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'African Potato' (Hypoxis hemerocallidea corm): A Plant-Medicine for Modern and 21st Century Diseases of Mankind? - A Review

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Abstract

The traditional uses, therapeutic attributes, phytochemical and pharmacological profiles of 'African potato' (Hypoxis hemerocallidea corm) extracts have been reviewed. Available biomedical evidence suggests that 'African potato' is a potential plant-medicine for some modern and 21st century diseases of mankind. Thus far, biomedical evidence has revealed that 'African potato' extracts possess antiinflammatory, antineoplastic, antioxidant, antidiabetic and antiinfective properties in vivo and in vitro. However, more laboratory and clinical studies are required to clarify these observations, and to isolate, purify and characterize the active chemical constituents responsible for the herb's pharmaco-therapeutic effects.
‘AFRICAN POTATO’: A PLANT-MEDICINE FOR MODERN DISEASES? 147
Copyright © 2008 John Wiley & Sons, Ltd. Phytother. Res. 23, 147–152 (2009)
DOI: 10.1002/ptr
Copyright © 2008 John Wiley & Sons, Ltd.
PHYTOTHERAPY RESEARCH
Phytother. Res. 23, 147–152 (2009)
Published online 11 August 2008 in Wiley InterScience
(www.interscience.wiley.com) DOI: 10.1002/ptr.2595
Received 6 February 2008
Revised 28 April 2008
Accepted 9 May 2008
* Correspondence to: John A. O. Ojewole, Department of Pharmacology,
School of Pharmacy and Pharmacology, Faculty of Health Sciences, Univer-
sity of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa.
E-mail: Ojewolej@ukzn.ac.za
REVIEW ARTICLE
‘African Potato’ (Hypoxis hemerocallidea
corm): A Plant-Medicine for Modern and 21st
Century Diseases of Mankind? – A Review
Peter M. O. Owira and John A. O. Ojewole*
Department of Pharmacology, School of Pharmacy and Pharmacology, Faculty of Health Sciences, University of KwaZulu-Natal,
Private Bag X54001, Durban 4000, South Africa
The traditional uses, therapeutic attributes, phytochemical and pharmacological profiles of ‘African potato’
(Hypoxis hemerocallidea corm) extracts have been reviewed. Available biomedical evidence suggests that
‘African potato’ is a potential plant-medicine for some modern and 21st century diseases of mankind. Thus far,
biomedical evidence has revealed that ‘African potato’ extracts possess antiinflammatory, antineoplastic, anti-
oxidant, antidiabetic and antiinfective properties in vivo and in vitro. However, more laboratory and clinical
studies are required to clarify these observations, and to isolate, purify and characterize the active chemical
constituents responsible for the herb’s pharmaco-therapeutic effects. Copyright © 2008 John Wiley & Sons, Ltd.
Keywords: traditional herbal medicines; ‘African potato’ extracts; plant-medicine; pharmaco-chemical profiles; therapeutic
attributes.
INTRODUCTION
African Traditional Medicines and ‘African Potato’
It has been estimated that about 80% of the general
population in sub-Saharan Africa use African traditional
medicines (Hostetmann et al., 2000; Puckree et al., 2002)
and that as many as 100 000 traditional healers are in
practice in South Africa alone, with a contingent of
herbal trade industry worth approximately R500 million
per annum (Mander, 1998). It has also been estimated
that the ratio of traditional healers and orthodox medi-
cal doctors to the population in South Africa is 1:500
and 1:40 000, respectively (Abdool-Karim et al., 1994).
Traditional medicine, therefore, plays a critical role in
the healthcare delivery system of South Africa, given
the poor state of healthcare infrastructure, increased
disease burden occasioned by the HIV/AIDS pandemic,
and other chronic ailments that Western medicines
have failed to cure. The importance of herbal medi-
cines (phytomedicines) in this regard is only now being
appropriately recognized. The Ministries of Health of
several African countries have recently formulated
policies that promote the use of African traditional
medicines for the management, control and treatment
of HIV/AIDS-related diseases and other chronic ail-
ments of man (Morris, 2002; Southern Africa Develop-
ment Community, 2002).
The recent renewed interest in African traditional
medicines has attracted the attention of not only
government and private research laboratories and insti-
tutes, but also of pharmaceutical industries, in order
to rationalize the scientific and therapeutic values of
African traditional medicines. One African medicinal
plant that has enjoyed long usage as a traditional herbal
medicine in southern Africa is Hypoxis hemerocallidea
(also known as H. rooperi). This popular ‘miracle’
medicinal plant is widely distributed in the southern
Africa sub-region. The plant is characterized by strap-
like leaves, and bright yellow, star-shaped flowers (Van
Wyk et al., 2002). The tuberous rootstock (i.e. the corm)
of the plant is commonly referred to as ‘African potato’,
because of its potato-like shape. Traditionally, after
washing with clean water, the plant’s corms are chopped
into small pieces, boiled for about 20 min, and then the
decoction is consumed orally. This oral administration
is estimated to correspond to a daily dose of 250 mL,
derived from about 20 g of the corms (Nair et al., 2007a;
Pujol, 1990). ‘African potato’ extracts, powders, infu-
sions and decoctions have been used for centuries by
southern African traditional healers for the treatment,
management and/or control of an array of human ailments,
including cancers, nervous disorders, immune-related
illnesses, heart weaknesses and urinary tract infections
(Singh, 1999). Indeed, among the Swazis of Swaziland,
Hypoxis hemerocallidea is often referred to in siSwati
as ‘zifozonke’, meaning: ‘the plant that can be used to
treat many diseases’ (Amusan et al., 2007). Some of the
outstanding critical questions that still require answers
about ‘African potato’ include: (i) what has made
‘African potato’ so unique in the family of ‘African
herbal medicines’, and (ii) why has it taken researchers
and healthcare providers so long a time to exploit
and maximize the potential therapeutic benefits of this
‘wonder’ plant-medicine?
Copyright © 2008 John Wiley & Sons, Ltd. Phytother. Res. 23, 147–152 (2009)
DOI: 10.1002/ptr
148 P. M. O. OWIRA AND J. A. O. OJEWOLE
BIOLOGICAL ACTIVITY
Therapeutic and pharmacological considerations
In recent years, attempts have been made to investigate
the scientific basis of the therapeutic claims attributed
to ‘African potato’. Evidence-based laboratory investi-
gations indicate that aqueous and alcohol extracts of
‘African potato’ possess many interesting pharmaco-
logical properties, including antinociceptive (in mice),
antiinflammatory and antidiabetic properties (in rats)
in vivo (Ojewole, 2006). ‘Intraperitoneal injections of
50800 mg/kg body weight of “African potato” extracts
produced significant and dose-dependent anti-nociceptive
effects against chemically- and thermally-induced noci-
ceptive pain in mice’ (Ojewole, 2006). At the same dose
level, oral administrations of H. hemerocallidea corm
extracts also ‘significantly inhibited egg albumin-induced
acute inflammation, and reduced blood glucose levels
in both normal and streptozotocin-induced diabetic rats
in a dose-dependent manner’ (Ojewole, 2006). These
observations, therefore, suggest that extracts of ‘African
potato’ could possess antiinflammatory and antidiabetic
(hypoglycaemic) properties, respectively. As suggested
by Ojewole (2006), the extracts of ‘African potato’ could
inhibit the synthesis, production and/or release of in-
flammatory cytokines and mediators such as prostaglandins.
Recent reports have indicated that lectin-like proteins
purified from aqueous extracts of ‘African potato’ can
inhibit cyclooxygenase (COX) enzyme that mediates
prostaglandin synthesis in vitro (Gaidamashivili and
Van Staden, 2006). However, other studies have shown
that ethanol extracts of H. hemerocallidea have higher
inhibitory effects on COX-1 catalysed prostaglandin
synthesis than aqueous extracts of the plant’s corms
(Steenkamp et al., 2006). Aqueous extracts of H.
hemerocallidea corms have previously been shown
to scavenge free radicals (hydroxyl ions) in vitro
(Mahomed and Ojewole, 2003), and it has been sug-
gested that the ability of the corm’s extracts (both
aqueous and ethanol) to suppress inflammation could
be mediated via its antioxidant activity which, in turn,
inhibits COX enzymes (Feng et al., 1995; Kumagai
et al., 2000; Mahomed and Ojewole, 2003; Steenkamp
et al., 2006). Taken together, these observations appear
to suggest that the reported antiinflammatory activity
of ‘African potato’ extracts could be due to their ability
to inhibit the synthesis of prostaglandins and other in-
flammatory mediators (see Fig. 1).
It has been reported that lectin-like proteins derived
from extracts of ‘African potato’ inhibited the growth
of Staphylococcus aureus, in vitro (Gaidamashivili and
Van Staden, 2002). Undoubtedly, agglutinins, found
in the storage parts (corms) of H. hemerocallidea, play
a critical role in the plant’s defensive mechanism against
pathogenic micro-organisms. This observation would,
therefore, support the age-old usage of ‘African potato’
in the treatment of microbial infective disorders (Hutchings
et al., 1996; Van Wyk et al., 2002). Laboratory reports
have further shown that both ethanol and aqueous
extracts of H. hemerocallidea corm inhibit the growth
of Escherichia coli, in vitro (Steenkamp et al., 2006),
an observation quite consistent with the previously
Figure 1. A summary of the putative pharmacological actions of ‘African potato’ extracts (rooperol and stigmasterol) on some cellular
pathways so far investigated. Antiinflammatory activity of ‘African potato’ extracts could be attributed to inhibition of lipoxygenase,
cyclooxygenase (COX) and cytokines production. Antioxidant activity of the extracts could be mediated via reduced reactive oxygen
species (ROS) production, either from diminished activity or expression of drug metabolizing enzymes, or from direct inhibition of
COX. Increased expression of pregnane X receptor (PXR) binds xenobiotics and triggers over-expression of P-glycoproteins and
some drug metabolizing enzymes, thus causing toxicity related to drug resistance or herbal drug reactions. Effects of ‘African potato’
extracts on organic cation transporters (OCT) are not known. = inhibitory effects of ‘African potato’ extracts; = xenobiotics; =
up-regulation/stimulation; = down-regulation/inhibition.
‘AFRICAN POTATO’: A PLANT-MEDICINE FOR MODERN DISEASES? 149
Copyright © 2008 John Wiley & Sons, Ltd. Phytother. Res. 23, 147–152 (2009)
DOI: 10.1002/ptr
reported antibacterial activity of ‘African potato’
(Gaidamashivili and Van Staden, 2002). Escherichia coli
infection is the most common secondary cause of bac-
terial prostatitis (Steenkamp et al., 2006). This observa-
tion may, therefore, partly also explain the traditional
usage of the extracts of this plant’s corm in the treat-
ment of urinary tract infections (Singh, 1999).
Benign prostate hyperplasia (BPH) can cause blockade
of the urinary tract in men, and this may lead to chronic
bacterial prostatitis. Anecdotal and folkloric reports
have documented that ‘African potato’ extracts have
been used traditionally in the treatment of prostate
hyperplasia (Singh, 1999). The observation that ‘African
potato’ extracts can inhibit the growth of E. coli in vitro,
therefore, seems to support the use of this plant’s corm
in the treatment of prostate hyperplasia. Furthermore,
therapeutically useful steroids are present in Prunus
africanum and H. hemerocallidea. However, more recent
experimental and clinical evidence have suggested that
the effects of H. hemerocallidea corm extracts on BPH
might not only be due to their antibacterial activities,
but could also be due to their antiinflammatory and
antioxidant properties (Ojewole, 2002; Steenkamp
et al., 2006; Nair et al., 2007b). This body of evidence,
therefore, supports the claims that ‘African potato’
extracts may contain chemical compounds that suppress
tumour growth, and hence, its use in the treatment of
cancers.
It has recently been shown that aqueous extracts of
‘African potato’ caused bradycardia and brief hypoten-
sion in guinea-pigs and rats in vitro and in vivo, respec-
tively (Ojewole et al., 2006). Although the investigators
were unable to establish the precise pharmacological
mechanisms underlying their observations, they ruled
out involvement of the cholinergic system, since the
cardio-depressant effects of the extracts were not modi-
fied by atropine pretreatment (Ojewole et al., 2006).
However, in an earlier study using Chacma baboons,
Coetzee et al. (1996) reported that a purified extract of
H. hemerocallidea corm (rooperol) increased myocardial
contractility in vivo. Recently, a case study was pub-
lished where it was reported that chronic ingestion
of aqueous extract of ‘African potato’ (as tea) caused
ventricular tachycardia in a 25-year-old male subject
(Ker, 2005). The above conflicting cardiovascular ob-
servations tend to suggest that extracts of H. hemerocallidea
corm contain some bioactive chemical compounds with
cardiovascular activities. These findings may also lend
pharmacological credence to the age-old usage of this
plant in the treatment and/or management of heart
ailments and hypertension in some rural communities
of southern African.
However, what has recently stimulated the greatest
interest, not only among traditional healers and their
patients, but also in scientific communities, the phar-
maceutical industries, as well as in government circles,
is the claim that H. hemerocallidea corm can boost human
immune system. Some healthcare providers in South
Africa are currently using extracts of H. hemerocallidea
corms as immunostimulant preparations for patients
living with HIV/AIDS, on the strength of the recom-
mendation of South Africa’s national Department of
Health (Southern Africa Development Community,
2002; Mills et al., 2005a). In this regard, the use of this
plant’s corms has been extended to immune-related
illnesses, such as common cold, flu and arthritis (Mills
et al., 2005a). Unfortunately, despite the popular belief
in the immune-boosting properties of this plant’s corms,
there is absolutely no laboratory or clinical evidence
yet to support this immunostimulant claim, which at
present still remains speculative. Many clinical and labo-
ratory studies are, however, currently under way to
substantiate or refute the immunostimulant property
attributed to ‘African potato’ extracts.
PHYTOCHEMISTRY
Chemical constituents
Hypoxis hemerocallidea corm has a catalogue of anecdotal,
folkloric and therapeutic uses. Undoubtedly, ‘African
potato’ is one of the most popular and ethnobotanically
acknowledged medicinal plants in southern Africa
(Drewes and Khan, 2004). Attempts have been made
in some laboratories to isolate, purify and characterize
the chemical constituents of this plant’s corm that could
be responsible for its medicinal properties. One of the
most important chemical constituents of the herb which
has been confirmed to be abundantly present in extracts
of ‘African potato’ is a norlignan diglucoside, hypoxoside,
a biologically inactive pro-drug (Marini-Bettolo et al.,
1982), with an uncommon aglycone structure, consisting
of diphenyl-1-en-4-yne-pentane skeleton (Nair and Kanfer,
2006a; Nair et al., 2007a). Hypoxoside is reported to
have low toxicity, hence, the traditional consumption
of ‘African potato’ as a food (Drewes et al., 1984; Smit
et al., 1995). In the human gut, hypoxoside is converted
to rooperol, a biologically active compound, by beta-
glucosidase enzyme, which is abundantly present in the
human gut and rapidly dividing cancer cells (Mills et al.
2005a) – see Fig. 2.
Both rooperol and its pro-drug, hypoxoside, have been
shown to undergo phase I hepatic metabolism by cyto-
chrome P450 (probably CYP 3A4) enzyme, while their
phase II metabolic products, consisting of diglucuronide,
disulphate and mixed glucuronide-sulphates, are elimi-
nated by first-order kinetics (Albrecht et al., 1995a; Mills
et al., 2005b). Rooperol can be recovered from these
metabolites by deconjugation reactions (Albrecht et al.,
1995b). Most of the therapeutic properties of ‘African
potato’ extracts observed clinically in man and in labo-
ratory animals to date, have been attributed to rooperol
(Albrecht et al., 1995a; Albrecht et al., 1995b; Vinesi
et al., 1990). Rooperol has been shown to be antineoplas-
tic, bacteriostatic and bactericidal (Drewes et al., 1984;
Drewes and Khan, 2004; Albrecht et al., 1995a). It
has been suggested that the antimetastatic activity of
rooperol could be mediated through its ability to stimu-
late the synthesis of collagen type I that could impede
cell invasions (Dietzsch et al., 1999). However, hypoxo-
side as an oral pro-drug, has failed to exhibit any toxi-
city in phase I clinical trials for cancer therapy (Smit
et al., 1995; Albrecht et al., 1995a; Albrecht et al., 1995b).
Recent laboratory investigations have shown that rooperol
has a strong antioxidant activity, a strong affinity for
phospholipid membranes, and that it inhibits free
radical-induced membrane lipo-oxidation (Laporta et al.,
2007) – see Fig. 1. These findings seem to suggest that
rooperol is important in the maintenance of cell mem-
brane stability (Hostetmann et al., 2000), a phenomenon
Copyright © 2008 John Wiley & Sons, Ltd. Phytother. Res. 23, 147–152 (2009)
DOI: 10.1002/ptr
150 P. M. O. OWIRA AND J. A. O. OJEWOLE
Figure 2. Structures of hypoxoside, rooperol and
β
-sitosterol. The biologically inactive norlignan diglucoside, hypoxoside, is
deconjugated and converted by
β
-glucosidase enzyme to form the biologically active aglucone, rooperol.
which may partially explain its activity against neoplastic
cells.
It is still unclear at the moment, whether the ability
of rooperol to inhibit inflammatory processes in vitro
and in vivo, is as a consequence of its direct ability to
inhibit the production of pro-inflammatory cytokines,
tumour necrosis factor (TNF)-
α
, and interleukins; or
due to its inhibitory effects on enzymes involved in
the synthesis of pro-inflammatory mediators, such as
leukotrienes and prostaglandins. In an earlier study,
Van der Merwe et al. (1993) showed that rooperol is
a potent inhibitor of lipo-oxygenase (an enzyme that
catalyses the first-step in the conversion of arachidonic
acid to leukotrienes), but not cyclooxygenase (COX),
which catalyses the rate-limiting step in the conversion
of arachidonic acid to prostaglandins (Fig. 1). Subse-
quent study by Guzek et al. (1996), in an investigation
which attempted to highlight the potential therapeutic
benefit of ‘African potato’ extracts in the treatment of
airways inflammatory diseases, showed that rooperol
and its derivatives inhibit the production of TNF-
α
,
interleukin1-
β
and interleukin-6, and also suppress the
production of nitric oxide in vitro. However, direct
inhibitions of COX-1 (constitutive) and COX-2 (induc-
ible) isoforms of the COX enzymes by extracts of H.
hemerocallidea corm, have also recently been reported
(Gaidamashivili and Van Staden, 2006; Steenkamp
et al., 2006). Despite the prevailing uncertainties about
the precise mechanism/s by which rooperol exerts its
antiinflammatory effects, it is important to recognize
that rooperol shares intimate structural similarity with
a well-known, strong antioxidant, nordihydroguairectic
acid (Nair et al., 2007b), and comparably inhibits leuko-
triene and prostaglandins synthesis in polymorpho-
nuclear leukocyte and platelet microsomes, respectively
(Van der Merwe et al., 1993; Coetzee et al., 1996). On
the strength of the available scientific, pharmacological
and clinical evidence, several patents have been registered
on rooperol, and the extract has also been registered
under the trade name of ‘Harzol’ in Germany for the
treatment of prostate cancer (Pegel, 1979; Tyler, 1986;
Drewes and Lieberg, 1987; Albrecht et al., 1995a; Nair
et al., 2007a). At present, there are numerous commercial
herbal preparations which contain rooperol or extracts
of ‘African potato’ in the market for the treatment,
management and/or control of many modern and 21st
century diseases of man (Nair et al., 2007a).
Among the chemical constituents of ‘African potato’,
phytosterols have been suggested to be partly responsi-
ble for some of the observed therapeutic and pharma-
cological properties of the corm’s extracts. Mohamed
and Ojewole (2003) attributed the hypoglycaemic effect
of ‘African potato’ extracts observed in streptozotocin-
induced diabetic rats to phytosterols and sterolins in
the extracts of ‘African potato’. Phytosterols are known
to stabilize plant cell membranes (Nair and Kanfer,
2006b), and are also known to have many therapeutic
benefits, including enhancement of immune system
in immunocompromised individuals (Bouic et al., 2001;
Van Wyk et al., 2002; Nair and Kanfer, 2006b). The
antiprostatic adenoma activity attributed to extracts of
‘African potato’, has also been ascribed to phytosterol
glycosides, mainly
β
-sitosterol glycosides (Hostetmann
et al., 2000). These claims, however, remain speculative
in view of the fact that daily intake of the same amounts
of phytosterols and their glycosides from other plant
sources have not produced the same magnitude of thera-
peutic effects (Hostetmann et al., 2000).
TOXICITY
A recent laboratory report has indicated that chronic
infusion of ‘African potato’ extracts may cause a decrease
in glomerular filtration rate, and can elevate plasma
creatinine concentrations in rats, suggesting an impair-
ment of kidney function (Musabayane et al., 2005). No
‘AFRICAN POTATO’: A PLANT-MEDICINE FOR MODERN DISEASES? 151
Copyright © 2008 John Wiley & Sons, Ltd. Phytother. Res. 23, 147–152 (2009)
DOI: 10.1002/ptr
further reports are available in the biomedical litera-
ture to corroborate or dispute this observation. Studies
based on experimental animal models have also shown
that aqueous extracts of ‘African potato’ may cause
bradycardia and brief hypotension (Ojewole et al., 2006)
in guinea-pigs and rats in vitro and in vivo, respectively;
while rooperol has been reported to increase myocardial
contractility in vivo in baboons, possibly due to its catechol
structure (Coetzee et al., 1996). It has been suggested,
however, that these cardiovascular effects of ‘African
potato’ extracts may be clinically benign (Albrecht et al.,
1995a). The case report of a patient with a known his-
tory of ischaemic heart disease who presented with
ventricular tachycardia after chronic ingestion of aque-
ous extract of ‘African potato’ may be a strong evidence
for cardio-toxicity associated with cardio-active chemi-
cal compounds present in ‘African potato’ extracts (Ker,
2005). In South Africa, the national Department of Health
(DoH) recently prematurely terminated a clinical study
on ‘African potato’ extracts in HIV-positive patients due
to a controversial report of ‘bone marrow suppression’
in some of the patients (Mills et al., 2005a). At present,
it is difficult to clarify these claims, given the charged
atmosphere of HIV/AIDS politics in South Africa.
‘AFRICAN POTATO’ EXTRACTS–DRUG
INTERACTIONS
Potential drug interactions between extracts of ‘African
potato’ and antiretroviral drugs have been reported
(Mills et al., 2005b). ‘African potato’ extracts have been
reported to inhibit CYP3A4 isoform of cytochrome P450
and drug transporter protein (P-glycoprotein). Further-
more, ‘African potato’ extracts have been claimed
to activate drug nuclear receptor pregnane X (PXR)
which modulates expressions of both CYP3A4 and
P-glycoprotein (Mills et al., 2005b) – see Fig. 1. Many
antiretroviral drugs are substrates of CYP3A4, and some
herbal preparations are known to alter blood levels
of these drugs through their effects on CYP3A4 and
P-glycoprotein (Mills et al., 2005c). ‘African potato’
extracts, therefore, could potentially interact with HIV
drug-metabolizing enzymes (Mills et al., 2005a). A re-
cent study (Nair et al., 2007a) which compared various
extracts and commercial formulations of ‘African potato’
extracts interestingly showed that only stigmasterol and
rooperol had inhibitory effects on CYP3A4, CYP3A5
and CYP19-mediated drug metabolism. In addition,
the study showed that hypoxoside significantly induced
P-glycoprotein, compared with ritinovir®. Fairly recent
studies (Kuehl et al., 2001; Williams et al., 2002) have
also shown that CYP3A5 may represent more than 50%
of the total CYP3A isoforms of cytochrome P450 in some
individuals, and that CYP3A5 has a higher incidence
among southern African populations (Williams et al.,
2002). CYP19, also known as aromatase, has been
implicated in the development of truncal obesity and
increased adiposity (due to inhibition of oestrogen
synthesis) in patients taking antiretroviral drugs (Toda
et al., 1996). No studies have yet been reported about
the effect of ‘African potato’ extracts on organic cation
transporters (OCT). It is not unreasonable to specu-
late, however, that since up-regulation of pregnane
X nuclear receptor has been reported, it is likely that
‘African potato’ extracts would have an effect on
cellular drug transport systems (Fig. 1). Taken together,
these observations, even though largely in vitro, seem
to suggest possible in vivo interactions between
‘African potato’ extracts and antiretroviral drugs.
Patients taking ‘African potato’ extracts concurrently
with antiretroviral drugs may, therefore, be at risk of
developing adverse events which may lead to treatment
failure, viral resistance and/or drug toxicity.
CONCLUSION
The therapeutic attributes and pharmaco-chemical
profiles of ‘African potato’ (H. hemerocallidea corm)
extracts have been reviewed. From available folkloric,
anecdotal and laboratory evidence, ‘African potato’
extracts contain some chemical compounds with anti-
inflammatory, antidiabetic, antineoplastic, antiinfective
and antioxidant activities. It is highly unlikely that all
these potential medicinal properties of ‘African potato’
extracts could be attributed solely to rooperol and
stigmasterol, which are the two main biologically active
chemical constituents of the herb so far identified. It is
possible that these chemical compounds act in concert
together with other compound/s yet to be identified.
Certainly, more laboratory and clinical studies are re-
quired to clarify this situation. However, the tendency
to irrationally commercialize these findings by way of
seeking patents, or packaging of the known chemical
constituents, may negate genuine efforts to unravel the
potential therapeutic mystery of this ‘miracle’ medicinal
plant.
REFERENCES
Abdool-Karim SS, Ziqubu-Page TT, Arendse R. 1994. Bridging the
gap: potential for a healthcare partnership between African
traditional healers and biomedical personnel in South Africa.
S A Med J 84(Suppl): S1–S16.
Albrecht CF, Kruger PB, Smit BJ et al. 1995a. The pharma-
cokinetic behaviour of hypoxoside taken orally by patients
with lung cancer in phase I trials. S Afr Med J 85: 861–865.
Albrecht CF, Theron EJ, Kruger PB. 1995b. Morphological char-
acteristics of the cell-growth inhibitory activity of rooperol
and pharmacokinetic aspects of hypoxoside as an oral
prodrug for cancer therapy. S Afr Med 85: 853– 860.
Amusan OOG, Sukati NA, Dlamini PS, Sibandze FG. 2007. Some
Swazi phytomedicines and their constituents. Afr J Biotech
6: 276 –272.
Bouic PJ, Clark A, Brittle W, Lamprecht JH, Freestone M,
Lieberberg RW. 2001. Plant sterol/sterolin supplement use
in a cohort of South African HIV-infected patients: effects
on immunological and virological surrogate markers. S Afr
Med J 91: 848– 890.
Coetzee JF, Kruger PB, Albrecht CF, Jahed N, van Jaarsveld PP.
1996. Pharmacokinetic behaviour and cardiovascular effects
of intravenously administered hypoxoside and rooperol.
Arzneimittelforchung 46: 997–1000.
Dietzsch E, Albrecht CF, Parker MI. 1999. Effect of rooperol on
collagen synthesis and cell growth. IUBMB Life 48: 321–325.
Drewes SE, Khan F. 2004. The African potato (Hypoxis hemer-
ocallidea) a chemical-historical perspective. S Afr J Sci 100:
425– 430.
Copyright © 2008 John Wiley & Sons, Ltd. Phytother. Res. 23, 147–152 (2009)
DOI: 10.1002/ptr
152 P. M. O. OWIRA AND J. A. O. OJEWOLE
Drewes SE, Lieberg RW. 1987. Rooperol and its Derivatives. US
Patent No. 4644085.
Drewes SE, Hall AJ, Learmonth RA, Upfold UJ. 1984. Isolation
of hypoxoside from Hypoxis rooperi and synthesis of (E)-1,
5-bis (3,4-dimethoxyphenyl) pent-4-en-1-yne. Phytochemistry
23: 1313–1316.
Feng L, Xia Y, Garcia GE, Hwang D, Wilson CB. 1995. Involvement
of reactive oxygen intermediates in cyclooxygenase-2 expres-
sion induced by interleukin-1, tumour necrosis factor-alpha,
and lipopolysaccharide. J Clin Invest 95: 1669–1675.
Gaidamashivili M, van Staden J. 2002. Interaction of lectin-like
proteins of South African medicinal plants with Staphyloc-
occus aureus and Bacillus subtilis. J Ethnopharmacol 80:
131–135.
Gaidamashivili M, van Staden J. 2006. Prostaglandin inhibitory
activity by lectin-like proteins from South African plants. S
Afr J Bot 71: 661–663.
Guzek A, Nizaankowska E, Allison AC, Kruger PB, Koj A. 1996.
Cytokine production in human and rat macrophages and
dicatechol rooperol and esters. Biochem Pharmacol 52: 991–
998.
Hostetmann K, Martson A, Ndjoko K, Wofender JL. 2000. The
potential of African plants as a source of drugs. Curr Org
Chem 4: 973–1010.
Hutchings A, Scott AH, Lewis G, Cunningham AB. 1996. Zulu
Medicinal Plants – An Inventory. University of Natal Press:
Pietermaritzburg; 55.
Ker J. 2005. Ventricular tachycardia as an adverse effect of
the African potato (Hypoxis spp.). Cardiovasc J S Africa 16:
55.
Kuehl P, Zhang J, Lin Y et al. 2001. Sequence diversity in CYP3A
promoters and characterization of the genetic basis of poly-
morphic CYP3A5 expression. Nat Genet 2: 383 –391.
Kumagai T, Kawamoto Y, Nakamura Y et al. 2000. 4-Hydroxy-2-
nonenal, the end product of lipid peroxidation, is a specific
inducer of cyclooxygenase gene expression. Biochem Biophys
Res Commun 273: 437–441.
Laporta O, Pérez-Fons L, Mallavia R, Caturla N, Micol V. 2007.
Isolation, characterization and antioxidant capacity assess-
ment of the bioactive compounds derived from Hypoxis
rooperi corm extract (African potato). Food Chem 10: 1425–
1437.
Mahomed IM, Ojewole JAO. 2003. Hypoglycemic effect of H.
hemerpcallidea corm (African potato) aqueous extracts rats.
Meth Find Exp Clin Pharmacol 25: 617–623.
Mander M. 1998. Marketing of Indigenous Medicinal Plants in
South Africa: A Case Study in KwaZulu-Natal. Food Agri-
culture Organization: Rome.
Marini-Bettolo GB, Patamia M, Nicoletti M, Galeffi C, Messana I.
1982. Hypoxoside, a new glycoside of uncommon structure
from Hypoxis obtuse Bush. Tetrahedron 38: 1683–1687.
Mills E, Cooper C, Seely D, Kanfer I. 2005a. African herbal
medicines in the treatment of HIV: Hyoxis and Sutherlandia.
An overview of evidence and pharmacology. Nutr J 4: 19–
24.
Mills EJ, Foster BC, van Heeswwijk RP et al. 2005b. Impact of
African herbal medicines on antiretroviral metabolism. AIDS
19: 95 –107.
Mills E, Montori V, Peri D, Philips E, Koren G. 2005c. Natural
health product-HIV drug interactions: a systemic review.
Int J STD AIDS 16: 181–186.
Morris K. 2002. South Africa tests traditional medicines. Lancet
Infect Dis 2: 319.
Musabayane CT, Xozwa K, Ojewole JAO. 2005. Effects of
Hypoxis hemerocallidea (Fisch. & C.A. Mey) [Hypoxidaceae]
corm (African potato) aqueous extract on renal electrolyte
and fluid handling in the rat. Renal Failure 2: 763–770.
Nair VPD, Dairam A, Agbonon A, Arnason JT, Foster BC, Kanfer
I. 2007a. Investigation of the antioxidant activity of African
Potato (Hypoxis hemerocallidea corm). J Agric Food Chem
55: 1707–1711.
Nair VPD, Foster BC, Arnason JT, Mills EJ, Kanfer I. 2007b. In vitro
evaluation of human cytochrome P450 and P-glycoprotein-
mediated metabolism of some phytochemicals in extracts
and formulations of African potato. Phytomedicine 14: 498–
507.
Nair VDP, Kanfer I. 2006a. High-performance liquid chromatographic
method for the quantitative determination of hypoxoside in
African potato (Hypoxis hemerocallidea) and in commercial
products containing the plant material and/or its extracts.
J Agric Food Chem 56: 2816 –2821.
Nair VPD, Kanfer I. 2006b. Determination of
β
-sitosterol and
stigmastanol in oral dosage forms using high performance
liquid chromatography with evaporative light scattering
detection. J Pharm Biochem Anal 41: 731–737.
Ojewole JAO. 2002. Anti-inflammatory properties of Hypoxis
herocallidea corm (African potato) extracts in rats. Meth
Find Exp Clin Pharmacol 24: 685– 687.
Ojewole JAO. 2006. Antinociceptive, anti-inflammatory and
antidiabetic properties of Hypoxis hemerocallidea Fisch. &
C.A. Mey (Hypoxidaceae) corm [‘African Potato’] aqueous
extracts in mice and rats. J Ethnopharmacol 103: 126 –134.
Ojewole JAO, Kamadyaapa DR, Musabayane CT. 2006. Some in
vitro and in vivo cardiovascular effects of Hypoxis hemero-
callidea Fisch & CA Mey (Hypoxidaceae) corm (African
potato) aqueous extract in experimental animal models.
Cardiovasc J S Afr 17: 166 –171.
Pegel KH. 1979. Active Plant Extracts of Hypoxidaceae and Their
Uses. US Patent No. 16387.
Puckree T, Mkhize M, Mgobhozi Z, Lin J. 2002. African tradi-
tional healers: what healthcare professionals need to know.
Int J Rehab Res 25: 247–251.
Pujol J. 1990. Naturafrica – The Herbalist Handbook. Jean Pujol
Natural Healers’ Foundation: Durban.
Singh Y. 1999. Hypoxis: yellow stars of horticulture, folk remedies
and conventional medicine. Veld Flora 85: 123–125.
Smit BJ, Albrecht CF, Lienberg RW et al. 1995. A phase I trial of
hypoxoside as an oral prodrug for cancer therapy – absence
of toxicity. S Afr Med J 85: 865– 870.
Southern Africa Development Community (SADC). 2002. SADC
Ministerial Consultative Meeting on Nutrition and HIV/AIDS.
SADC: Johannesburg.
Steenkamp V, Gouws MC, Gulumian M, Elgorashi EE, van
Staden J. 2006. Studies on antibacterial, anti-inflammatory
and anti-oxidant activity of herbal remedies used in the
treatment of benign prostatic hyperplasia. J Ethnopharmacol
103: 71–75.
Toda K, Nomoto S, Shizuta Y. 1996. Identification and charac-
terization of transcriptional regulatory elements of the human
aromatase cytochrome P450 gene (CYP19). J Steroid
Biochem Mol Biol 56: 196 –199.
Tyler VE. 1986. Plant drugs in the twenty-first century. Econ Bot
40: 279.
Van der Merwe MJ, Jekkins K, Theron E, van de Walt BJ. 1993.
Interaction of dicatechold rooperol and nordihydroguaiaretic
acid with oxidative systems in the human blood: A structure-
activity relationship. Biochem Pharmacol 45: 303–311.
Van Wyk B-E, Van Outshoorn B, Gericke N. 2002. Medicinal
Plants of South Africa, 2nd edn. Briza Publications: Pretoria;
156–157.
Vinesi P, Serafini M, Nicoletti M, Spano L, Betto P. 1990. Plant
regeneration and hypoxoside content in H. obutusa. J Nat
Prod 53: 196 –199.
Williams JA, Ring BJ, Cantrell VE et al. 2002. Comparative
metabolic capabilities of CYP3A4, CYP3A5, and CYP3A7.
Drug Metab Dispos 30: 883– 891.
... H. hemerocallidea of the hypoxidaceae family is an indigenous Southern African plant, found abundantly in South Africa, Swaziland, Lesotho, and Botswana. The plant, commonly known as 'African potato', 'miracle plant', 'molic', and 'star flower' is enlisted in Southern Africa as an indigenous medicinal plant with potential health benefits [83]. The plant is characterized by strap-like hairy leaves, yellow star-shaped flowers, and thick green hairy stems. ...
... Also, H. hemerocallidea is laced with trace elements including, copper, zinc, and manganese, thus used as pro-fertility supplements. Evidence-based laboratory investigation indicated that extracts obtained from African potato possess numerous pharmacological properties including antidiabetic, anti-inflammatory, antioxidant, antihypeglycemic, analgesic, and anticancer [83]. ...
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... However, hypoxoside was found to be pharmacologically inactive on its own but is usually converted to its aglycon, rooperol, through hydrolysis of the former by the action of a β-glucosidase enzyme in the human gut ( Figure 1) [28]. Rooperol, on the contrary, has fascinating biological activities such as anti-inflammatory, anticancer [29] antibacterial, immunomodulatory, antioxidant, antitumor, and anti-convulsant activities [30]. Therefore, there is a need to find other ways by which hypoxoside can be more valuable, especially looking at its quantity from HH extract. ...
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... However, this compound can be produced on an industrial scale from Chlorophytum borivilianum [17]. Nevertheless, it is unlikely that the medicinal benefits provided by the African potato are solely due to rooperol and stigmasterol [18]. There are numerous other secondary plant metabolites that could contribute to the medicinal properties of the African potato. ...
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... Hypoxis hemerocallidea is still currently abundant and of least conservation concern (Williams et al., 2019). However, extensive loss of grassland through land-use change (Jewitt et al., 2015) will reduce its future range while extensive harvesting of the corm for a wide range of traditional and commercial medicinal purposes (Khan and Drewes, 2004;Owira and Ojewole, 2009;Matyanga et al., 2020) depletes local populations, especially around urban centres (Dold and Cocks, 2002;Mofekeng et al., 2020). Plants with large corms are becoming less available in the wild because of overharvesting (Williams et al., 2007). ...
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... Hypoxis hemerocallidea is still currently abundant and of least conservation concern (Williams et al., 2019). However, extensive loss of grassland through land-use change (Jewitt et al., 2015) will reduce its future range while extensive harvesting of the corm for a wide range of traditional and commercial medicinal purposes (Khan and Drewes, 2004;Owira and Ojewole, 2009;Matyanga et al., 2020) depletes local populations, especially around urban centres (Dold and Cocks, 2002;Mofekeng et al., 2020). Plants with large corms are becoming less available in the wild because of overharvesting (Williams et al., 2007). ...
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Mesic grasslands in South Africa (> 650 mm a-1 MAP) are rich in herbaceous forbs, which outnumber grass species by more than 5 to 1. Many of these forbs have underground storage units (USOs), such as thickened rootstocks, rhizomes, bulbs, or corms, that provide resources (non-structural carbohydrates, minerals, and water) enabling them to resprout after dry, frosty winters, and fire. However, despite their extensive biomass and reserves ostensibly protected underground, geophytic mesic grassland forbs can be severely depleted or extirpated by chronic trampling and grazing of their aerial parts by livestock. This study examined a possible explanation for forb demise in overgrazed grassland by investigating, in a pot trial, whether the growth of forbs and the size of their USOs are negatively affected by simulated green leaf loss. In a 2x2 factorial (clipped vs. unclipped x spring regrowth in the dark vs. light), five replicate plants of Hypoxis hemerocallidea, a common mesic grassland forb that resprouts from a corm, were subject to six severe (clipped to 80 mm) defoliations during the growing season and regrown in spring under full or restricted light to measure stored reserve contribution to regrowth. Defoliated plants were resilient to defoliation during the growing season, matching the total biomass production of unclipped plants, though cutting reduced the number of leaves by ~60% and flowers by almost 85%. Spring regrowth on stored reserves equalled that from reserves plus concurrent photosynthesis, indicating the value of USOs for regrowth. However, there was a marked carry-over effect of previous season defoliation, resulting in a one-third reduction in shoot growth and 40% fewer inflorescence in spring. Crucially, corm mass was more than halved by clipping. Above-ground spring growth was linearly related to corm mass. It was concluded that buried stored reserves are not protected by recurrent disturbance to aerial plant parts and that continued diminishment of USOs under chronic disturbance by overgrazing or frequent mowing would weaken and likely eventually kill plants, reducing forb species richness. Lenient management by infrequent summer mowing or grazing at moderate stocking rates combined with periodic rotational full season resting and dormant-season burning is recommended to maintain the USOs and vigour of forbs in mesic grassland
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