlighted the immune-modulating and chemopreventive actions of rooibos, indicating its potential in enhancing overall immune health (McKay and Blumberg, 2007).

At the same time, specific components in rooibos tea can stimulate the immune system's response, helping the body to fend off viral and bacterial invasions. This immune-boosting property makes rooibos tea an ideal daily beverage, especially during cold seasons or when the immune system is weakened.

3.3 Effects on metabolic health and diabetes management

Rooibos tea has shown significant potential in managing metabolic health and diabetes. The antioxidant compounds in rooibos, such as aspalathin, have been effective in reducing oxidative stress and advanced glycation end-products (AGEs) in diabetic models, thereby preventing diabetic vascular complications (Uličná et al., 2006). Rooibos tea has also been found to improve glucose and lipid metabolism, which are critical factors in managing metabolic syndrome and type 2 diabetes (Muller et al., 2018). Furthermore, rooibos tea has demonstrated the ability to inhibit intestinal glucose absorption and enhance muscle glucose uptake, making it a functional food for diabetes management (Xiao et al., 2020).

In addition to the ability of antioxidants in rooibos tea to stabilize blood sugar levels and reduce blood sugar fluctuations, specific components in rooibos tea can also improve insulin resistance, which is significant for the prevention and management of diabetes. For diabetic patients, moderate consumption of rooibos tea may help better control blood sugar levels and reduce the risk of complications.

4 Economic Impact in the Global Market

4.1 Rooibos tea production and export

Rooibos tea, derived from the plant Aspalathus linearis and also known as rooibos or red bush tea, is a unique caffeine-free herbal beverage native to South Africa, often referred to as one of the "Three Treasures of South Africa" alongside gold and diamonds. Rooibos tea is an important component of the global herbal tea market, accounting for about 10% of the industry (Sishi et al., 2019). The production of this tea is primarily concentrated in the Western Cape province of South Africa, particularly in the Cederberg region. In recent years, with the increasing global demand for healthy beverages, the production and export volumes of rooibos tea have been steadily growing.

The production of rooibos tea is primarily concentrated in the Western Cape province of South Africa, where it is cultivated and processed before being exported worldwide. The global influence of rooibos tea has significantly expanded, and it is now sold in 37 countries, including major markets such as Germany, the Netherlands, the United Kingdom, Japan, and the United States (Joubert and Beer, 2011). This international demand underscores the value of rooibos tea as an important export commodity for South Africa.

4.2 Market demand and consumer trends

The popularity of rooibos tea is driven by its unique health benefits, including its caffeine-free nature and low tannin content, which appeal to health-conscious consumers (Joubert and Beer, 2011). Additionally, the tea's antioxidant properties contribute to its growing demand (McKay and Blumberg, 2007; Damiani et al., 2019). The market has also seen the introduction of green rooibos, an unfermented variant that offers a different flavor profile and potentially higher health benefits due to its higher polyphenol content (Joubert and Beer, 2011). Consumer trends indicate a preference for natural and health-promoting beverages, which has bolstered the market for rooibos tea. Furthermore, the rise of Fair Trade networks has connected South African producers with international markets, particularly in the United States, enhancing the visibility and appeal of rooibos tea (Raynolds and Ngcwangu, 2010).

4.3 Economic benefits for producing regions

The economic impact of rooibos tea production extends beyond mere export revenues. It plays a crucial role in the socio-economic development of the Western Cape region. The cultivation and processing of rooibos tea provide employment opportunities and support local economies (Raynolds and Ngcwangu, 2010). Fair Trade initiatives have been particularly beneficial, empowering small-scale black producers and promoting sustainable development in post-Apartheid South Africa (Raynolds and Ngcwangu, 2010). These initiatives have enabled cooperatives to upgrade their operations, including processing and packaging, thereby adding value to the product and increasing their share of the global market. The economic stability provided by the rooibos tea industry is vital for the region, especially in the face of challenges such as climate change, which threatens production areas (Sishi et al., 2019).

The global market for rooibos tea is robust and growing, driven by consumer demand for health-promoting beverages and supported by Fair Trade networks that enhance the economic benefits for South African producers. The continued expansion of this market holds significant promise for the economic development of the Western Cape region and the sustainability of rooibos tea production.

5 Genetic and Environmental Factors Affecting Quality

The quality of rooibos tea, derived from the plant Aspalathus linearis, is influenced by a complex interplay of genetic diversity and environmental conditions. These factors significantly impact the chemical composition, sensory attributes, and overall quality of the tea.

5.1 Genetic diversity and its impact on quality

Genetic diversity within rooibos plants contributes to variations in phenolic compounds, which are critical for the tea's antioxidant properties and overall quality. Studies have shown that different ecotypes of rooibos exhibit varying levels of these phenolic compounds due to genetic differences. For instance, research indicates that the major phenolic constituents such as aspalathin, nothofagin, and isoquercitrin vary significantly among different rooibos plants (Figure 2) (Stander et al., 2020). This genetic variation affects the antioxidant capacity and health benefits of the tea.

Stander et al. (2020) studied the diversity of thin-layer chromatography (TLC) banding patterns in various rooibos tea samples (Figure 2). They found that bands 1-6 were commonly observed in both commercial and wild rooibos tea samples, while bands A and B were only found in selected plants. The study revealed significant differences in the presence of major phenolic compounds among different rooibos tea plants. These findings emphasize the importance of genetic diversity in rooibos tea plants and its significant impact on their chemical composition. The unique phenolic compounds found in specific plants may offer new avenues for enhancing the antioxidant properties and health benefits of rooibos tea.

5.2 Environmental influences on chemical composition

Environmental factors, including soil quality, temperature, and seasonal variations, play a crucial role in determining the chemical composition of rooibos tea. Soil quality, for instance, has been found to influence the phenolic content and overall yield of rooibos plants. Poor soil conditions, such as those with low organic matter and essential nutrients, can lead to decreased yields and lower quality tea (Smith et al., 2017).

Temperature also significantly affects the growth and phenolic content of rooibos plants. Elevated temperatures can lead to stress responses in plants, altering their phenolic profiles and potentially reducing tea quality (MacAlister et al., 2020). Additionally, the production season impacts the phenolic content of the tea, with variations observed across different seasons (Stanimirova et al., 2013).

5.3 Interaction between genetics and environment

The interaction between genetic factors and environmental conditions further complicates the quality of rooibos tea. For example, specific genetic variants of rooibos may respond differently to environmental stresses, resulting in varied phenolic profiles and tea quality. Research indicates that fermentation and drying conditions significantly impact the quality of rooibos tea, with both genetic and environmental factors contributing to these effects (Yang et al., 2020).

The quality of rooibos tea is determined by a dynamic interplay of genetic diversity and environmental influences. Understanding these factors can help in optimizing cultivation practices to enhance the quality and health benefits of rooibos tea.

6 Case Studies

6.1 Antioxidant properties of fermented rooibos tea

Fermented rooibos tea is known for its distinctive reddish-brown color and has been widely studied for its antioxidant properties (Figure 3), while unfermented rooibos tea retains a green color (Dludla et al., 2017). The fermentation process affects the polyphenol content, which in turn influences the tea's antioxidant capacity.

Studies have shown that fermented rooibos tea contains a variety of polyphenols, including aspalathin and nothofagin, which contribute to its antioxidant activity (McKay and Blumberg, 2007; Moosa et al., 2018). The total antioxidant activity (TAA) of fermented rooibos is lower compared to unfermented rooibos, yet it still exhibits significant radical scavenging properties (Bramati et al., 2003; Moosa et al., 2018). Additionally, fermented rooibos has been found to inhibit osteoclast formation and activity, which is beneficial for bone health, potentially due to its antioxidant properties (Moosa et al., 2018). The consumption of fermented rooibos has also been linked to improved lipid profiles and reduced oxidative stress markers in adults at risk for cardiovascular disease, further highlighting its health benefits (Marnewick et al., 2011).

6.2 Health benefits of unfermented rooibos tea

Unfermented rooibos tea, often referred to as "green" rooibos, retains a higher content of flavonoids compared to its fermented counterpart. This higher flavonoid content translates to a greater total antioxidant activity, which is approximately twice that of fermented rooibos (Bramati et al., 2003). Unfermented rooibos has been shown to significantly increase plasma total antioxidant capacity in healthy humans, indicating its potential to enhance the body's defense against oxidative stress (Villaño et al., 2010). Moreover, unfermented rooibos has demonstrated neuroprotective and anxiolytic properties, making it a promising candidate for functional brain food and nutraceutical development (López et al., 2021). The tea's ability to inhibit key enzymes of the central nervous system, such as monoamine oxidase A (MAO-A), further supports its potential in promoting mental health (López et al., 2021). Additionally, unfermented rooibos has been found to offer chemoprotective properties against cancer promotion in rat liver models, suggesting its role in cancer prevention (Marnewick et al., 2009).

6.3 Economic impact on south african economy

Rooibos tea, both fermented and unfermented, plays a significant role in the South African economy. The global demand for rooibos has been steadily increasing, driven by its recognized health benefits and unique flavor profile. Rooibos is indigenous to the Western Cape province of South Africa, and its cultivation and processing provide employment opportunities and contribute to the local economy (Moosa et al., 2018). The export of rooibos tea has positioned South Africa as a key player in the global herbal tea market, with economic benefits extending to various sectors, including agriculture, manufacturing, and tourism. The growing popularity of rooibos tea worldwide underscores its economic importance and potential for further market expansion (McKay and Blumberg, 2007; Fantoukh et al., 2019). The sustainable cultivation practices and the unique geographical indication status of rooibos also enhance its market value and contribute to the economic stability of the region (McKay and Blumberg, 2007).

7 Applications and Future Directions

7.1 Health applications of rooibos tea

Rooibos tea (Aspalathus linearis) has garnered significant attention for its potential health benefits, primarily attributed to its rich polyphenolic content. Studies have demonstrated that rooibos tea exhibits potent antioxidant properties, which can mitigate oxidative stress and related health issues. For instance, research has shown that rooibos tea can partially prevent oxidative stress in streptozotocin-induced diabetic rats, suggesting its potential as an adjuvant in managing diabetic complications (Uličná et al., 2006). Additionally, rooibos tea has been found to increase plasma total antioxidant capacity in healthy humans, indicating its role in enhancing the body's defense against oxidative damage (Villaño et al., 2010). The bioavailability of rooibos flavonoids in humans further supports its health benefits, as metabolites of key flavonoids like aspalathin and nothofagin have been detected in plasma and urine following consumption (Breiter et al., 2011). Moreover, rooibos tea has shown chemoprotective properties against cancer promotion in rat liver, highlighting its potential in cancer prevention (Marnewick et al., 2009).

7.2 Potential industrial uses

Beyond its health applications, rooibos tea holds promise for various industrial uses. The phenolic profile and antioxidant capacity of rooibos tea can be leveraged in the food and beverage industry to develop functional foods and nutraceuticals. The identification of potential antioxidant markers through chromatographic fingerprints can aid in quality control and standardization of rooibos tea products (Orzel et al., 2014). Additionally, the antioxidant and antimutagenic potentials of rooibos tea at different processing stages suggest its utility in developing natural preservatives and additives for food products (Standley et al., 2001). The diverse polyphenolic composition of rooibos tea, including compounds like ferulic acid, quercetin, and rutin, further expands its application in the cosmetic and pharmaceutical industries, where these compounds can be used for their anti-inflammatory and skin-protective properties (Epure et al., 2019).

7.3 Future research directions

While the current body of research underscores the health benefits and industrial potential of rooibos tea, several areas warrant further investigation. Future research should focus on conducting more extensive human clinical trials to validate the health claims associated with rooibos tea consumption. Studies exploring the long-term effects of rooibos tea on chronic diseases, such as cardiovascular diseases and cancer, are particularly needed (McKay and Blumberg, 2007; Chen et al., 2013). Additionally, research should aim to elucidate the molecular mechanisms underlying the antioxidant and anti-inflammatory effects of rooibos tea, with a focus on identifying specific bioactive compounds and their interactions with cellular pathways (Villaño et al., 2010; Damiani et al., 2019). The development of standardized extraction and processing methods to preserve the bioactive compounds in rooibos tea is another critical area for future research. Finally, exploring the economic impact of rooibos tea in the global market, including its potential for sustainable agriculture and trade, can provide valuable insights for stakeholders and policymakers (McKay and Blumberg, 2007).

8 Challenges and Opportunities

8.1 Technical challenges in rooibos tea research

Rooibos tea research faces several technical challenges, particularly in the standardization of its antioxidant properties and the variability in its phenolic content. The phenolic profile and antioxidant capacity of rooibos tea can be significantly influenced by the brewing method, as demonstrated by the differences observed between cold brewing, regular brewing, and microwave boiling (Damiani et al., 2019). Additionally, the variability in phenolic content due to production seasons and quality grades further complicates the standardization process (Joubert et al., 2012). The identification and quantification of individual phenolic compounds using advanced chromatographic techniques, such as HPLC and UHPLC-QTOF mass spectrometry, are essential but require sophisticated equipment and expertise (Orzel et al., 2014; Epure et al., 2019). Moreover, the lack of extensive human studies limits the understanding of the health benefits and potential adverse effects of rooibos tea consumption (McKay and Blumberg, 2007).

8.2 Opportunities for market expansion

The global market for rooibos tea presents numerous opportunities for expansion. The growing awareness of its health benefits, particularly its antioxidant properties, positions rooibos tea as a desirable product in the health and wellness sector (McKay and Blumberg, 2007; Villaño et al., 2010). The unique phenolic composition of rooibos tea, including rare compounds like aspalathin and nothofagin, offers a competitive edge over other herbal teas (McKay and Blumberg, 2007). Additionally, the increasing demand for natural and organic products provides an opportunity for rooibos tea producers to market their products as premium, health-promoting beverages. The versatility of rooibos tea, which can be consumed both hot and cold, further enhances its market appeal (Damiani et al., 2019). Collaborations with health and wellness influencers and the development of innovative rooibos-based products, such as supplements and skincare items, can also drive market growth.

8.3 Potential for improving quality and production

Improving the quality and production of rooibos tea involves addressing the variability in its phenolic content and antioxidant capacity. Research has shown that the antioxidant capacity of rooibos tea can be predicted from its chromatographic fingerprints, allowing for the identification of potential antioxidant markers (Orzel et al., 2014). This approach can be utilized in quality control to ensure consistent product quality. Additionally, optimizing the brewing conditions to maximize the extraction of beneficial phenolic compounds can enhance the health benefits of rooibos tea (Damiani et al., 2019). The development of standardized cultivation and processing methods, taking into account the impact of production seasons and quality grades, can further improve the consistency and quality of rooibos tea (Joubert et al., 2012). Investment in research and development to explore the full potential of rooibos tea's bioactive compounds and their health implications can also contribute to the advancement of the industry (Uličná et al., 2006; Awoniyi et al., 2012).

9 Concluding Remarks

This study highlights the significant antioxidant properties of South African black tea, mainly attributed to its rich phenolic compound composition. Various studies have demonstrated that both fermented and unfermented rooibos teas possess potent antioxidant capacities, with unfermented rooibos generally showing higher levels of flavonoids and total antioxidant activity compared to fermented rooibos. The bioavailability of these flavonoids in humans has been confirmed, although their plasma concentrations are relatively low. Additionally, rooibos tea has been shown to increase plasma total antioxidant capacity in healthy humans, and it offers protective effects against oxidative stress in animal models. The antioxidant activity of rooibos tea has been compared favorably with other well-known antioxidants such as α-tocopherol and BHT.

Research has found that the rooibos tea industry has multiple impacts. The proven health benefits, particularly its antioxidant properties, can be leveraged in marketing strategies to promote rooibos tea as a healthful beverage. The industry can also explore developing new products that maximize the retention of these beneficial compounds, such as cold-brewed or minimally processed rooibos tea. Additionally, the absence of adverse effects in human studies supports the safety of rooibos tea consumption, which can be emphasized to reassure consumers. The industry should also consider investing in further research to substantiate health claims and explore additional health benefits, potentially opening new market opportunities.

Future research should focus on conducting more extensive human studies to better understand the health benefits of rooibos tea and its bioactive compounds. There is a need for long-term clinical trials to confirm the antioxidant and other health-promoting effects observed in vitro and in animal models. Additionally, exploring the impact of different preparation methods on the phenolic profile and antioxidant capacity of rooibos tea could provide valuable insights for optimizing its health benefits. The identification and validation of specific antioxidant markers could also enhance quality control measures within the industry. Finally, investigating the economic impact of rooibos tea in the global market, including its potential for growth and challenges, would provide a comprehensive understanding of its market dynamics and inform strategic decisions for stakeholders.

Acknowledgments

The author expresses deep gratitude to the peer reviewers for their invaluable guidance on the manuscript of this study.

Conflict of Interest Disclosure

The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

Reference

Awoniyi D., Aboua Y., Marnewick J., and Brooks N., 2012, The effects of rooibos (Aspalathus linearis), green tea (Camellia sinensis) and commercial rooibos and green tea supplements on epididymal sperm in oxidative stress‐induced rats, Phytotherapy Research, 26(8): 1231-1239

https://doi.org/10.1002/ptr.3717

PMid:22228422

Bramati L., Aquilano F., and Pietta P., 2003, Unfermented rooibos tea: quantitative characterization of flavonoids by HPLC-UV and determination of the total antioxidant activity, Journal of agricultural and food chemistry, 51(25): 7472-7474.

https://doi.org/10.1021/jf0347721

PMid:14640601

Breiter T., Laue C., Kressel G., Gröll S., Engelhardt U., and Hahn A., 2011, Bioavailability and antioxidant potential of rooibos flavonoids in humans following the consumption of different rooibos formulations, Food Chemistry, 128(2) 338-347.

https://doi.org/10.1016/j.foodchem.2011.03.029

PMid:25212140

Chaudhary S., Sandasi M., Makolo F., Heerden F., and Viljoen A., 2021, Aspalathin: a rare dietary dihydrochalcone from Aspalathus linearis (rooibos tea), Phytochemistry Reviews, 20: 1161-1192.

https://doi.org/10.1007/s11101-021-09741-9

Chen W., Sudji I., Wang E., Joubert E., Wyk B., and Wink M., 2013, Ameliorative effect of aspalathin from rooibos (Aspalathus linearis) on acute oxidative stress in Caenorhabditis elegans, Phytomedicine: International Journal of Phytotherapy and Phytopharmacology, 20(3-4): 380-386.

https://doi.org/10.1016/j.phymed.2012.10.006

PMid:23218401

Damiani E., Carloni P., Rocchetti G., Senizza B., Tiano L., Joubert E., Beer D., and Lucini L., 2019, Impact of cold versus hot brewing on the phenolic profile and antioxidant capacity of rooibos (Aspalathus linearis) herbal tea, Antioxidants, 8(10): 499.

https://doi.org/10.3390/antiox8100499

PMid:31640245 PMCid:PMC6826389

Dludla P., Dludla P., Muller C., Louw J., Joubert E., Salie R., Salie R., Opoku A., and Johnson R., 2014, The cardioprotective effect of an aqueous extract of fermented rooibos (Aspalathus linearis) on cultured cardiomyocytes derived from diabetic rats, Phytomedicine: International Journal of Phytotherapy and Phytopharmacology, 21(5): 595-601.

https://doi.org/10.1016/j.phymed.2013.10.029

PMid:24268738

Dludla P., Joubert E., Muller C., Louw J., and Johnson R,. 2017, Hyperglycemia-induced oxidative stress and heart disease-cardioprotective effects of rooibos flavonoids and phenylpyruvic acid-2-O-β-D-glucoside, Nutrition & Metabolism, 14: 45.

https://doi.org/10.1186/s12986-017-0200-8

PMid:28702068 PMCid:PMC5504778

Epure A., Oniga I., Benedec D., Hanganu D., Gheldiu A.M., Toiu A., and Vlase L., 2019, Chemical analysis and antioxidant activity of some rooibos tea products, Farmacia, 67(6).

https://doi.org/10.31925/farmacia.2019.6.5

Fantoukh O., Dale O., Parveen A., Hawwal M., Ali Z., Manda V., Khan S., Chittiboyina A., Viljoen A., and Khan I., 2019, Safety assessment of phytochemicals derived from the globalized South African rooibos tea (Aspalathus linearis) through Interaction with CYP, PXR, and P-gp, Journal of agricultural and food chemistry, 67(17): 4967-4975.

https://doi.org/10.1021/acs.jafc.9b00846

PMid:30955332

Johnson R., Beer D., Dludla P., Ferreira D., Muller C., and Joubert E., 2018, Aspalathin from rooibos (Aspalathus linearis): a bioactive C-glucosyl dihydrochalcone with potential to target the metabolic syndrome, Planta Medica, 84: 568-583.

https://doi.org/10.1055/s-0044-100622

PMid:29388183

Joubert E., and Beer D., 2011, Rooibos (Aspalathus linearis) beyond the farm gate: From herbal tea to potential phytopharmaceutical, South African Journal of Botany, 77: 869-886.

https://doi.org/10.1016/j.sajb.2011.07.004

Joubert E., Beelders T., Beer D., Malherbe C., Villiers A., and Sigge G., 2012, Variation in phenolic content and antioxidant activity of fermented rooibos herbal tea infusions: role of production season and quality grade, Journal of Agricultural and Food Chemistry, 60(36): 9171-9179.

https://doi.org/10.1021/jf302583r

PMid:22920220

López V., Cásedas G., Petersen-Ross K., Powrie Y., and Smith C., 2021, Neuroprotective and anxiolytic potential of green rooibos (Aspalathus linearis) polyphenolic extract, Food & Function, 13: 91-101

https://doi.org/10.1039/D1FO03178C

PMid:34877951

MacAlister D., Muasya A., Crespo O., Ogola J., Maseko S., Valentine A., Ottosen C., Rosenqvist E., and Chimphango S., 2020, Effect of temperature on plant growth and stress tolerant traits in rooibos in the Western Cape, South Africa, Scientia Horticulturae, 263: 109137.

https://doi.org/10.1016/j.scienta.2019.109137

Marnewick J., Joubert E., Joseph S., Swanevelder S., Swart P., and Gelderblom W., 2005, Inhibition of tumour promotion in mouse skin by extracts of rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia), unique South African herbal teas, Cancer letters, 224(2): 193-202.

https://doi.org/10.1016/j.canlet.2004.11.014

PMid:15914270

Marnewick J., Rautenbach F., Venter I., Neethling H., Blackhurst D., Wolmarans P., and Macharia M., 2011, Effects of rooibos (Aspalathus linearis) on oxidative stress and biochemical parameters in adults at risk for cardiovascular disease, Journal of Ethnopharmacology, 133(1): 46-52.

https://doi.org/10.1016/j.jep.2010.08.061

PMid:20833235

Marnewick J., Westhuizen F., Joubert E., Swanevelder S., Swart P., and Gelderblom W., 2009, Chemoprotective properties of rooibos (Aspalathus linearis), honeybush (Cyclopia intermedia) herbal and green and black (Camellia sinensis) teas against cancer promotion induced by fumonisin B1 in rat liver, Food and Chemical Toxicology: An International Journal Published for the British Industrial Biological Research Association, 47(1): 220-229.

https://doi.org/10.1016/j.fct.2008.11.004

PMid:19041360

McKay D., and Blumberg J., 2007, A review of the bioactivity of south African herbal teas: rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia), Phytotherapy Research, 21(1): 1-16.

https://doi.org/10.1002/ptr.1992

PMid:16927447

Moosa S., Kasonga A., Deepak V., Marais S., Magoshi I., Bester M., Kruger M., and Coetzee M., 2018, Rooibos tea extracts inhibit osteoclast formation and activity through the attenuation of NF-κB activity in RAW264.7 murine macrophages, Food & Function, 9(6): 3301-3312.

https://doi.org/10.1039/C7FO01497J

PMid:29790498

Muller C., Malherbe C., Chellan N., Yagasaki K., Miura Y., and Joubert E., 2018, Potential of rooibos, its major C-glucosyl flavonoids, and Z-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid in prevention of metabolic syndrome, Critical Reviews in Food Science and Nutrition, 58: 227-246.

https://doi.org/10.1080/10408398.2016.1157568

PMid:27305453

Orzel J., Daszykowski M., Kazura M., Beer D., Joubert E., Schulze A., Beelders T., Villiers A., Malherbe C., and Walczak B., 2014, Modeling of the total antioxidant capacity of rooibos (Aspalathus linearis) tea infusions from chromatographic fingerprints and identification of potential antioxidant markers, Journal of Chromatography., A, 1366: 101-109.

https://doi.org/10.1016/j.chroma.2014.09.030

PMid:25283576

Raynolds L., and Ngcwangu S., 2010, Fair trade rooibos tea: connecting South African producers and American consumer markets, Geoforum, 41: 74-83.

https://doi.org/10.1016/j.geoforum.2009.02.004

Sishi M., Muller M., Beer D., Rijst M., and Joubert E., 2019, Rooibos agro-processing waste as herbal tea products: optimisation of soluble solids extraction from dust and application to improve sensory profile, colour and flavonoid content of stem infusions, Journal of the Science of Food and Agriculture, 99(7): 3653-3661.

https://doi.org/10.1002/jsfa.9587

PMid:30637751

Smith C., and Swart A., 2018, Aspalathus linearis (Rooibos)-a functional food targeting cardiovascular disease, Food & Function, 9(10): 5041-5058.

https://doi.org/10.1039/C8FO01010B

PMid:30183052

Smith J., Botha A., and Hardie A., 2017, Role of soil quality in declining rooibos (Aspalathus linearis) tea yields in the Clanwilliam area, South Africa, Soil Research, 56: 252-263.

https://doi.org/10.1071/SR17029

Stander E., Williams W., Mgwatyu Y., Heusden P., Rautenbach F., Marnewick J., Roes-Hill M., and Hesse U., 2020, Transcriptomics of the rooibos (Aspalathus linearis) species complex, BioTech, 9(4): 19

https://doi.org/10.3390/biotech9040019

PMid:35822822 PMCid:PMC9258316

Standley L., Winterton P., Marnewick J., Gelderblom W., Joubert E., and Britz T., 2001, Influence of processing stages on antimutagenic and antioxidant potentials of rooibos tea, Journal of Agricultural and Food Chemistry, 49(1): 114-117.

https://doi.org/10.1021/jf000802d

PMid:11170567

Stanimirova I., Kazura M., Beer D., Joubert E., Schulze A., Beelders T., Villiers A., and Walczak B., 2013, High-dimensional nested analysis of variance to assess the effect of production season, quality grade and steam pasteurization on the phenolic composition of fermented rooibos herbal tea, Talanta, 115: 590-599.

https://doi.org/10.1016/j.talanta.2013.06.023

PMid:24054637

Uličná O., Vančová O., Boz̆ek P., Čársky J., Šebeková K., Boor P., Nakano M., and Greksák M., 2006, Rooibos tea (Aspalathus linearis) partially prevents oxidative stress in streptozotocin-induced diabetic rats, Physiological research, 55(2): 157-164.

https://doi.org/10.33549/physiolres.930778

PMid:15910170

Villaño D., Pecorari M., Testa M., Raguzzini A., Stalmach A., Crozier A., Tubili C., and Serafini M., 2010, Unfermented and fermented rooibos teas (Aspalathus linearis) increase plasma total antioxidant capacity in healthy humans, Food Chemistry, 123: 679-683.

https://doi.org/10.1016/j.foodchem.2010.05.032

Xiao X., Erukainure O., Sanni O., Koorbanally N., and Islam M., 2020, Phytochemical properties of black tea (Camellia sinensis) and rooibos tea (Aspalathus linearis); and their modulatory effects on key hyperglycaemic processes and oxidative stress, Journal of Food Science and Technology, 57: 4345-4354.

https://doi.org/10.1007/s13197-020-04471-w

PMid:33087948 PMCid:PMC7550481

Yang C., Zhao Y., Ting A., Zhongyuan L., Jiang Y., Li Y., and Chunwang D., 2021, Quantitative prediction and visualization of key physical and chemical components in black tea fermentation using hyperspectral imaging, Lwt-Food Science and Technology, 141: 110975.

https://doi.org/10.1016/j.lwt.2021.110975