Summaries of selected Rooibos health research articles published 2005 – 2010
Chrysoeriol, an antioxidant present at low levels in Rooibos, can prevent and treat vascular disease in
humans. Chrysoeriol is able to inhibit the migration of smooth muscle cells inside the aorta, a key cause of
atherosclerosis (narrowing or hardening of the arteries). The research was done on human aorta cells.
Scientists therefore recommend the use of chrysoeriol to prevent and treat the repeated narrowing of
blood vessels following coronary angioplasty. During angioplasty, a small balloon is used to open up a
blocked or narrowed heart artery. Note: Often only trace quantities of chrysoeriol are found in Rooibos.
Cha, B., Shi, W.L., Yonezawa, T., Teruya, T., Nagai, K., Woo, J., 2009. An inhibitory effect of chrysoeriol on
platelet-derived growth factor (PDGF)-induced proliferation and PDGFreceptor signaling in human aortic
smooth muscle cells. Journal of Pharmacological Science 110, 105–110.
Swedish researchers found that Rooibos could help to promote heart health in humans. They found that
30 and 60 minutes after drinking 400 ml of Rooibos, the activity of a specific enzyme (called angiotensinconverting enzyme, or ACE) is significantly inhibited. This enzyme is believed to be involved in the
development of cardiovascular disease, and therefore ACE inhibitors are used to treat hypertension and
heart disease. The research team could not demonstrate the same effect with green tea and black tea in
the group of 17 healthy volunteers who participated in the study. Persson, I.A., Persson, K., Hägg, S.,
Andersson, R.G.G., 2010. Effects of green tea, black tea and Rooibos tea on angiotensin-converting enzyme
and nitric oxide in healthy volunteers. Public Health Nutrition 3(5), 730–737.
A South African study in humans showed that taking six cups of Rooibos every day for a period of six
weeks significantly reduced several of the pertinent biomarkers associated with cardiovascular disease
and protects the body against oxidative damage of blood lipids. The liver and kidney functions of the 40
participants were monitored and no adverse effects from taking six cups of rooibos per day were found.
Marnewick, J.L., 2010. Rooibos and honeybush: Recent advances in chemistry, biological activity and
pharmacognosy. In: African natural plant products: New discoveries and challenges in chemistry and quality.
Juliani, H.R., Simon, J.E., Ho, C.T. (Eds). ACS Symposium Series Volume 1021, American Chemical Society,
Washington DC, USA, pp 277–294.
A study in the Slovak Republic found that Rooibos provides effective protection against oxidative stress in
diabetic rats. These scientists recommend the use of Rooibos for the prevention and therapy of diabetic
vascular complications, especially to protect ocular (eye) membrane systems against peroxidation. Uličná,
O., Vančová, O., Božek, P., Čársky, J., Šebeková, K., Boor, P., Nakano, M., Greksák, M., 2006. Rooibos tea
(Aspalathus linearis) partially prevents oxidative stress in streptozotocin-induced diabetic rats. Physiology
Research 55, 157–164.
Two South African researchers, Professor Elizabeth Joubert and Dr Johan Louw, are co-applicants of a
worldwide patent (filed in 2007) to develop and produce an anti-diabetic extract of Rooibos, particularly
Summaries of selected Rooibos health research articles published 2005 – 2010, Published May 2010
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for the treatment of type 2 diabetes. Their invention will provide new uses for aspalathin and rutin in the
prevention and treatment of this disease.
A 2009 study in Japan found that aspalathin helped to improve the glucose uptake of muscle cells (and
thereby helped to maintain normal blood sugar levels) in mice with type 2 diabetes. Aspalathin also
stimulates pancreatic beta-cells to secrete insulin and helps to improve impaired glucose tolerance in
these animals. Kawano, M., Nakamura, H., Hata, S., Minakawa, M., Miura, Y., Yagasaki, K., 2009.
Hypoglycemic effect of aspalathin, a rooibos tea component from Aspalathus linearis, in type 2 diabetic
model db/db mice. Phytomedicine 16, 437–443.
A German research group found that aspalathin is metabolised in pig intestine and that aspalathin
metabolites were present in their urine (pigs are considered a good model for humans). Kreuz, S., Joubert,
E., Waldman, K., Ternes, W., 2008. Aspalathin, a flavonoid in Aspalathus linearus (rooibos), is absorbed by
pig intestine as a C-glycoside. Nutrition Research 28, 690–701.
The metabolism of aspalathin was confirmed in humans in a collaborative study by researchers in the UK
and Switzerland. They found metabolites of aspalathin in the urine of the study participants. Courts, F.L. &
Williamson, G., 2009. The C-glycosyl flavonoid, aspalathin, is absorbed, methylated and glucuronidated
intact in humans. Molecular Nutrition & Food Research, 53(9), 1104–1111.
Unpublished research from Germany found unmetabolised aspalathin in the blood of human study
participants when they consumed green Rooibos. Poster paper presented at 38th German Food Chemists
Day, 14–16 September 2009, Berlin, Germany.
A study in Italy found flavonoid metabolites in the urine of ten human volunteers after they had drunk 500
ml green and fermented Rooibos. Most metabolites were excreted within five hours of tea consumption.
Stalmach, A., Mullen, W., Pecorari, M., Serafini, M., Crozier, A., 2010. Bioavailability of C-linked
dihydrochalcone and flavanone glucosides in humans following ingestion of unfermented and fermented
rooibos teas. Journal of Agricultural and Food Chemistry, 57 (15), 7104–7111.
Joint research between the Agricultural Research Council and the Medical Research Council were able to
show that two Rooibos antioxidants – aspalathin and nothofagin – are changed by the liver enzymes in
vitro. Van der Merwe, J.D., Joubert, E., Manley, M., De Beer, D., Malherbe, C., Gelderblom, W.C.A., 2010. In
vitro hepatic biotransformation of aspalathin and nothofagin, dihydrochalcones of rooibos (Aspalathus
linearis), and assessment of metabolite antioxidant activity. Journal of Agricultural and Food Chemistry 58,
Japanese researchers have been investigating the estrogenic activity of Rooibos compounds (in vitro) and
were able to show that three of these compounds had potential estrogenic activity. Such plant-derived
estrogens are of interest because of their potential as an alternative to the estrogens in hormone
replacement therapy. Shimamura, N., Miyase, T., Umehara, K., Warashina, T., Fujii, S., 2006. Phytoestrogens
from Aspalathus linearis. Biology and Pharmacology Bulletin 29, 1271–1274.
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The ability of South African herbal teas (Rooibos and Honeybush extracts) to act as “chemopreventors” in
skin cancer was highlighted by a South African research team using an animal model. They showed that
topical (external) application of tea fractions significantly suppressed tumour growth in mice with skin
cancer, when using processed and unprocessed tea. Marnewick, J.L., Joubert, E., Joseph, S., Swanevelder,
S., Swart, P., Gelderblom, W.C.A., 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, 193–202.
South African researchers collaborated to compare the potential of different kinds of tea (Rooibos,
Honeybush, black oolong and green tea) to suppress mutations, and thereby prevent cancer. Their results
confirmed that the phenolic compounds in herbal tea extracts have a strong anti-mutagenic effect (in vitro
study using cell lines). Van der Merwe, J.D., Joubert, E., Richards, E.S., Manley, M., Snijman, P.W.,
Marnewick, J.L., Gelderblom, W.C.A., 2006. A comparative study on the antimutagenic properties of aqueous
extracts of Aspalathus linearis (rooibos), different Cyclopia spp. (honeybush) and Camellia sinensis teas.
Mutation Research 611, 42–53.
Acknowledging that Rooibos is widely used to treat gastrointestinal upsets, researchers in Pakistan,
Canada and Germany joined forces to explore the mechanism of this effect of Rooibos. They used rabbit
jejunum (intestine) tissue for this study. Their results explain the biochemistry of how the flavonoids and
other active ingredients in Rooibos achieve this calming effect on the digestive system. They concluded
that it is justified to use Rooibos for the treatment of gastrointestinal disorders, such as gut spasms. Gilani,
A.H., Khan, A., Ghayur, M.N., Ali, S.F., Herzig, J.W., 2006. Antispasmodic effect of rooibos tea (Aspalathus
linearis) is mediated through K+ channel activation. Basic Clinical Pharmacology and Toxicology 99, 365–373.
A Japanese study showed that Rooibos could reduce inflammation in rats with colitis (open sores in the
colon) via increased antioxidant activity with a consequent reduction in damage to DNA caused by
oxidation. These researchers recommend Rooibos as a safe and useful way to reduce oxidative stress.
Baba, H., Ohtsuka, Y., Haruna, H., Lee, T., Nagata, S., Maeda, M. Yamashiro, Y., Shimizu, T., 2009. Studies of
anti-inflammatory effects of Rooibos tea in rats. Pediatrics International 51, 700–704.
Researchers in Pakistan found that chrysoeriol (a bioactive components of Rooibos, but usually only
present at low levels) acted effectively as a bronchodilator, with an associated effect on lowering blood
pressure and relieving spasms. Aorta, trachea and other tissue from rabbits and guinea-pigs were used to
illustrate this effect. Chrysoeriol is known for its antioxidant, anti-inflammatory, antitumor, antimicrobial,
antiviral and free radical scavenging abilities. Khan, A., Gilani, A.H., 2006. Selective broncholdilatory effect
of rooibos tea (Aspalathus linearis) and its flavonoid, chrysoeriol. European Journal of Nutrition 45, 463–469.
Summaries of selected Rooibos health research articles published 2005 – 2010, Published May 2010
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Research teams in Japan demonstrated that the active ingredients in a water-soluble fraction of Rooibos
restored immune function in immune-suppressed rats. These results hold significant potential for future
research into the immune-boosting properties of Rooibos that could potentially benefit people living with
HIV/AIDS. Ichiyama, K., Tai, A., Yamamoto, I., 2007. Augmentation of antigen-specific antibody production
and IL-120 generation with a fraction from rooibos (Aspalathus linearis) tea. Bioscience, Biotechnology and
Biochemistry 71, 589–602.
Researchers from the Slovak Republic were able to demonstrate the anti-ageing effect of Rooibos in
Japanese quails. The birds were given Rooibos to drink and had ground Rooibos added to their food. The
hens on the Rooibos diet laid more eggs and kept on laying eggs as they were getting older, compared to
quail hens on a standard diet. Juráni, M., Lamošová, D., Máčajová, M., Kostál, L., Joubert, E., Greksák, M.,
2008. Effect of rooibos tea (Aspalathus linearis) on Japanese quail growth, egg production and plasma
metabolites. British Poultry Science 49, 55–64.
The research reviews listed below provide a comprehensive overview of recent research into the potential
health benefits, production and quality aspects of Rooibos and related products.
1. Joubert, E. & Schulz, H., 2006. Production and quality aspects of rooibos tea and related products. A
review. Journal of Applied Botany and Food Quality 80, 138–144.
2. 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, 1–16.
3. Joubert, E., Gelderblom, W.C.A., Louw, A., De Beer, D., 2008. South African herbal teas: Aspalathus
linearis, Cyclopia spp. and Athrixia phylicoides – A review. Journal of Ethnopharmacology, 119,
4. Joubert, E., Gelderblom, W.C.A., Louw, A., De Beer, D., 2008. Phenolic contribution of South African
herbal teas to a healthy diet. Natural Product Communications 4, 1–18.
Research abstracts are available online at one or more of the following links:
Rooibos research summaries are updated on the SA Rooibos Council web site:
Published May 2010
Summaries of selected Rooibos health research articles published 2005 – 2010, Published May 2010
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