Diversity of medicinal plants used in the treatment of skin diseases in Tabuk region , Saudi Arabia

Saudi Arabia has a unique floral diversity due to its remarkable diversity in the ecological habitats. Many plant species are widely applied in traditional medicine to treat several diseases. In the present study, ethnobotanical survey of plant species in Tabuk Region (Saudi Arabia) was carried out describing their uses in treating skin diseases. The results showed that a total of 51 plants species belonging to 40 genera and 28 families were reported. The richest families terms of number of species were Asteraceae, Boraginaceae and Chenopodiaceae (4 species, 7.84% for each) followed by Euphorbiaceae, Fabaceae and Zygophlyllaceae (3 species, 5.88% for each). Most of the plant species collected in this study are in the life form of herbs and shrubs and comprise 74% of the plant species. On the other hand, the most frequent plant parts used to treat skin diseases are whole plant (51%) and leaf (24%). The flora diversity in Tabuk Region is obviously threatened by anthropogenic activities and the public authorities should start thinking seriously about the conservation of these important natural resources.


INTRODUCTION
Arabian Peninsula include many countries; it is acceptable fact that the biodiversity of plant species in Saudi Arabia is amongst the richest flora in Arabian Peninsula.This comprises a valuable and important genetic source for medical plants in the Middle East (Rahman et al., 2004).The diversity of plants in Saudi Arabia is due to its unique habitats that stretch along large spatial area.A total of 2250 species (including pteridophytes and gymnosperms) in 142 families are represented in the flora of the Kingdom of Saudi Arabia.Of these, there are 242 endemic and 600 rare and endangered species in the wild (Collenette, 1999).However, the diversity of plants in Saudi Arabia and specifically Tabuk region is threaten by several human activities such as woodcutting, agriculture and the invasion of exotic species (Al-Mutairi et al., 2016).
Medical plants are considered an important economic resource of natural biodiversity.These medical plants can be exploited appropriately to produce essential drugs.Furthermore, these natural resources should be conserved and protected with sustainable management.The fact of using plants in traditional medicine started E-mail: nalharbi@ut.edu.sa.Tel: +966144565677 thousands years ago and this knowledge has been inherited from one generation to another.There are several studies about the medicinal use of plants in treating different diseases (Rahman et al., 2004;Al-Sodany et al., 2013;El-Mawla et al., 2016;Al-Harbi, 2017;Shinwaikar et al., 2004), and many studies carried out in some Asian countries about using medicinal plants to cure skin diseases such as India (Sanjeet et al., 2012;Mudasir, 2014;Balaraju et al., 2015), while there are a few studies about using medicinal plants traditionally to treat skin diseases such as scabies, eczema and healing wounds in Saudi Arabia.
Due to the importance of the plants in the treatment of skin diseases and In the light of paucity of the information in this regard, this study was conducted to highlight on the wild plants and their medical uses to treat skin diseases in Tabuk region, Saudi Arabia.

Study area
The surveying of plant species was carried out in several habitats (Sand dunes, valleys, mountains, gravel lands and coastal lands) of Tabuk region which is situated in the North west part of Saudi Arabia with approximate area of 117000 km 2 .The climate in this region is extremely arid with very low annual rainfall of less than 40 mm/year.According to several floral and ecological studies conducted in this region, this region is characterized with unique habitats and remarkable plant diversity (Al-Mutairi et al., 2016).

Surveying the plants
The plant species of medical importance to treat skin diseases were surveyed in various sites of Tabuk region (Tabuk City, Tayma, Duba, Haql, Al-Wajh and Umluj) (Figure 1).And then the plant species were classified using the available taxonomical keys and description by Chaudhary (2001), Collenette (1999), Migahid (1996) and Cope (1985).To Identify of the collected plants species for their uses to treat skin diseases was carried out using the description by Rahman et al. (2004), Al-Shanwani (1996), ElMawla et al. (2016) and Al-Sodany et al. (2013).

Data collection
The study area was divided into six sites in each site there are five locations, in each location four plots were taken (10 m ×10 m) for each plot, then the plant species were listed.
A total of 120 sample plots were selected in area under study (Tabuk region).Locations and sample plots were selected to represent a wide range of environmental variation.In each location, sample plots were selected randomly.The sampling process was carried out during the spring season 2016 when most species were expected to be growing.

Data analysis
The plant species were collected in this study were listed and species richness of the plant families, percentage of the plant parts and the percentage of the life forms of the plant species used to treat skin diseases were indicated.

Diversity of medicinal plants in the study area
In the study, a total of 51 species belonging to 40 genera and 28 families were reported for their traditional medical application in Tabuk region, Saudi Arabia.Table 1 presented the number of the species in each family with percentage of their contribution to total number of plant species recorded.The families of Asteraceae, Boraginaceae and Chenopodiaceae were the richest families (4 species, 7.84% for each family).Therefore, these three families constituted almost 25% of the total number of plant species reported to treat skin disease in Tabuk region.However, the families; Euphorbiaceae, Fabaceae and Zygophlyllaceae were reported secondly as richest families (3 species, 5.88% for each family).
The plant species reported in this study are widely known to be used to treat skin diseases in Tabuk region.Table 2 summarizes the percentage of the plant parts that is used for this purpose.Most of these medical plants are used as "whole plant" as the percentage of this application is 51%.Then, plant leafs were secondly important in their application to treat skin diseases in Tabuk region.

Plant parts used
Plant parts used to treat skin diseases in Tabuk region is given in Figure 2 and Tables 2 and 3.

Relationship between this study and the past studies
The present study aimed to survey plant species in Tabuk Region (Saudi Arabia), so it was carried out describing their uses in treating skin diseases, so it will be added and completed to the several studies that surveyed application of plants in treating different human diseases such as digestive system diseases (Rahman et al., 2004) described 86 plant species of medicinal importance with dominance of seven families.However, Al-Sodany et al. ( 2013) described 261 plant species which are commonly used in traditional medicine from Taif.In addition Korpenwar (2012), Egharevoa and Ikhatua (2008) Helene and Sandy (2013), Balaraju et al. (2015) and Manish et al. (2012) studied the role of medicinal plants to treat skin diseases.

Plant diversity
In this study, a total of 51 plant species belonging to 40 genera and 28 families were collected from Tabuk Region (North West of Saudi Arabia) and were identified for their traditional application to treat skin diseases.The number of plants species collected from Tabuk region that used to treat skin diseases is higher compared to other related studies.For instance Balaraju et al. (2015) and Erhenhi et al. (2016) reported only 21 plant species and Egharevba and Ikhatue (2008) reported 41 and Manish et al. ( 2012) reported 23 plant species which are used to treat skin diseases.In the present study, the life form of herbs was the most dominant and constitutes almost 45% followed by shrubs 29%.This is in agreement with the study of Egharevba and Ikhatue (2008) which reported 42% herbs and 26% shrubs, while it is not in agreement with the study of Erhenhi et al. (2016) which reported the life form trees was the most dominant life form followed by herbs.

Part used
According to the available information, the active ingredients of these plants are certain phytochemical compounds that results in ultimate physiological action on human body.Some of these phytochemical compounds are plants alkaloids, saponin, tannins flavonoids, carbohydrates and phenolic compounds (Edeoga et al., 2005).As shown in the present study findings, the most frequent plant part used to treat skin diseases in Tabuk is whole plant (51%) and leaf (24%), This corresponds with the study carried out by Helene and Sandy (2013) was showed that leaf 31%.This is despite the fact that for herbal medicine preparations, different parts of plants can be used such as leaves, bark, stems, roots, fruits and flowers (Egharevba and Ikhatue, 2008).According to Algasim et al. (2013), leaves are the most frequent part used to treat skin diseases in Zari and Zari (2015) and Korpenwar (2012) reviewed the application of four plant species; aloe (Aloe vera), oat (Avena sativa), turmeric (Curcuma longa) and chamomile (Matricaria chamomilla) applied to treat eczema.It was concluded that these four plant species have strong potential for treating eczema

Figure 1 .
Figure 1.Map of the study area (Tabuk region) from Saudi Arabia.

Figure 2 .
Figure 2. The percentage of the life forms of the plant species used to treat skin diseases in Tabuk.

Table 1 .
Species richness of the plant families that used to treat skin diseases in Tabuk region, Saudi Arabia.

Table 2 .
The Percentage of the plant parts used to treat skin diseases in Tabuk region, Saudi Arabia.