Ethnobotanical survey of medicinal plants used in treating viral infections among Yoruba tribe of South Western Nigeria

Ethnobotanical survey of plants used to treat some common viral diseases, such as chicken pox, poliomyelitis, influenza, hepatitis, measles and jaundice was carried out in Ekiti, Ondo, Osun and Oyo States in South Western Nigeria. Questionnaires were distributed among the participants and oral discussions were employed. Two hundred and eight (208) data were collected and tabulated. The Yoruba names, botanical names, methods of preparation and mode of administration of the plants were considered. The research work showed that members of the family Annonaceae (10.3%) were most frequently used, followed by members of Leguminosae (9.9%), and Zingiberaceae (7.9%), for treating chickenpox and measles infections, although all other plants play prominent roles in peoples` health care. Also, knowledge of medicinal herbs was being left in the hands of the elders between the age range of 51-70 years and 71-80 years. The leaves of the plants (45.5%) were mostly used in treating viral infections, followed by the use of stem bark (13.5%). All other parts were less commonly used to treat viral diseases. Mono-prescription was rare in the data collected. Oral application had the highest mode of administration (83.7%), while the combination of both oral and external applications (12.5%) closely followed. Decoction (90.4%) was the most frequently used method of anti-viral herbal preparation, while concoction (0.9%) was least used. Herb sellers (72.6%) constituted the major source of information about the use of anti-viral medicinal herbs, followed by traders, civil servants and herbalists with 17.31, 6.25 and 3.85 respectively. Many plants in the studied area may be a good source of lead molecules needed in viral chemotherapy after extraction of the bioactive components as well as removal of toxic residue following toxicological studies.


INTRODUCTION
Indigenous medicine is now recognized worldwide both by the rural populace and the urban elite as an important healthcare resource.The World Health Organization (WHO) has pointed out that traditional medicine is an important contribution to its health goals.There are considerable economic benefits in the development of indigenous medicine and in the use of medicinal plants for the treatment of various diseases (WHO, 2003).
Medicinal plants have also been of importance in the *Corresponding author.E-mail: chourlar@yahoo.com.
health care system of local communities as the main source of medicine for the majority of the rural population.
Plants have not only nutritional value but also, in the eyes of the local people, they have medicinal and ritual or magical values (Adewunmi et al., 2001).
Plants have been a major source of medicine for human kind.According to available information, a total of at least 35000 plants species are widely used for medicinal purposes.The demand for traditional herbs is increasing very rapidly, mainly because of the harmful effects of synthetic chemical drugs.The global clamor for more herbal ingredients creates possibilities for the local cultivation of medicinal and aromatic crops as well as for the regulated and sustainable harvest of wild plants.Such endeavors could help raise rural employment in the developing countries, boost commerce around the world and perhaps contribute to the health of millions (Anita, 2004).
Nigeria is endowed with an enormous diversity of animals and plants, both domesticated and wild, and an impressive variety of habitats and ecosystems.This heritage sustains the food, medicinal, clothing, shelter, spiritual, recreational, and other needs of her population (Odugbemi and Akinsulire, 2006).
This biodiversity also ensures the essential ecological functions on which life depends, including a steady supply of clean water, nutrient cycling, and soil maintenance.It is the treasure house from which future food needs, cures diseases, and elements for knowledge and technology will be found.Plants have provided the basis for traditional treatment for different types of diseases and still offer an enormous potential source of new chemotherapeutic agent (Adewunmi et al., 2001).This however require extraction of the bioactive molecules of pharmacological importance present following purification and identification procedures as well as toxicological studies.
Therefore it is essential for drugs discovery to preserve and record traditional know -how on medicinal plants and in most cases, this depends on local practitioner and field survey (Anita, 2004).
Even though pharmacological industries have produced a number of new antiviral drugs in the last three decades, resistance to these drugs by microorganisms has increased.The use of plant extracts and phytochemicals being of great significance in therapeutic treatments can however be explored in ameliorating this problem (Erdogrul, 2002;Acharya and Shrivastava, 2008).
The components of ethnomedicine have long been ignored by many biomedical practitioners for various reasons.For example, the chemical composition, dosages and toxicity of the plants used in ethnomedicine are not clearly defined (Lowe et al., 2000).However, it is interesting to note that the ethnomedicinal uses of plants is one of the most successful criteria used by the pharmaceutical industry in finding new therapeutic agents for the various fields of biomedicine (Cox and Balick,1994).
Medicinal plants play a key role in the developed and advancement of modern studies on them has important contributions in the healthcare system of local communities as the main source of medicine for the majority of the rural population.However, there have been dearths of information on the various medicinal plants that are available for treating specifically infections of viral etiology.
The aims and objective of this project is therefore to find medicinal herbs and plants used to treat viral diseases which are cheap and easily accessible since viral infections can be one of the biggest nightmares for Medical Practitioners and patients.

Study area
The study areas consist of Ekiti, Ondo, Osun, and Oyo states of Southwestern Nigeria.The areas consist of residents that are civil servants, traders, and farmers.Southwestern Nigeria lies within longitude 3°E and 5.8°E and latitude 6.4°N and 9.5°N Tropical with variations governed by interaction of moist South-West monsoon and dry North-East winds with mean maximum temperatures of 30-32°C.Annual rainfall decreases northward; about 2,000 mm in coastal zone.

Mode of survey
The methods utilized in obtaining the information on plants used in the treatment of viral diseases in the study include-consulting herbalist, herb sellers, enquiry from villagers about plants/recipes used in the areas, and enquiry from relations.Advocacy visits involving field trips were embarked upon to collect information majorly from herb sellers, traders and few individuals in the states to solicit their support in the study areas.
Data collected as questionnaires were administered through person to person contact in order to identify the plants and to ask major question such as the preparation, mode of administration, and dosage of each plant depending on each state.The informants, majority being illiterate can only communicate through their dialect.Literatures on medicinal plants, vernacular and botanical names were consulted to corroborate the claims by the healers (Sofowora, 1982;Odugbemi and Akinsulire, 2006).
The objectives of the study were explained to the informants.The informed consent was obtained from each of the participants, although among the herb sellers' permission was granted from the head of the herb seller with certain amount of money before information could be unfolded nearly in all the study areas.

RESULTS
The indigenous name is a reflection of the culture and trade name of area where the plants are mostly found.The name given was sometime indicative of the appearance of and use of the plants.The various plants used in treating some common viral diseases, their local names, botanical names and common names are presented in Table 1.
The occurrences of the various families of the plants used are on Table 2.The families Annonaceae, Leguminosae are the most abundant while families such as Compositae, Euphorbiaceae, Zingiberaceae frequency of occurrence was in the intermediate range.However, some in the families, Liliaceae, Poaceae and Curcurbitaceae has low frequency of occurrence.The various plant part utilized are represented on Table 3.The leaf, stem, bark are the most commonly used parts, while fruit, roots are seldomly used.
The age distribution of the informants showed that the elderly in the age range 51 -70 and 71 -80 were the ones that reported information of recipes, while others showed little or no response.This is shown on Table 4.The sources of information in the research are from herbalist, herb sellers, trader and civil servants.The herb sellers are the major source of the information, while the herbalist and civil servant gave less information as depicted by Table 5.The mode of preparation as presented on Figure 1 indicated that decoction was the most common way of preparing these herbs while other methods are less commonly employed.The mode of administration as shown on Figure 2 revealed that drinking was found to be the most preferred mode of administration while rubbing and bathing were less frequently employed.The majority of the people in the study area preferred combination of herbs and modern drugs.However, the uses of herbs alone are not well employed (Table 6).The generality of the populace does not take any precaution in the use of the recipe.However, plants should be washed before taken them.Although using of herbs and drugs at the same time was discouraged as representedon Table 7.The side effects commonly associated with the use of herbal recipe were vomiting and stooling.However, most informants opined that there is not much side effect in taking herbal recipes as shown on Table 8.

DISCUSSION
In the ethnobotanical survey conducted in Ekiti, Ondo, Osun and Oyo States of South Western Nigeria (Figure 3), a number of (208) reported medicinal plants species and their uses in treating some common viral diseases by the rural populace demonstrates the depth of their local indigenous knowledge on medicinal plants and their application.Similar study undertaken in Belvia came up with 129 plant species of medicinal importance.In general, various studies  (Tesfaye and Zemede, 2009).
The study also revealed that Family Annonaceae (10.3%) took the leading, followed by family Legiminosae, Zingiberaceae, Compositae, Liliaceae, Anarcadaceae, Rabiaceae, Poaceaes and Rutaceae, were most commonly mentioned in the study areas.Although recent research in Ogun State showed that Cucurbitaceae is highly effective against Measles (Sonibare et al., 2009).The fact that some of the reported plants are having similar uses in the area elsewhere can be taken as an indication of their pharmacological effectiveness having been tested in different areas by different culture.The emphasis of the synergism of more than one medicinal plant was emphasized by the informants (Wassihun et al., 2003).
Leaf was most commonly used for medicinal purpose than the other plant parts in the study areas.This was followed by the use of stem bark, root, fruit and whole plant, while fruit epicarp, stem bark sap and a combination of leaf and root were least used.Many studies conducted in different parts in Ethiopia and many parts of the world showed that plant leaves are used more than the other parts of a plant.This practice helps to reduce the rate of threat on plant species (Giday et al., 2003).
This study reveals that, most knowledge on herbal remedies is handled down the older members of the community between 51-70 and 71-80 years of age.This hits at the fact that ethnomedicinal knowledge is concentrated in, and relative difficulty in its transfer from the elderly to the younger generation.This might be related to the waning of interest of the young generation on indigenous knowledge.Different studies in different areas showed that medicinal plant knowledge and transfer of knowledge to the young generation have been affected by modernization (having access to modern education and health service) and environmental change (Hillenbrand, 2006).Responses from the informants showed that herbal preparation was up-held only by the herb sellers.Other respondents such as, traders and civil servants showed little or no response.This was due to lack of interest from the community people as a result of easy access to modern drugs and health education.
The study revealed that decoction was the mostly employed method of preparation in the study areas for viral treatment.The results of this study also showed that the use of concoction was not a common practice for some viral treatment in the areas.Some other viral medicinal plants were only prepared on special prescription.Similar studies among the Kani's tribe in India are said to usually prepare medicines from a combination of several plants as they believed that combinations of several plant parts cure diseases rapidly (Ayyanar and Iguacinathu, 2005).
It was observed from the research that there were some disagreements among the informants on the dosage of certain remedies prescribed.The dosage depended on the informant that prescribed the herbs for medicinal purpose.Lack of standardization and precision on dosage and quality control is seen as one of the main disadvantages of traditional medicine as summarized from various sources (Sofowora, 1982).Also in the study areas, oral applications took the upper hand, followed by a combination of both external and oral administration, depending of the type of viral infection and informant's prescription.This is similar to a study conducted in Bolivia which shows that, the most frequently used route of administration is oral ingestion (Hunde et al., 2004).
The toxicity of some medicinal plants and their potentials to cause harm were a common complaint among those who would like traditional medicine to be standardized.It is commonly believed that traditional    practitioners either do not know the strength of their own medicines or do not bother to fix doses to the size or body weight of the patients (Tesfaye and Zemede, 2009).

Conclusion
The result of the study revealed that there was high diversity of medicinal plants and traditional knowledge about the use, preparation, and application of which is still maintained in the South western Nigeria.However, the knowledge of herbal medicine was held by elders.The decline in the use of plants by the younger generation may gradually lead to the fading away of indigenous knowledge associated with the plants.

RECOMMENDATIONS
There is a need for validation and standardization of phytomedicines and traditional medical practices so that this sector can be accorded it rightful place in the health care system.Government should provide a global forum for growers, traders, manufacturer of herbal medicine and professionals in the field of traditional and alternative therapies to share knowledge, experiences and ideas.Scientists, therefore should rise to get the knowledge from the elders and encourage the herb sellers to register with the government agency and make them available so that herbal medicine could easily be accessible and cheap for the less privileged.Further research should be carried out to confirm the

Figure 3 .
Figure 3. Map of Nigeria indicating study area.

Table 1 .
Plants used in the treatment of viral diseases.

Table 2 .
Occurrence of various families of medicinal plants surveyed.

Table 3 .
Plant parts used for treating viral infections.

Table 4 .
The distribution of informants in age -classes.

Table 5 .
Sources of information.

Table 6 .
Preference for the use of herbs or modern drugs.

Table 7 .
Precautions for the use of herbal recipe.

Table 8 .
Side effects in the use of herbal recipes.