Rooibos tea or Red Bush tea is produced from the shrub Aspalathus linearis and is a popular native herbal tisane. It is popular because it is marketed as caffeine free and very low in tannins and so an alternative to coffee and camellia based teas. The tea is made from both leaves and stems of the bush and is available in its unfermented, semi-fermented and fermented formats, each of which has varying degrees of health benefits, palatability and quality.

Once consumed only in South Africa, most European countries and the USA have taken to it and it is steadily developing its global market. It is also a commercially important crop for South Africa as it is not easily cultivated elsewhere (Morton, 1983).

Description

The plant grows mainly in the Western Cape of South Africa but is assiduously cultivated in an around Cederberg.  The plant is described as an “erect to spreading, highly variable shrub or shrublet up to 2 m high.  Its young branches are usually red to brown. The leaves are green and needle-like, 15-60 mm long and up to about 1 mm thick. They are without stalks and stipules and may be densely clustered. The yellow flowers, which appear in spring to early summer, are solitary or arranged in dense groups at the tips of branches. The fruit is a small lance-shaped pod usually containing one or two hard seeds.”

Processing

Unfermented tea is simply prepared by collecting the leaves and stems, finely milling and packaging ‘as is’. In the fermentation process which is similar to that for other types of teas, the leaves and stems are fermented by oxidation in various degrees of heat and humidity. The oxidation process generates the red-brown colour hence the Red Bush epithet. A more exacting fermentation is required for producing green rooibos as with other green teas. In sensory terms, the traditional unfermented rooibos has a green, woody note which becomes more malt-like and grassy on fermentation.

Nutritional Content

Rooibos plant is rich in polyphenols and is still used traditionally for medicinal purposes. Many polyphenols, particularly the flavonoids, have been known to possess relatively potent antioxidant, anti-atherosclerotic, anti-inflammatory, antimutagenic, antitumor, and antiviral activity (Nijveldt et al., 2001) in the many plant studies they have been surveyed in. It is little wonder that the Red Bush Tea then attracted many to its benefits because it rich in these flavonoid compounds.

The flavonoids include aspalathin (ca. 50mg/g), isoorientin (3.4 mg/g), orientin (2.3 mg/g), nothofagin (Joubert, 1996), vitexin, quercetin, luteolin, (+)-catechin and rutin (1.7 mg/g) that contribute to the antioxidant and some of the antimicrobial activities. The phenolic acids identified include protocatechuic acid, caffeic acid, p-hydroxybenzoic acid, p-coumaric acid, ferulic acid, syringic acid, and vanillic acid (Rabe et al., 1994; von gadow et al., 1997).

The interest in the biochemical properties was first raised with an in-depth analysis of the antioxidant properties of its significant flavonoid, aspalathin, by a research group which has been very active with regards this plant, from the University of Stellenbosch in South Africa. Aspalathin is the major flavonoid in unfermented tea and was compared in an antioxidant study to standard functional ingredients such as α-tocopherol, BHT, and BHA and some of the polyphenols found in the tea (von Gadow et al., 1997). Here, the test methods were β-carotene bleaching, the α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging technique, and an automated Rancimat method. Aspalathin was not as effective as BHT or β-carotene where preventing lipid oxidation was concerned but it appeared to have better radical scavenging or mopping up activity in the DPPH assay.

In the pharmacologocal sense, there is interest as in all teas especially green tea, that it may minimise the impact of certain cancers (Ito et al., 1991; Komatsu et al., 1994; Yoshikawa et al., 1990). One key study by the same research team at Stellenbosch found that Rooibos tea was not as effective as green, oolong or black teas in the β-carotene bleaching method but was just behind green tea in all its various formats where the DPPH radical scavenging method was concerned. Generally, the unfermented tea compared to the fermented version is the more effective free-radical scavenger (Bramati et al., 2003) as was examined in the ABTS^•+ radical cation decolorization assay. Green and black teas were more effective though in free-radical scavenging. It also prompted a study to look at the various radical scavenging behaviour of the tea at different forms of processing. As is the case with conevntional tea processing, the unfermented or lightly processing forms have the highest antioxidant potentials (Standley et al., 2001).

There was a later study which warned of the issues associated with flavonoid-enriched fractions of rooibos because the polyphenols such as aspalathin and nothofagin had a pro-oxidant effect based on various free-radical assays applied (Joubert et al., 2005). Most recently, cell studies showed that rooibos was effective against high glucose mediated inflammation which hints at a diabetes treatment without stating it (Ku et al., 2015).

A number of claims made on various web-sites state have been made for the tea in all its formats. It improves blood circulation and acts as a gastrointestinal calmer. It produces a tea not only caffeine free but very low in tannins (Blommaert and Steenkamp, 1978).

The health aspects have been more effectively reviewed by McKay and Blumberg (2007).

The antimicrobial activities of rooibos on different bacterial species have been reported in various studies (Schepers, 2001; Negi et al., 2003; Taguri et al., 2004; Almajano et al., 2008).

Revised 16th April 2016.

References

Almajano, M.P., Carbo, R., Jiménez, J., Gordon, M.H. (2008) Antioxidant and antimicrobial activities of tea infusions. Food Chem. 108  pp.55–63

Blommaert, K.L.J., Steenkamp, J., (1978). Tannien-en moontlike kafeieninhoud van rooibostee, Aspalathus (subgen. Nortiera) linearis (Brum. Fil) R. Dahlgr. Agroplantae 10, pp. 49.

Bramati, L., Aquilano, F., & Pietta, P. (2003). Unfermented rooibos tea: quantitative characterization of flavonoids by HPLC-UV and determination of the total antioxidant activity. J. Agric. Food Chem., 51(25), pp. 7472-7474  doi:10.1021/jf025697h

Joubert, E. (1996). HPLC quantification of the dihydrochalcones, aspalathin and nothofagin in rooibos tea (Aspalathus linearis) as affected by processing. Food Chemistry 55 (4) pp. 403–411. doi:10.1016/0308-8146(95)00166-2

Joubert, E., Winterton, P., Britz, T. J., & Gelderblom, W. C. (2005). Antioxidant and pro-oxidant activities of aqueous extracts and crude polyphenolic fractions of rooibos (Aspalathus linearis). J. Agric. Food Chem., 53(26), pp. 10260-10267

Ku, S. K., Kwak, S., Kim, Y., Bae, J. S. (2015). Aspalathin and Nothofagin from Rooibos (Aspalathus linearis) inhibits high glucose-induced inflammation in vitro and in vivo. Inflammation 38 (1): pp. 445–55. doi:10.1007/s10753-014-0049-1. PMID 25338943

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

Morton, J. F. (1983). Rooibos tea, aspalathus linearis, a caffeineless, low-tannin beverage. Economic Botany 37 (2): 164–73. doi:10.1007/BF02858780. JSTOR 4254477

Nijveldt, R.J., van Nood, E., van Hoorn, D.E.C., Boelens, P.G., van Norren, K., van Leeuwen, P.A.M. (2001) Flavonoids: a review of probable mechanisms of action and potential applications. Am. J. Clin. Nutr. 74   pp. 418–25

Rabe, C., Steenkamp, J.A., Joubert, E. Burger, J.F., Ferreira, D. (1994) Phenolic metabolites from rooibos tea (Aspalathus linearis). Phytochemistry 35 pp. 1559–1565. doi:10.1016/S0031-9422(00)86894-6

Schepers S. (2001) Anti-microbial activity of rooibos tea (Aspalathus Iinearis) on food spoilage organisms and potential pathogen. [MSc thesis]. Stellenbosch, South Africa.: Stellenbosch Univ. 121 p. Available from: Stellenbosch Univ.–SUN Scholar Research Repository, Matieland,

Standley, L., Winterton, P., Marnewick, J.L., Gelderblom, W.C., Joubert, E., Britz, T.J. (January 2001). Influence of processing stages on antimutagenic and antioxidant potentials of rooibos tea.”. Journal of Agricultural and Food Chemistry 49 (1): 114–7 doi:10.1021/jf000802d. PMID 11170567

Stellenbosch; http://scholar.sun.ac.za/handle/10019.1/18345. Accessed 2012 October 15.

Taguri, T., Tanaka, T., Kouno, I. (2004) Antimicrobial activity of 10 different plant polyphenols against bacteria causing food-borne disease. Biol. Pharm. Bull. 27  pp. 1965–69

von Gadow, A., Joubert, E., & Hansmann, C. F. (1997). Comparison of the antioxidant activity of aspalathin with that of other plant phenols of rooibos tea (Aspalathus linearis), α-tocopherol, BHT, and BHA. J. Agric. Food Chem., 45(3), pp. 632-638.

______________________________________ (1997). Comparison of the antioxidant activity of rooibos tea (Aspalathus linearis) with green, oolong and black tea. Food Chem., 60(1), pp. 73-77. doi:10.1016/S0308-8146(96)00312-3