Qualitative Analysis of the Pyrrolizidine Alkaloids from 11 Asteraceae and Boraginaceae Used in Traditional Medicine in Cote dIvoire
Witabouna Mamidou Kone
Pyrrolizidine Alkaloids (PAs) are toxic for human and livestock. Worldwide many episodes of human PA intoxications are well reported. This study aimed at assessing the presence of PAs in some Asteraceae and Boraginaceae used in traditional medicine in Cote dIvoire to treat various diseases such malaria, infant cure, microbial infections. TLC detection with Ehrlich reaction method of Mattocks was used to screen 11 plant species, Ageratum conyzoides L. (Asteraceae), Aspilia africana (Pers.) C.D. Adams (Asteraceae), Bidens pilosa L. (Asteraceae), Chromolaena odorata L. (Asteraceae), Erigeron floribundus (Kunth) Sch. Beep (Asteraceae), Emilia praetermissa Milne-Redh (Asteraceae), Heliotropium indicum L. (Boraginaceae), Synedrella nodiflora (L.) Gaertn (Asteraceae), Tridax procumbens L. (Asteraceae), Vernonia cinerea L. (Asteraceae) and Vernonia colorata (Willd) Drake (Asteraceae). All these plants were found to contain at least trace amount of PAs. The richest species were H. indicum, T. procumbens and V. colorata. The presence of PAs in the studied plants is an indication of people exposure to probable toxicity. This warrants assessment of risk related to the consumption of such plants in Cote dIvoire as medicinal herbs.
to cite this article:
Witabouna Mamidou Kone and Brahima Kande, 2012. Qualitative Analysis of the Pyrrolizidine Alkaloids from 11 Asteraceae and Boraginaceae Used in Traditional Medicine in Cote dIvoire. Research Journal of Phytochemistry, 6: 75-83.
Received: December 06, 2011;
Accepted: February 17, 2012;
Published: March 26, 2012
Since ancient time, plants have been used by human for various needs including
food and health care. In Africa, people rely heavily on medicinal plants for
curing diseases (Garba et al., 2007). Nowadays,
nature still provides more reliable source of medical agents. Almost 40% of
currently available drugs are direct or indirect derivatives of natural precursors
(Sohail et al., 2011). In some Asian and African
countries, the use of herbal remedies containing plant and other materials are
an integral part of traditional culture, with approximately 80% of the population
(WHO, 2008), relying on such remedies for primary health
care. Some consider that medicines based on herbal formulations usually have
lesser side effects and better compatibility with human body than modern medicines
(Upadhyay et al., 2011). The consumption of natural
medicines is relatively safer than that of synthetic drugs (Saputera
et al., 2006).
Safety is the most important consideration before administration of herbal
products. Contrary to popular perception that medicinal plants are safe, profound
toxicity can result from their use (Moss, 1998; Bateman
et al., 1998). Despite their growing popularity as naturally safe
with bioactive products, very little information is available on the safety
of medicinal herbs (Sulaiman et al., 2010), in
particular in West African countries. From time to time, plants are discovered
to be toxic for both human and animal (Younis and Adam,
2008). In many countries, medical practitioners and local people are not
aware of the toxicity of remedies. They still use medicinal plants without anxiety.
However, some plants that may cause intoxication are Pyrrolizidine alkaloid-containing
plants. Alkaloids are natural plant products which are sometimes toxic to animals
(Holstege et al., 1995) and human when eaten.
For example, cryptolepine, the major alkaloid of the roots of Cryptolepis
sanguinolenta, a medicinal plant used in Ghana for treating malaria, was
shown to provoke toxicity in mammalian cells (Ansah et
Interest in the pyrrolizidine alkaloid (PAs) content of plant species is obviously
stimulated by the fact that pyrrolizidine alkaloidosis is a serious problem
for livestock production and human (Stegelmeier et al.,
1999). Pyrrolizidine alkaloid-containing plants are widely distributed in
the world and are probably the most common poisonous plants affecting livestock,
wildlife and humans.
These alkaloids and their N-oxides occur as natural components of many herbal
preparations, cooking spices and honey and can contaminate food crops and animal-derived
food (Edgar, 2003; Cao et al.,
2008). Humans can become inadvertently exposed through consumption of contaminated
food and herbal remedies. Chronically ingesting low levels of pyrrolizidine
alkaloids and/or their N-oxides can be source of intoxication.
The potential toxicity of pyrrolizidine alkaloids containing plants is well
documented. The major effect of dietary pyrrolizidine alkaloids and chronic
exposure on humans is hepatic veno-occlusive disease, leading to cirrhosis and
eventually irreversible liver damage (IPCS, 1988; Zuckerman
et al., 2002; Fu et al., 2004; Wiedenfeld
et al., 2008).
The widespread use of medicinal plants in many West African countries such as Cote dIvoire indicates possible human exposure to hepatotoxic and carcinogenic PA. This situation warranted studies on these plants to assess their possible toxicity.
Most PA-containing plants are found in three plant families, namely Boraginaceae,
Asteraceae and Leguminosae (Cheeke, 1988). A current
search of the literature does not reveal any detailed report on the pyrrolizidine
alkaloid content of medicinal plants from Cote dIvoire. We therefore,
reported herein the pyrrolizidine alkaloid content of 11 Asteraceae and Boraginaceae
used in traditional medicine in Cote dIvoire. These plants are Chromolaena
odorata, Aspilia africana, Vernonia colorata, Vernonia
cinerea, Erigeron floribundus, Bidens pilosa, Heliotropium
indicum, Tridax procumbens, Emilia praetermissa, Synedrella
nodiflora and Ageratum conyzoides.
MATERIALS AND METHODS
Selection of studied plant species: The 11 studied plants were selected
after an ethnobotanical review on Asteraceae and Boraginaceae used in Cote dIvoire
and other West African countries for the treatment of various pathological conditions
(Watt and Breyer-Brankwijk, 1962; Bouquet
and Debray, 1974; Adjanohoun and Ake Assi, 1979;
Djeneba, 1982; Adjanohoun and Ake
Assi, 1989; PHARMEL, 1992; Hladik
et al., 1996; Tra Bi, 1997; Arbonnier,
2002; Kone, 2003; Adoukou, 2007;
Idu and Onyibe, 2007; Adou, 2008;
Apema et al., 2007).
The selection of these species was based on 3 criteria namely the use in traditional
medicine, accessibility and lack of information on the presence of pyrrolizidine
alkaloids for most of these plant species. H. indicum (Souza
et al., 2005), C. odorata (Biller
et al., 1994) and A. conyzoides (Wiedenfeld,
2011) were included because data on samples from other ecological zones
were available on PA content.
Ten of these plants are from the family of Asteraceae and 1 from Boraginaceae (Table 1).
Alkaloid extraction: The leaves, stems and whole plants of selected plants were collected in Abidjan from September 2010. The samples were dried during 2 weeks under air-conditioned room (18°C) and then grounded in a mortar to obtain powders.
For alkaloid extraction, 5 g of powder were moistened with 5 mL of NaOH solution
10%. This mixture was extracted with 50 mL of dichloromethane, under mechanical
stirring during 24 h (Fig. 1). The macerates were filtered
on Whatman paper. The filtrates obtained were evaporated to dryness and lyophilized
to remove all traces of solvent. Extract solutions (10 mg mL-1) were
prepared by dissolving 10 mg of extract in dichloromethane and methanol (1/9;
Detection of pyrrolizidine alkaloids: TLC using Ehrlich reaction method
of Mattocks is the most useful colorimetric method for potentially hepatotoxic
pyrrolizidine compounds (Mattocks, 1986; Mattocks
and Nwude, 1988). It is specific for pyrrolizidine alkaloids and is not
useful for any other alkaloids. This is a quick, sure and easy method for a
qualitative detection of PAs (Wiedenfeld, 2011). This
qualitative test was used for detection of pyrrolizidine alkaloids in organs
of the 11 Asteraceae and Boraginaceae species. The presence of alkaloids is
important, as it is the first indication that the species may be toxic (Nuhu
et al., 2009).
Twenty microliter of extracts (10 mg mL-1) were applied on aluminum backed Silicagel 60 F254 and developed in mobile phase hexane-ethyl acetate (1:1). After development, chromatograms were dried and then sprayed with Ehrlich reagent (1 g of p-dimethylalaminobenzaldehyde/100 mL of ethanol/15 mL of concentrated chlorhydric acid). After heating at 95°C during 15 min, pyrrolizidine alkaloids appear as blue or purple spots (Fig. 1).
|| Alkaloid extraction and analysis
|| Some utilization of studied asteraceae and boraginaceae species
in traditional medicine (Source: Literature)
RESULTS AND DISCUSSION
The TLC screening of studied plants for presence of pyrrolizidine alkaloids revealed that all contained at least trace amount of PAs (Table 2). The richest plant species were Heliotropium indicum, Tridax procumbens and Vernonia colorata. T. procumbens leaves showed 3 spots while its stems with flowers indicated 4 spots corresponding to PAs. For H. indicum, leaves and roots present 3 spots each.
The remaining plant contained less quantity or trace of pyrrolizidine alkaloids. This was the case of Ageratum conyzoides, Aspilia africana, Emilia praetermissa, Bidens pilosa, Chromolaena odorata, Erigeron floribundus, Vernonia cinerea and Synedrella nodiflora.
Phytochemicals are non-nutritive plant chemicals that have protective or diseases
preventive properties (Karthishwaran et al., 2010).
Although, useful and beneficial for health, certain of these phytochemicals
such as PAs can be dangerous for human due to their hepatotoxicity and nephrotoxicity.
The PAs cause acute and chronic hepatic affections, in particular, the hepatic
veno-occlusive affections (Willmot and Robert, 1920;
Wiedenfeld et al., 2008).
|| Pyrrolizidine alkaloid-containing studied plants
|+: Present, ++: Abundant
We consequently assessed the presence of PAs in 11 Asteraceae and Boraginaceae
species used in traditional medicine in Cote dIvoire. All these plants
showed at least trace amount of pyrrolizidine alkaloids. This study is the first
report of the pyrrolizidine alkaloid content of the studied plant species apart
from H. indicum, C. odorata and A. conyzoides.
Previous studies have shown the presence of PAs in these 3 plants. The rationale
for selecting samples of H. indicum, C. odorata
and A. conyzoides from Cote dIvoire for this study arose
from the fact that variation of phytochemical content could occur according
to ecological and growth conditions. The results obtained in this study for
samples from Cote dIvoire are in full agreement with the previous reports
of the PA content of H. indicum, C. odorata and
H. indicum is popular medicinal plant used in many countries
such as Cote dIvoire (Kamanzi, 2002) and Brazil
(Souza et al., 2005) for health care needs. However,
in Costa Rica, this species has been implicated as the most probable principal
cause of massive mortality in horses due to intoxication by pyrrolizidine alkaloids
from the plant (Van Weeren et al., 1999). The
presence of PAs in H. indicum was also reported for a sample of
Brazil (Souza et al., 2005).
Ageratum conyzoides has been found to be responsible for actual incidents
with toxic PA problem in Ethiopia (Wiedenfeld, 2011).
A. conyzoides is widespread and the seeds of this weed can contaminate
millet. This plant is medicinal plant, but also a containing toxic PAs. A.
conyzoides is used in Edo State, Nigeria for treating stomach pain in
children, ulcer, headache and dysentery (Idu and Onyibe,
2007). Study on the toxicity of A. conyzoides showed that
the extract at doses of 500 and 1000 mg kg-1 administered orally
and daily for a one month period did not show any toxic effects in rats (Igboasoiyi
et al., 2007). This study was based on lethal dose determination
and evaluation of serum levels of some enzymes and biomolecules. According to
results obtained, Igboasoiyi et al. (2007) have
concluded that A. conyzoides is safe for use in ethnomedicine.
However, the presence of PAs indicates a probable risk which might be assess.
In this study, C. odorata leaves present trace of PAs. This tropical
weed has been shown to contain the N-oxides of five pyrrolizidine alkaloids.
Highest concentration was found to occur in roots and mature flower heads, while
leaves and stems are almost devoid of alkaloids and no PAs are present in nectar
(Biller et al., 1994). The data on leaves is
in agreement with the content of this plant part observed in the present study.
Even considered as toxic compounds, some PAs could have interest in fighting
against diseases. PAs are class of secondary plant metabolites that are active
in defense against herbivore and microorganism. Interestingly, pure PAs from
C. odorata have nematicidal effects on root-knot nematode Meloidogyne
incognita (Thoden et al., 2007). Also, a
study has reported the interest of the indicine N-oxide, a PAs, in the treatment
of patients with advanced cancer (Ohnuma et al.,
1982). Also PAs have possible interest in agriculture. Timbilla
et al. (2008) have shown that dry chopped roots of C. odorata
could serve as effective PA-lures for the development of PA-based attracticides
for the management of Zonocerus variegatus. This variegated grasshopper
is a serious pest of agriculture and forestry in sub Saharan Africa.
For the other species, previous phytochemical screening has revealed presence
of class of alkaloids. This is the case of E. floribundus (Asongalem
et al., 2004), V. colorata (Gasquet
et al., 1985), T. procumbens (Jude
et al., 2009; Mundada and Shivhare, 2010;
Agrawal et al., 2010), V. cinerea (Maheshwari
et al., 2007), S. nodiflora (Bhogaonkar
et al., 2011), B. pilosa (Geissberger
and Sequin, 1991; Deba et al., 2008) and
A. africana (Okwu and Josiah, 2006; Abii
and Onuoha, 2011).
The presence of PAs in studied plants indicates a probable toxicity. We plan to extend this work to a great number of Asteraceae and Boraginaceae used in traditional medicine as medicinal herbs and food, to isolate and elucidate structure of PAs of plants that contain this class of alkaloids.
The authors sincerely thank Centre Suisse de Recherches Scientifiques en Cote dIvoire for Laboratory infrastructures.
Abii, T.A. and E.N. Onuoha, 2011.
The chemical constituents of the leaf of Aspilia africana
as a scientific backing to its tradomedical potentials. Agric. J., 6: 28-30.CrossRef | Direct Link |
Adjanohoun, E. and L. Ake Assi, 1979.
Contribution to the recording of medicinal plantsfrom Cote d'Ivoire. Ministry of Scientific Research, Centre National de la Floristique, Abidjan (Cote d'Ivoire).
Adjanohoun, N.E. and L. Ake Assi, 1989.
Traditional medicine and pharmacopeia. Contribution to Floristic and Ethnobotanical Studies in Benin, ACCT, Paris (France).
Adou, B.L.A., 2008.
Utilization of medicinal plants during pregnancy in Agni women, N'denye S/P Yakasse Feyasse (Eastern Cote D'Ivoire), Master. University of Abobo-Adjame, Abidjan.
Adoukou, A.S., 2007.
Inventory of plants from Ivorian Pharmacopeia and their modes of utilization for the treatment of diabetes in Abidjan city (Cote d'Ivoire) Master. University of Abobo-Adjame, Abidjan.
Agrawal, S., S. Khadase and G. Talele, 2010.
Bioactive immunomodulatory fraction from Tridax procumbens
. Asian J. Biol. Sci., 3: 120-127.CrossRef | Direct Link |
Apema, A.K.R., D. Mozouloua, E. Kosh-Komba and Y. Ngoule, 2007.
Contribution to the knowledge of medicinal plants used for treating hypertension by Traditional practitioners of Bangui and surrounding areas. Proceedings of the 18th AETFAT Congress, February 26-March 2, 2007, Yaounde, Cameroon. -
Ansah, C., E.A. Mfoafo, E. Woode, C. Opoku-Okrah and W.K.B.A. Owiredu, 2008.
Toxicological evaluation of the anti-malarial herb Cryptolepis sanguinolenta
in rodents J. Pharmacol. Toxicol., 3: 335-343.CrossRef | Direct Link |
Arbonnier, M., 2002.
Trees, Shrubs and Liana of Dried Zones from West Africa. CIRAD, Montpellier, France, Pages: 57
Asongalem, E.A., H.S. Foyet, J. Ngogang, G.N. Folefoc, T. Dimo and P. Kamtchouing, 2004.
Analgesic and antiinflammatory activities of Erigeron floribundus
. J. Ethnopharmacol., 91: 301-308.CrossRef |
Bateman, J., R.D. Chapman and D. Simpson, 1998.
Possible toxicity of herbal remedies. Scott-Med. J., 43: 7-15.CrossRef | Direct Link |
Bhogaonkar, P.Y., M.J. Dagawal and D.S. Ghorpade, 2011.
Pharmacognostic studies and antimicrobial activity of Synedrella nodiflora
(L.) gaertn. Biosci. Dis., 2: 317-321.Direct Link |
Biller, A., M. Boppre, L. Witte and T. Hartmann, 1994.
Pyrrolizidine alkaloids in Chromolaena odorata
: Chemical and chemoecological aspects. Phytochemistry, 35: 615-619.CrossRef | Direct Link |
Bouquet, T. and M. Debray, 1974.
Medicinal Plants from Cote d'Ivoire. Orstom Publisher, Paris, France
Cao, Y., S.M. Colegate and J.A. Edgar, 2008.
Safety assessment of food and herbal products containing hepatotoxic pyrrolizidine alkaloids: Interlaboratory consistency and the importance of N-oxide determination. Phytochem. Anal., 19: 526-533.PubMed |
Cheeke, P.R., 1988.
Toxicity and metabolism of pyrrolizidine alkaloids. J. Anim. Sci., 66: 2343-2350.PubMed |
Deba, F., T.D. Xuan, M. Yasuda and S. Tawatu, 2008.
Chemical composition and antioxidant, antibacterial and antifungal activities of the essential oils from Bidens pilosa
Linn. var. Radiata. Food Control, 19: 346-352.CrossRef | Direct Link |
Djeneba, B., 1982.
Contributions to the study of Vernonia colorata
(Willd.) leave drake. Ph.D. Thesis, University of Marseille, France.
Edgar, J.A., 2003.
Pyrrolizidine alkaloids and food safety. Chem. Aust., 70: 4-7.
Fu, P.P., Q. Xia, G. Lin and M.W. Chou, 2004.
Pyrrolizidine alkaloids-genotoxicity, metabolism enzymes, metabolic activation and mechanisms. Drug Metab. Rev., 36: 1-55.PubMed |
Garba, S.H., J. Prasad and U.K. Sandabe, 2007.
Hepatoprotective effect of the aqueous root-bark extract of Ficus sycomorus
(Linn) on carbon tetrachloride induced hepatotoxicity in rats. J. Boil. Sci., 7: 276-281.CrossRef | Direct Link |
Gasquet, M., D. Bamba, A. Babadjamian, G. Balansard, P. Timon-David and J. Metzger, 1985.
Amoebicidal and anthelmintic action of vernolid and hydroxyvernolid isolated from the leaves of Vernonia colorata
. Eur. J. Med. Chem. Chim. Ther., 20: 111-115.
Green, B.O., 2007.
Significance end efficacy of medicinal plants in the Niger Delta. Cont. J. Pharm. Sci., 1: 23-29.Direct Link |
Hladik, C.M.A., H.H. Pagezy, O.F. Linares, G.J.A. Koppert and A. Froment, 1996.
Food in Tropical Forest: Biocultural Interactions and Development Perspectives. UNESCO, Paris, France
Holstege, D.M., J.N. Seiber and F.D. Galey, 1995.
Rapid Multiresidue screen for alkaloids in plant material and biological samples. J. Agric. Food Chem., 43: 690-699.CrossRef |
Idu, M. and H.I. Onyibe, 2007.
Medicinal plants of Edo state, Nigeria. Res. J. Med. Plant, 1: 32-41.CrossRef | Direct Link |
Igboasoiyi, A.C., O.A. Eseyin, N.K. Ezenwa and H.O. Oladimeji, 2007.
Studies on the toxicity of Ageratum conizoides
. J. Pharmacol. Toxicol., 2: 743-747.CrossRef | Direct Link |
Jude, C.I., C.I. Catherine and M.I. Ngozi, 2009.
Chemical Profile of Tridax procumbens
Linn. Pak. J. Nutr., 8: 548-550.CrossRef | Direct Link |
Pyrrolizidine Alkaloids. World Health Organization, Geneva Switzerland,
Kamanzi, A.K., 2002.
Medicinal plants from Cote d'Ivoire: Phytochemical investigations directed by biological assays. Ph.D. Thesis, University of Cocody, Abidjan, Cote d'Ivoire.
Karthishwaran, K., S. Mirunalini, G. Dhamodharan, M. Krishnaveni and V. Arulmozhi, 2010.
Phytochemical investigation of methanolic extract of the leaves of Pergularia daemia
. J. Biol. Sci., 10: 242-246.CrossRef | Direct Link |
Kone, M., 2003. In vitro
evaluation of antibacterial activity of Chromolaena odorata
L. against bacteria in buruli ulcer. Master Thesis, University of Abobo-Adjame, (Cote d'Ivoire).
Maheshwari, P., B. Songara, S. Kumar, P. Jain, K. Srivastava and A. Kumar, 2007.
Alkaloid production in Vernonia cinerea
: Callus, cell suspension and root cultures. Biotechnol. J., 2: 1026-1032.CrossRef | PubMed | Direct Link |
Mattocks, A.R., 1986.
Chemistry and Toxicology of Pyrrolizidine Alkaloids. Academic Press, Orlando, USA
Mattocks, A.R. and N. Nwude, 1988.
Pyrrolizidine alkaloids from Crotalaria lachnosema
and C. naragutensis
. Phytochemistry, 27: 3289-3291.CrossRef |
Moss, T.M., 1998.
Herbal medicines in the emergency-a primer for toxicities and treatment. J. Emerg. Nurs., 24: 509-513.
Mundada, S. and R. Shivhare, 2010.
Pharmacology of Tridax procumbens
a Weed: Review. Int. J. PharmTechnol. Res., 2: 1391-1394.Direct Link |
Nuhu, H., E.M. Abdurrahman and M. Shok, 2009.
Comparative analysis of the alkaloids of three Crotalaria
species. Nig. J. Pharm. Sci., 8: 54-58.
Ohnuma, T., K.S. Sridhar, L.H. Ratner and J.F. Holland, 1982.
Phase I study of indicine N-oxide in patients with advanced cancer. Cancer Treat Rep., 66: 1509-1515.PubMed |
Okwu, D.E. and C. Josiah, 2006.
Evaluation of the chemical composition of two Nigerian medicinal plants. Afr. J. Biotechnol., 5: 357-361.Direct Link |
Oluyemi, K.A., U.C. Okwuonu, D.G. Baxter and T.O. Oyesola, 2007.
Toxic effects of methanolic extract of Aspilia africana
leaf on the estrous cycle and uterine tissues of wistar rats. Int. J. Morphol., 25: 609-614.Direct Link |
Database of Traditional Medicine and Pharmacopeia of African and Oceanic India Countries. ACCT, Paris, France
Saputera, D. Mangunwidjaja, S. Raharja, L.B.S. Kardono and D. Iswantini, 2006.
Gas chromatography and gas chromatography-mass spectrometry analysis of Indonesian Croton tiglium
seeds. J. Applied Sci., 6: 1576-1580.CrossRef | Direct Link |
Sohail, M.N., F. Rasul, A. Karim, U. Kanwal and I.H. Attitalla, 2011.
Plant as a source of natural antiviral agents. Asian J. Anim. Vet. Adv., 6: 1125-1152.CrossRef |
Souza, J.S.N., L.L. Machado, O.D.L. Pessoa, R. Braz-Filho and C.R. Overk et al
Pyrrolizidine alkaloids from Heliotropium indicum
. J. Braz. Chem. Soc., 16: 1410-1414.Direct Link |
Stegelmeier, B.L., J.A. Edgar, S.M. Colegate, D.R. Gardner, T.K. Schoch, R.A. Coulombe and R.J. Molyneux, 1999.
Pyrrolizidine alkaloids plants, metabolism and toxicity. J. Nat. Toxins., 8: 95-116.PubMed |
Sulaiman, S.M., G. Rajashekhar, P.J. Prakash, D.S. Singh and C. Saleem, 2010.
Evaluation of safety and immunotoxicity of immunol, a polyherbal formulation in rats. J. Pharmacol. Toxicol., 5: 262-274.CrossRef |
Timbilla, J.A., K. Yeboah-Gyan and B.W. Lawson, 2008.
Attraction of Zonocerus variegatus
(Orthoptera: Pyrgomorphidae) to pyrrolizidine alkaloids: A potential novel approach to its management. J. Entomol., 5: 103-112.CrossRef | Direct Link |
Thoden, T.C., M. Boppre and J. Hallmann, 2007.
Pyrrolizidine alkaloids of Chromolaena odorata
act as nematicidal against and reduce infection of lettuce roots by Meloidogyne incognita
. Nematology, 9: 343-349.CrossRef | Direct Link |
Tra Bi, F.H., 1997.
Utilization of plants in classified forest of Haut-Sassandra and Scio, in Cote d'Ivoire. Ph.D. Thesis, University of Cocody, Abidjan (Cote d'Ivoire).
Upadhyay, H.C., D.C. Saini and S.K. Srivastava, 2011.
Phytochemical analysis of Ammannia multiflora
. Res. J. Phytochem., 5: 170-176.CrossRef |
Van Weeren, P.R., J.A. Morales, L.L. Rodriguez, H. Cedeno, J. Villalobos and L.J. Poveda, 1999.
Mortality supposedly due to intoxication by pyrrolizidine alkaloids from Heliotropium indicum
in a horse population in Costa Rica: A case report. Vet. Q., 21: 59-62.PubMed |
Watt, J.M. and M.G. Breyer-Brandwijk, 1962.
The Medicinal and Poisonous Plants of Southern and Eastern Africa. 2nd Edn., E and S Liningstone Ltd., London, UK., Pages: 1457
Traditional medicine. WHO Fact Sheet No. 134, WHO., Geneva. http://www.who.int/mediacentre/factsheets/2003/fs134/en/.
Wiedenfeld, H., 2011.
Plants containing pyrrolizidine alkaloids: Toxicity and problems. Food Addit. Contam. Part A, 28: 282-292.CrossRef | Direct Link |
Wiedenfeld, H., E. Roeder, T. Bourauel and J. Edgar, 2008.
Pyrrolizidine Alkaloids: Structure and Toxicity. V and R Unipress, Gottingen, Germany
Willmot, F.C. and G.W. Robert, 1920. Senecio
disease or cirrhosis of the liver due to Senecio
poisoning. Lancet, 196: 848-849.CrossRef |
Younis, S.I. and S.E.I. Adam, 2008.
Evaluation of toxicity of Rhanterium epapposum
in Wistar rats. J. Pharmacol. Toxicol., 3: 134-140.CrossRef | Direct Link |
Zuckerman, M., V. Steenkamp and M.J. Stewart, 2002.
Hepatic veno-occlusive disease as a result of a traditional remedy: Confirmation of toxic pyrrolizidine alkaloids as the cause, using an In vitro
technique. J. Clin. Pathol., 55: 676-679.CrossRef |
Geissberger, P. and U. Sequin, 1991.
Constituents of Bidens pilosa
L.: Do the components found so far explain the use of this plant in tradicinal medicine?. Acta Trop., 48: 251-261.CrossRef | Direct Link |