Ethnobotanical and Ecological Studies of Plants Used in the Treatment of Diabetes in Kwango, Kongo Central and Kinshasa in the Democratic Republic of the Congo

Non-communicable diseases represent new challenges for the mankind in the fight for health improvement. Among these diseases, diabetes is a major contributor. Diabetes is a serious chronic disease that occurs when the pancreas does not produce enough insulin or when the body is unable to use the insulin produced effectively. This survey was performed in Kwango, Kongo-Central and Kinshasa provinces respectively between October 2016 and September 2017. A questionnaire was administered to the target population in order to collect relevant data. Plant identification was carried out at the herbarium of University of Kinshasa. The findings revealed that the inventoried medicinal flora is made up of 68 species which are divided into 34 families of 58 genera; the leaf is the most commonly used part in the treatment of diabetes while maceration is the most commonly used method of preparation. The use of medicinal plants is reported in almost all age groups from 20-89 years of age but with a predominance among people aged 40-49 years. Trees and phanerophyte species predominate in the flora studied; the majority of users of these medicinal plants have a primary level of education. In-depth phytochemical and pharmacological studies need to be carried out on these plants with a view to their scientific validation in the diabetes management.


Introduction
Non-communicable diseases represent new challenges for the mankind in the fight for health improvement. Among these diseases, diabetes is a major contributor because it is considered to be one of the four priority non-communicable diseases targeted for intervention by world leaders [1,2]. Diabetes is a serious chronic disease that occurs when the pancreas does not produce enough insulin or when the body is unable to use the insulin produced effectively [3]. However, numerous studies have shown that phytotherapy can be associated with any anti-diabetic treatment and in the case of non-insulino-dependent diabetes, its place may be important as a complement to the diet which has a major role and possible drugs [4]. This is why people are turning to traditional herbal medicine which is less expensive and which they consider as effective as modern therapy. To this end, World Health Organization (WHO) reports that in Africa, more than 80% of the population uses traditional medicine to provide primary health care in both urban and rural areas [5][6][7][8][9][10].
The Democratic Republic of the Congo (DRC) is a reservoir of both faunal and floristic biodiversity [6][7][8][9][10][11][12][13][14][15]. Its flora is full of medicinal plants of biopharmaceutical interest and capable of providing new lead molecules. Thus, ethnopharmacological studies for the scientific validation of these plants are very encouraging, as evidenced by the research results of the last ten years [11][12][13][14][15][16]. The overall objective of this study was to contribute to the knowledge of the plants used in Kinshasa, Central Kongo and Kwango for the management of diabetes. The specific objectives are to conduct an ethnobotanical survey of the population, to identify and give their ecological characteristics (morphological types, biological types, phytogeographic distributions and biotope) and to highlight their therapeutic virtues.

Study Area
The city of Kinshasa is located between 4° 18' and 4° 25' South latitude and between 15° 18' and 4° 22' East longitude. It is bounded to the North and East by Kwango, to the South by Kongo Central and to the West by the Republic of Congo, with an average altitude of 300 m above the sea level. The city is built on the left bank of the Congo River called the Pool Malebo and is crossed by many rivers called allogenic and the three most important are N'djili, N'sele and Mai-Ndombe. The climate of Kinshasa city is of the Aw 4 type, i.e. a tropical climate. It is characterized by a large 8-month rainy season (often interspersed with a small dry period straddling between January and February) and between mid-September and mid-May, and a dry season during the rest of the year precisely between mid-May and mid-September [17,18].
Kwango is located between 6°32'31'' South latitude and 17°2 24'' East longitude, over an area of 89.974 Km 2 with a population of 1.994.036 inhabitants, consisting of Yaka, Suku, Tchokwe, Holo, Lunda Hungana, Mbala, Ngongo tribes. Kwango is divided into five territories namely: Feshi, Kahemba, Kasongo Lunda, Kenge and Popo Kabaka. Kwango is located in a tropical climate zone with two distinct seasons, an 8-month rainy season and a 4-month dry season with a minimum temperature of 20°C and a maximum of 27°C. The vegetation is made up of savannahs, prairies, galleries and forests depending on the territory [19].
Kongo Central is between 4° and 6° south latitude and 12 and 16° East longitude over a 53 920 km 2 area. With a population of 3 615 504 inhabitants, there are the Yombe, Nianga, Ndibu peoples. The population is unevenly distributed in space. Matadi, the chief town of this province, represents 7%, so much so that the Bas Fleuve and Cataractes represent 28% and 36% respectively of the population. Boma 10% and Lukaya 2.3% and the other populations are found in villages and chiefdoms. The climate in Kongo Central is of a tropical Sudanese type climate, subdivided into two types: a first one that extends along the coast, is a steppe type climate with very high variability that lasts for months (from May 15 to September 15) while the other tropical climate that lasts 8 months. Bas-Fleuve is an area where the risk of drought is very high. An ecological niche of Mangrove is observed off the coast. The minimum temperature can be between 15°C and 17°C in the coastal zone and then the maximum at 27°C, in other territories the minimum 20 °C and maximum 27°C [19].

Methodology
An ethnobotanical study was carried out between October 2016 and September 2017 using a survey approach mainly among traditional medicine stakeholders who market their products in different markets of these aforementioned provinces, of which 68 people were interviewed directly using a predefined survey form.
The identification of plants was carried out at the herbarium of the Department of Biology, Faculty of Science, University of Kinshasa by comparison with the available specimens and/or the herbarium of the Jardin Botanique de Kisantu.
At part from the questionnaire used, the ethnobotanical data collected were then supplemented by information on ecological types as follows:

Data Analysis
The data collected in the field were analyzed using SPSS software version 20.0 for descriptive statistics.

Results
The ethnobotanical data and the ecological characters of listed plants are presented in the table below.

Discussion
The different families of listed plants are presented in figure In total, 34 families were listed, and of these families, the Leguminosae has 38.2% of species of this area, followed by Rubiaceae (11.76%), Poaceae, Solanaceae, Malvaceae, Phyllanthaceae, and Lamiaceae (8.82% each) respectively. These results are similar to recent data indicating that Leguminosae is one of the six most represented angiosperms families [20]. From the investigation, it was shown that the leaves are the most commonly used part in the treatment of diabetes. The bark was indicated at the second position (13%) followed by fruit (7%), seed (6%) and root (5%) respectively. At last, it was observed that flower and bulb are the least used. These findings are similar to Ndjouondo et al. [21] who reported that the leaves were the most commonly used part in traditional medicine. On the other side, others researchers reported that the root was much used [10,18].
The different modes of recipes preparation are presented in the figure below. As demonstrated above, three different modes for recipe preparation of medicinal plants were reported. The maceration (63%) was reported as the most commonly used method, followed by the infusion (29%) and decoction (8%). Trees present a higher value (38%), followed by shrubs (24%), annual grass and perennial grass (18% each) knowing that liana species are less represented in this study area. This predominance of trees shows that this ecosystem is more species-diversified than other non-forest ecosystems [10,22].  Thus, their protection should be a concerted effort at the national, sub-regional and regional levels, based on a certain political will. citation (taxa number)
The predominance of phanerophytes among listed taxa is a characteristic of tropical regions and may also correlate with the fact that their tissues have been claimed to synthesize secondary bioactive metabolites [10,[23][24].   This figure shows that the use of medicinal plants is almost universal but concentrated between 40-49 years (32%), followed by the age group 60-69 years. Intakes for the elderly (20-39 years) are the least common.
The elderly are mostly heads of households and represent family authority. Mulwele et al. [25], who inventoried medicinal plants marketed in the various markets of Kwango, reported that 60 out of the 75 respondents were over 40 years of age. These elderly people are also expected to provide more reliable information, as they hold much of the ancestral knowledge that is part of the oral tradition [26]. Anyinam [27] shows that knowledge of the properties and uses of medicinal plants is acquired through a long experience accumulated and transmitted from one generation to the next. Benkhnigue et al. [28] support this view by showing that experience with age is the main source of information at the local level about the use of plants in traditional medicine.
The distribution of respondents according to sex (gender) is presented in the figure below. From the above figure, it was observed that 545% were male and 45% were female. Mulwele et al. [25]    The above figure showed that 72% of medicinal plant users have been enrolled in primary school, 15% have reached secondary school and 3% have reached university level. There were about 10% of people with no education at the school level. These results corroborate with the work of Mulwele et al. [25] and Kahouadji [29] showed that riparian surveyed in Douala have a level of education at least equivalent to that of primary school.

Conclusion
The purpose of this study was to identify the anti-diabetic medicinal plants used in Kinshasa, Kongo Central and Kwango provinces.
The results obtained in this study show that: The inventoried medicinal flora is made up of 68 species which are divided into 34 families of 58 genera; the leaf is the most commonly used part in the treatment of diabetes (65.3%) and maceration is the most commonly used method of preparation; the use of medicinal plants is reported in almost all age groups from 20-89 years of age but with a predominance among people aged 40-49 years; Trees and phanerophyte species predominate in the flora studied; the majority of users of these medicinal plants have a primary level of education.
It would be desirable that in-depth phytochemical and pharmacological studies be carried out on these plants with a view to their scientific validation.