Ethnobotanical Leaflets 13: 1273-87. 2009.
Phytochemical Analysis of Medicinal Plants Used for the Management of Hypertension by Esan people of Edo State, Nigeria
J.K. Mensah, R I. Okoli ,1 A. A. Turay,2 and E.A. Ogie-Odia
Department of Botany
1Department of Pharmacology and Therapeutics
2Department of Medical Laboratory Sciences
Ambrose Alli University, P.M.B 14, Ekpoma, Nigeria
Issued 01 October 2009
is one of the principal health problems in the society and a leading cause of
cardio-vascular deaths in various communities worldwide. Over 33 plants and
their products have been reported in
Key words; Medicinal plants, hypertension, phytochemistry.
Hypertension is one of the principal health problems in the society and an important cause of cardio-vascular deaths in various communities worldwide. It is a silent - killer whose onset of complications is insidious. Such complications as cardiac remodeling, hypertrophy, renal impairment, nephropathies and ocular complications such as retinopathies and cardiovascular accident or stroke (Benowitz, 2001) are associated with hypertension.
Traditionally the use of plant parts as source of herbal preparations for treatment of various ailments are based on the experience passed from generation to generation, virtually by oral tradition and through practice and forms part of the indigenous knowledge of people of any locality (Olowofela, 1991; Sofowora, 1993). Most of these herbal remedies are known by our traditional healers and elderly men and women of families in our rural areas. The herbal knowledge or practices known by traditional healers are jealously guarded with utmost secrecy for economic reasons. According to Obute (2007), many traditional herbal practitioners also tend to hide the identity of plants used for different ailments largely for fear of lack of patronage should the patient learn to cure himself. Thus to mystify their trade, cultivation of the plant is not encouraged, consequently collection is virtually from the wild.
Fortunately, some elders of the rural societies do willingly impart this knowledge to interested people sometimes on payment of an inducement fee and this has helped in the propagation of some herbal knowledge in this country. Infusions and decoctions have historically been the traditional dosage forms for orally administered medicinal plants. These infusions and decoctions are usually good for extracting water soluble active ingredients such as glycosides, mucilage, alkaloids, polysaccharides and tannins, but are limited by their unpleasant taste, shelf life; and the poor solubility of many phytochemicals in water. As a result, many modern herbal practitioners prefer tinctures and fluid extracts to infusions and decoctions. The use of alcohol / water mixture as solvent is efficient in extracting a wide variety of active ingredients. In addition alcohol is a good preservative for herbal preparations compared to water. Many herbal preparations are yet to be scientifically investigated. Some of the plants also contain potentially poisonous substances including mutagens, and carcinogens whose long term adverse effect may not be immediately obvious to the herbalists (Awosika, 1993). The authors of this report are not unmindful of the fact that like all other drugs some of the various herbal preparations are likely to have adverse effects. Furthermore, the concomitant ingestion of herbs and drugs or different herbal preparations is also of particular concern as there is potential for herb-drug or herb-herb interaction to occur (GHP 2007).
A number of medicinal plants abound in Nigeria’s flora (Gbile, 1986) which is the richest country in West Africa with regards to medicinal plant resources. The country exhibits a wide range in terms of climate and topology which has a bearing on its vegetation and floristic composition. Some of the information on these medicinal plants are in books written by Dalziel (1937, 1948) Oliver, (1960), Ayensu (1978), Sofowora (1982, 1993) Gbile (1986), Gill (1992), Awosika, (1993), Iwu, (1993), Kafaru (1994), Dokosi, (1998), and Odugbemi (2006) Other records on herbs that are used to manage common ailments in Nigeria are scattered in the works of Adegoke et al. (1968 ), Gbile and Adesina (1987), Anonymous, (1993), Obute (2007), Okoli et al. (2007) and Mensah et al. (2008) among others.
Herbal preparations are used in traditional medicine as crude drugs in various dosage forms, as whole, crushed, powdered forms, decoctions, dried extracts, infusions, poultices and tinctures (GHP 2007). Many of these plants have been investigated in recent times and found to contain active substances that are medically useful, whereas many more are yet to be scientifically investigated. A number of plant extracts used by natives in various parts of the world as arrow and ordeal poisons were later found to contain cardiac glycosides useful for the treatment of heart failure while others like physostigmine from the seed of Physostigma venenosun from Nigeria affect cardiac functions and are used in ordeal trials (Lawrence et al 1997 ). Rauwolfia serpentina which contains the alkaloid reserpine, was perhaps the first herbal preparation used for the treatment of hypertension. A West African species R. vomitoria has been used for treating the same disease and other ailments by local herbalists for a long time. This species gives much higher yield than R. serpentina but yet to be exploited commercially. The drug Digitalis was mentioned in literature in 1250B.C in the writings of Welsh physicians. Until recently, products from Digitalis namely digitoxin and digoxin which are pure glycosides were the popular drugs for the management of congestive heart failure (Ghani, 1986, Ayitey Smith, 1989). Currently, diuretics and calcium chemical blockers have taken over as the drugs of choice for the treatment of the ailment in orthodox medicine.
Traditional health practitioners in Esanland regularly employ a large
number of tropical plants in various herbal preparations to manage different
ailments endemic to the area. Their sources include common vegetables/fruits,
leaves and root/stem barks of endemic plants. The purpose of this publication
is to provide a bibliographical source for the study of various plants for
the treatment of hypertension in
Materials and Methods
Survey of literature
An initial literature survey was undertaken to enumerate herbal plants used in the management of hypertension in West-Africa with emphasis on Nigeria. Local and national publications were assessed and then documented to serve as bibliographical source for the study of various plants for the treatment of hypertension.
Survey of medicinal plants used for managing hypertension in Esanland, Edo State.
Patients who had records of the ailment volunteered information about various herbal homes where they received treatments. Consequently, relevant data were generated by visits to the herbal homes and twelve elderly women in ten settlements in Esanland where the patients had directed the researchers to obtain indigenous knowledge for the management of hypertension, were interviewed. The herbalists were accompanied to the bush/forest for direct collection of plants used for the management of hypertension. The information about the local names, usages, parts of plants used, methods of preparation and administration of plants was obtained from local healers, herbalists, experienced parents and patients by filling in questionnaires during personal interviews with them.
Further literature search was undertaken to corroborate the claims by
traditional healers as to which plants are used to manage hypertension. Plant
samples which were not readily identified in the field were taken to the
Department of Botany,
Collection of Samples and Phytochemical analysis
The fresh plant/plant parts collected through the method describe above were screened, together with their families and vernacular names. The leaves/plant parts were washed under running tap water, and dried in an oven at 700 C for 24 hours. With the aid of mortar, pestle, miller, grinder, these plant parts were homogenized to fine powder and stored in airtight bottles or containers for phytochemical analysis. One gram of powder was subjected to qualitative phytochemical tests for alkaloids (Myers Reagent), saponins (chloroform and H2SO4 tests), inulin (Molischs Reagent) cardiac glycosides (Keller-Kiliani test) and tannins (Ferric salt tests) adopting the procedures described by Stephen (1970); Obute (2007) and Parekh and Chanda (2007).
Results and Discussion
The literature search revealed
about 33 plants which are used for various herbal preparations for the
management of hypertension (Table 1). The list is however not exhaustive but
gives a representation of what is available in West Africa and
The plants which were identified for managing hypertension in the various herbal homes and by the elderly during field collection in Esanland were Psidium guajava, Piper guineense, Loranthus spectobulus, Talinum triangulare, Senna occidentalis, Rauwolfia vomitoria, Allium sativum, Allium cepa, Carica papaya, Euphorbia hirta, Ocimum gratissimum, Persea americana, Peperomia pellucid and Vernonia amygdalina.
Most of the plants used for managing hypertension were of general
distribution and usage in West Africa and elsewhere on the African continent;
while others were limited to specific localities. This confirms the assertion
that traditional healing practices and indeed management of hypertension in
local communities of
A total of 14 plants species distributed in 12 taxonomic families were noted in this work for the management of hypertension in Esanland. The plant species listed (Table 2) have been found useful in the treatment of hypertension and other disease conditions based on the endemic health problems of the different settlements within the study area. Edo State serves as a good reservoir for a variety of plant species and the conservation of medicinal plants because of its rich tropical vegetation which are preserved in 48 forest reserves occupying 23% of the land area of the State (439,139ha ; Azeke, 2002) The part of interest in the majority of the species encountered is the leaf. Included in the list of plant for treating hypertension are edible vegetables such as water leaf, bitter leaf, garlic, climbing black pepper and scent leaf which are available in various open markets within the study area. However, the local herbalists were quick to point out that they do not usually administer leafy vegetables to their patients as remedy for hypertension because their effects are slow. Consequently only patients with mild cases of the disease condition are put on vegetable soups while more potent herbs (mistletoe, pawpaw, bitter and avocado pear leaves) are administered alone or in combinations with other herbs to those with relatively more serious conditions.
In the present study, the plants
which were identified by various herbalists in Esanland for the management of
hypertension were examined for alkaloids, inulins, flavonoids, cardiac
glycosides, tannins and saponins. The results of the various phytochemical
tests revealed that alkaloids,
saponins, inulins , tannins,
flavonoids and cardiac glycosides were present in the plants studied (Table
3). Cardiac glycosides were present in all the species studied while
alkaloids were present in all except A.
sativum, A. cepa, O. gratissimum, P.
The different herbs encountered at the different herbal homes have different
medicinal properties and many of them have multiple uses and hence used for
the management of more than one ailment. Thus Esan people have used some of
these medicinal plants for controlling and managing hypertension and other
types of ailments over the years. Gill (1992) , Anslem ( 2006) and Okoli et al (2007) have reported the
effectiveness of garlic, leaves
of avocado pear, pawpaw, bitter and
mistletoe for the treatment of
hypertension in Nigeria. Similarly, Ayitey - Smith (1989) has reported the
used of avocado pear, and bitter leaf for the management of hypertension and
other disease condition in
Conclusion and Recommendations
Each community in Nigeria and indeed Esanland has its peculiar way of treating different ailments, and many plants are usually found useful for the treatment of common diseases such as hypertension. Efforts should be made at creating medicinal plant gardens and generally encourage the development of medicinal plants as a way of enhancing adequate health care for the people considering the rising incidence of complications and death due to hypertension.. Medicinal plant products still remain the primary source of supply of many important drugs in orthodox medicine today. Since there are so many of these naturally occurring substances of plant origin (which cover a wider range than synthetic chemicals), it is obvious that the plant kingdom offers a better opportunity of providing useful medicinal compounds for the treatment of hypertension. Furthermore, elucidating the chemical structure of active components of herbs also makes room for synthetic modifications for better pharmacokinetic profiles.
It is believed that the plants used by the Esan people of Edo State, Nigeria could be potential sources of drugs if the active ingredients are identified and adequately characterized. Also self reliance (as it relates to local sourcing / manufacturing of drugs) is worth considering as it is an area in which most developing countries have a strong potential which can help to improve the people’s health standard. It is important to remark that traditional medicine is at a transitional stage in the development of modern medicines in developing countries, thus progressive and conscious efforts must be made to accelerate the transformation. Furthermore, intensive and systematic research programmes must be drawn up and implemented for the purpose of accelerating the transformation by putting science into the art of traditional medicine. Until this is achieved, traditional medicine must play a complementary role in our health care delivery system of the indigenous communities in Esanland of Edo State, Nigeria.
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Table 1. Some plants listed for treatment of hypertension in West Africa.
Table 2. Ethno botanical information on Medicinal plant species used in Edo State for the treatment of hypertension.
Table 3. Phytochemical Analysis of Screened Medicinal Plant Species.