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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 2, March/April 2020
AFRICA
81
Rooibos (
Aspalathus linearis
) protects against nicotine-
induced vascular injury and oxidative stress in Wistar rats
Michelle Smit-van Schalkwyk, Shantal Windvogel, Hans Strijdom
Abstract
Background:
Rooibos (
Aspalathus linearis
) is an indigenous
South African plant, traditionally used by the local popula-
tion as a remedy against several ailments. More recently,
rooibos was shown to exhibit potent antioxidant properties,
attributed to its polyphenols. We assessed whether treat-
ment with fermented rooibos (RF), unfermented rooibos
(RUF) and melatonin (Mel), a well-documented antioxidant
included for comparison, could counter the harmful vascular
and pro-oxidant effects of nicotine.
Methods:
Vascular function, antioxidant enzyme activity and
lipid peroxidation were assessed in male adult rats treated with
nicotine (5 mg/kg body weight/day) and 2% RF, 2% RUF or
4% Mel co-administration. Nitric oxide (NO) production and
cell viability were measured in nicotine-exposed rat aortic
endothelial cells (AECs) pre-treated with RF (0.015 mg/ml).
Results:
Vascular studies showed that co-administration
with RF or Mel exerted anti-contractile and pro-relaxation
responses in aortic rings, and increased hepatic superoxide
dismutase and catalase activity in nicotine-exposed animals.
Co-treatment with Mel additionally decreased lipid peroxida-
tion in nicotine-exposed rats. RUF exerted anti-contractile
responses in aortic rings of nicotine-treated animals, while in
nicotine-exposed AECs, RF pre-treatment increased intracel-
lular NO levels.
Conclusion:
For the first time, we have shown that rooibos
co-treatment exerted beneficial vascular effects in nicotine-
exposed rats, and that this was associated with increased anti-
oxidant enzyme activity.
Keywords:
nicotine,
Aspalathus linearis
, rooibos, melatonin,
endothelial dysfunction
Submitted 4/12/18, accepted 3/9/19
Published online
Cardiovasc J Afr
2020;
31
: 81–90
www.cvja.co.zaDOI: 10.5830/CVJA-2019-052
Tobacco smoking is one of the most important risk factors for
the development of cardiovascular disease and is responsible
for approximately 12% (6.2 million) of all deaths globally.
1
It is
estimated that over five million people are current or ex tobacco
users and that over 600 000 non-smokers die from exposure
to second-hand smoke.
2
Nicotine, the addictive substance in
tobacco, is associated with the development of endothelial
dysfunction (ED) through oxidative stress. ED is an early,
reversible precursor of atherosclerosis.
3
In turn, atherosclerosis is
the underlying pathology for many cardiovascular diseases, often
resulting in myocardial infarction and stroke.
4
Nitric oxide (NO) plays an important role in protection
against the onset and progression of cardiovascular disease.
The ability of the endothelium to synthesise and release NO is
essential in regulating haemostasis, vessel tone, blood pressure
and vascular remodelling.
5
Furthermore, reactive oxygen species
(ROS) and the resultant oxidative stress are important mediators
of the pathological manifestations of ED. ROS reduce or
eliminate the protective abilities of NO, which in turn could lead
to ED.
6
Experimental and clinical data indicate that exposure to
nicotine increases oxidative stress and has the potential to
induce ED.
7
While endogenous mechanisms such as antioxidant
enzymes as well as non-enzymatic defences exist to combat
the deleterious effects of oxidative stress, they might not offer
sufficient protection against the ROS produced during nicotine
exposure.
8,9
Early endothelial changes such as ED are reversible,
10
rendering it clinically relevant to identify possible treatment
modalities such as anti-oxidant therapy, which could counter
the harmful effects of increased ROS production, and hence
restore the release of endothelioprotective NO. Protecting the
endothelium will result in reduced or delayed atherogenesis,
which lowers the risk of cardiovascular mortality. Such therapies
may include dietary supplementation with natural plant products
or chemically synthesised versions of endogenous molecules with
known antioxidant capacity.
Rooibos (
Aspalathus linearis
) is an indigenous South African
plant that is popularly consumed as a beverage and is known
to possess bio-active properties.
11
Rooibos boasts a unique
flavonoid content and contains various dihydrochalcones,
including aspalathin, a C-linked dihydrochalcone glucoside,
12,13
and aspalanin, a cyclic dihydrochalcone,
14
which are both unique
to
Aspalathus linearis
.
Both unfermented (green) and fermented (red) forms of
rooibos are commercially available. Green rooibos is immediately
dried after the cutting phase, whereas non-enzymatic oxidative
degradation of aspalathin results in the characteristic red-brown
fermented form.
15
Rooibos has been shown to exert potent anti-
oxidant, immune-modulating and chemo-protective actions,
with the additional benefit of having minimal adverse effects.
16
In addition, rooibos possesses cardioprotective properties,
including the improvement of dyslipidaemia and redox status
in human study participants,
17
as well as being able to exert
protective effects on cultured cardiomyocytes from diabetic rats.
18
Centre for Cardio-metabolic Research in Africa, Division
of Medical Physiology, Biomedical Sciences, Faculty of
Medicine and Health Sciences, Stellenbosch University,
Tygerberg, South Africa
Michelle Smit-van Schalkwyk, PhD, michelle.smitvanschalkwyk@
gmail.comShantal Windvogel, PhD
Hans Strijdom, PhD