Troncales

Rooibos has numerous reputed health benefits that contribute to its popularity (Joubert & de Beer, 2011:869). Rooibos has been recommended for the following health conditions: allergies (asthma and hay fever), skin problems (eczema and acne), digestive disorder and stomach problems due to its antispasmodic properties, nervous conditions and age-related problems (Tiedtke & Marks, 2002:16). The unique phenolic metabolites of rooibos herbal tea, which among others, act as potent antioxidants, may be the link to its health promoting effects. Research has indicated antimutagenic, anticarcinogenic, anti-inflammatory and antiviral activities in rooibos herbal tea infusions (Joubert & Ferreira, 1996:82). Table 2.2 provides a summary of the experimental and human research studies that investigated the health promoting properties of rooibos.

Table 2.2: Summary of reported research on the health promoting effects of rooibos herbal tea

Bioactivity Form(s) of rooibos Objective(s) of study in

relation to consumption

Outcome(s) on consumption

Reference Cardiacprotection Aqueous extract

UR1 _{and FR}2

Effect of rooibos supplementation on ischaemia / reperfusion injury in the isolated perfused rat heart

Decreased pro-apoptotic proteins; Improved aortic output recovery Pantsi et al., 2011:1220- 1228 FR consumed as beverage Effect of rooibos on biochemical and oxidative stress parameters in adults at risk for CVD3

Increased plasma total polyphenol content; Decreased lipid peroxidation, serum LDL4_- cholesterol and triacylglycerols; Increased HDL5_-cholesterol Marnewick et al., 2011:46-52 Aqueous extract rooibos herbal tea

Effects of green, black and rooibos herbal tea on ACE6 _{and NO}7 _{of healthy}

volunteers

Inhibited ACE activity; No significant effect on NO concentration Persson et al., 2010:730-737 Oxidative stress reduction Aqueous extract UR and FR Antioxidant status as reflected by redox state of glutathione and the ORAC8 _{in the liver of rats}

exposed to the various tea preparations and modulation of drug metabolising enzymes in the liver of rats by rooibos and honeybush

UR increased the activity of the microsomal UDP- glucoronosyl transferase; Reduced oxidised glutathione levels; Increased reduced glutathione Marnewick et al., 2003:8113- 8119 Ready-to-drink UR and FR formulated with rooibos extract powder

Effect of rooibos on TAC9_{, lipid}

triacylglycerols, cholesterol and

glycaemia plasma levels in humans

Increased plasma antioxidant capacity; No changes in triacylglycerols, cholesterol and glycaemia plasma levels

Villano et al., 2010:679-683

Chemoprotection Aqueous extract UR and FR

Modulating properties of herbal teas, black and green tea against oxidative parameters and cancer promoting activity induced by FB1 in rat liver

FR decreased lipid peri- oxidation; UR decreased number of foci Marnewick et al., 2009:220- 229 Aqueous extract UR and FR

Effects of rooibos and honeybush herbal teas on the development of esophageal papillomas in Fischer rats

UR reduced mean total papilloma size

Sissing et al., 2011:600-610

Anti-inflammatory effect

Aqueous extract UR Effects of rooibos herbal tea on prevention of inflammation and dextran sodium sulphate induced rat colitis

Increased SOD10 _levels;

Decreased 8-hydroxy- 2’deoxyguanosine

Baba et al., 2009:700-704

1 _{UR: Unfermented rooibos} 2 _{FR: Fermented rooibos} 3 _{CVD: Cardiovascular disease} 4 _{LDL: Low-density lipoprotein} 5 _{HDL: High-density lipoprotein} 6 _{ACE: Angiotensin-converting enzyme} 7 _{NO: Nitric oxide}

8 _{ORAC: Oxygen radical absorbance capacity} 9 _{TAC: Total antioxidant capacity}

In relation to its cardioprotective effects, Marnewick et al. (2011:46) investigated the effect of regular rooibos herbal tea consumption on oxidative stress and biochemical indicators in subjects at risk for CVD. The study was the first to report the influence rooibos has on oxidative stress and the lipid profile of adults at risk for the onset of CVD, which were found to be improved on the daily consumption of six cups (1 200 mL) per day for six weeks (Marnewick et

al., 2011:50). Villano et al. (2010:682) and Nikolova et al. (2007:120) also confirmed the lipid

profile modulation and oxidative stress reduction properties of unfermented and fermented rooibos herbal teas in healthy humans and that these rooibos herbal teas boost plasma antioxidant capacity. Pantsi et al. (2011:1224) also reported on the cardioprotective properties of rooibos. In this study male Wistar rats consumed fermented and unfermented rooibos for seven weeks whereafter the rat hearts were exercised and placed on working cardio perfusion equipment. The rats that received the fermented rooibos (67.7 ± 8.12 mg daily) ingested significantly (p < 0.05) lower total polyphenols in comparison to those that received unfermented rooibos (74.62 ± 3.41 mg daily) and green tea (95.58 ± 7.16 mg daily). The flavonol intake of those that received green tea (3.81 ± 0.56 mg daily) was significantly (p < 0.05) lower in comparison to that of the rats that received the unfermented (13.61 ± 1.07 mg daily) and fermented (20.65 ± 3.41 mg daily) rooibos (Pantsi et al., 2011:1222). The rats receiving the unfermented and fermented rooibos indicated an improved aortic output recovery due to the higher intake of flavonols (Pantsi et al., 2011:1225).

Marnewick et al. (2009:220) investigated the chemoprotective attributes of fermented and unfermented honeybush and rooibos herbal teas and black and green teas against FB1 elevation in rat liver utilising diethylnitrosamine (DEN) as cancer originator. The protective effects of the herbal teas under study were decreased by the fermentation process as the unfermented honeybush and rooibos significantly (p < 0.05) to marginally (p < 0.1) decreased the total amount of foci respectively, while the relative amount of larger foci was reduced with all the teas studied (Marnewick et al., 2009:220). The effect that flavonoids have in chemoprotection is possibly as a result of their inflection on the action of the carcinogen in the cell. A flavonoid cell interaction affects the cell’s level of xenobiotic metabolising enzymes and its oxidative profile, which inhibits and / or reduces the binding of reactive carcinogenic metabolites to the cell macromolecules, such as the protein and DNA (Joubert et al., 2008:401). The two rooibos flavonoids, quercetin and luteolin are furthermore known to initiate death of cancer cells (Rubin, 2010:48).

Baba et al. (2009:700) used an experimental rat study to investigate the anti-inflammatory properties of rooibos. Seven-week-old Wistar rats were grouped with one group receiving rooibos herbal tea and the other group water. The 8-hydroxy-2’-deoxyguanosine levels in the urine decreased significantly (p < 0.05) while the SOD levels in the serum increased significantly (p < 0.05) in the group consuming rooibos in comparison to the control group which received water. The findings from the study indicated that rooibos herbal tea may prevent inflammation and damage to DNA in vivo due to its antioxidant activity (Baba et al., 2009:700).