Ethnobotanical survey of some medicinal important leafy vegetables in North Western Nigeria

This paper focuses on twenty-eight medicinally important leafy vegetables documented from the North Western part of Nigeria. It also highlights their medicinal importance in the treatment of minor ailments as well as their sources. The family Compositae (Asteraceae) contained the highest number of plants, followed by Cucurbitaceae, Malvaceae and Solanaceae. Sixty eight percent of the documented vegetables are cultivated, 11% is usually obtained in the wild, while 21% is either cultivated or obtained from the wild. The need for concern on the conservation of genetic resources of these plants (especially those in the wild) is stressed in order to safeguard them for future generations and avoid their genetic erosion. The establishment of a gene/seed bank for vegetables is advocated.


INTRODUCTION
There is currently a global attention on the conservation and sustainability of the rich biodiversity of the tropical rainforest.This is as a result of the vast resources derivable from the forest and the threat to ecosystem due to degradation and consequent unsustainable use of resources.The potential of the Nigerian flora as a veritable source for pharmaceuticals and other therapeutic materials have been emphasized (Gbile and Adesina, 1986).Medicine constitutes one of the many resources of the forest on which the health of the average African population depend since the time of creation.Herbs have usually served as the repository of healing materials and have been acknowledged to be generally saved without or with minimum side effects (Gbile and Adesina, 1986).Many vegetable crops particularly the leafy vegetables are mainly consumed for their nutritional values without much consideration for their medicinal importance.There are several varieties of these leafy vegetables either in the wild or under cultivation in the rural areas.The age of civilization which influenced the drastic migration to urban centres has however had a great influence on the choice of vegetables used as food.
This gradual loss of genetic diversity of vegetables deprives man of the opportunity to meet the future and even present challenges of vegetable production for the enhancement of health of the individual.Herbs have usually constituted the main repository of drugs and many have been known not to pose any threat to human life.They, apart from healing, provide the necessary nutrients for health and development of the human body.In time past, the average African rural dweller depended on subsistence farming in which he cultivated vegetable crops at least for his immediate family consumption.
Man more than ever before needs a re-orientation on the sustainable use of his natural resources, particularly in this era of economic recession to source raw materials for medicine and harness the abundant rich flora for an improved Primary Health Care Delivery.

MATERIALS AND METHODS
A market survey was carried out for the available leafy vegetables.Ten markets, namely, Sokoto, Bodinga, Birnin-kebbi, Argungu, *Corresponding author.E-mail: samdiri@yahoo.co.uk.Gusau, Talata-Mafara, Katsina, Futua, Kano and Gwarzo all in North Western part of Nigeria were visited for the purpose of this survey.The types of leafy vegetables on sale were recorded.Informal interview was conducted with some of the market women as to the variety of vegetables and where and how they are obtained for sale in the markets.
Identification of the plant samples was done in the field (markets), while others which could not be readily identified were brought to the herbarium of the Department of Biological Sciences, Usmanu Danfodiyo University Sokoto.The medicinal values of the identified plants were obtained from relevant literature (Dalziel, 1948;Schippers, 2000).

RESULTS
This paper documents 28 medicinally important leafy vegetables and their therapeutic uses.Emphasis has been mainly on the leaves of the plants since these are usually consumed.However, trees whose leaves are used as vegetables as well as medicine are not included e.g.Adansonia digitata, Moringa oleiferae and Triplochiton scleroxylon.Other parts of the plants such as stem, seeds, fruits and flowers in some cases are also useful medicinally.The family Compositae/Asteraceae has the highest recorded number of plants (21%) followed by the Cucurbitaceae (14%) and Malvaceae and Solanaceae (11%).Sixty eight percent of the documented vegetables are cultivated, 11% are usually obtained in the wild, while 21% are either cultivated or obtained from the wild.Table 1 shows the diverse medicinal uses of the plants.

DISCUSSION
The result of this study shows a great diversity of therapeutically useful leafy vegetables in the Nigerian flora.It also indicates the potentials of these plants in enhancing both the nutrition and health care of average Nigerians in the face of harsh economic crisis.How far these plants can be used to achieve the aforementioned objectives will depend largely on the extent they can be utilized The current global attention on the conservation and sustainability of biodiversity (particularly the subsavannah region) is a consequence of the threat posed to life.This is as a result of the degradation and unsustainable use of the abundant forest resources.
The degradation of the environment calls to question our knowledge of biodiversity, particularly, plant diversity which is vital to human survival.Such knowledge is essential in the discovery of new sources of drugs, food, and other useful plant resources.The taxonomist is thus being confronted by urgent questions on the identification, nomenclature, classification and distribution of plants as well as their ecology and use (Kapoor-vijay and Lucas, 1992).According to Hedberg and Hedberg (1992), an indispensable pre-requisite for national conservation is to know which species need protection and where they occur.Conservation biologist in Nigeria must begin to address conservation at the genetic level which is in the view of Heywood (1992), the most neglected and least understood area of biological diversity.Ayodele (1996) suggested a working co-operation among taxonomists, conservationists and geneticists to obtain maximum results for biodiversity conservation.
About 60% of the documented leafy vegetables are available in the rural areas including the 11% obtained from the wild.Even so, only a fraction of the other 40% is known to the urban population and contributes to its diet.The 11% obtained in the wild are the most endangered when their habitats are subjected to developmental activities by man.Recent studies have identified the value of Africa's indigenous vegetables for subsistence and income-generating opportunities (Schippers, 2000;Muhammad and Amusa, 2005) and this calls for the flow of information on them for the purposes other than nutrition.The establishment of a gene bank for these vegetables will safeguard the future availability of their genetic resources which could be supplied for cultivation in gardens for subsistence and cash generation.

Table 1 .
List of some leafy vegetables with their medicinal importance.