An ethno-medicinal study of medicinal plants used for the treatment of diabetes

Background: Diabetes is the greatest public health problem and is considered as the silent epidemic of the 21st century. In Iran, there are approximately 1.5 million diabetic patients. Before the discovery of insulin, medicinal plants were widely used for the treatment of diabetes in Iran. Objectives: This study aimed to determine the indigenous plants used for the treatment of diabetes in Shiraz, southwest of Iran. Materials and Methods: Semi-structured direct interviews were conducted with 25 herbalists to identify medicinal plants used to treat diabetes. Questionnaires were included herbalist personal information, plant local name, growth season, plant parts used, preparation methods, and traditional therapies. Results: The interview data indicated that, 24 medicinal plants from 19 families are used for the treatment of diabetes in Shiraz. The families with most antidiabetic species were Compositae (13%), Rosaceae (13%) and Cucurbitaceae (8%). The most frequently used plant parts were fruits (38%) and the most common preparation method was decoction (62%). For 45% of reported plants, pharmaceutical studies approved antidiabetic effects in animal or humane model of diabetes. Results of this study showed that the plants recommended by Shirazian herbalists have potential antidiabetic effects. Conclusions: It is suggested that the ingredients of indigenous plants be studied to determine therapeutic effects and mechanism of action. If they were safe and effective, they can be refined and processed to produce natural drugs.

have other conditions such as hypertension, hyperlipidemia, obesity and lower physical activities which greatly contribute to the pathogenesis of cardiovascular diseases. In this regard, it is estimated that in patients with both diabetes and hypertension, the risk of cardiovascular diseases doubles. Diabetic patients often have hyperlipidemia that is mostly associated with premature coronary heart disease. Insulin resistance is also increased in hyperlipidemia. In addition, obesity is associated with insulin resistance and is an important risk factor for heart diseases. More importantly, physical inactivity is another risk factor cardiovascular disease and insulin resistance. Exercising and losing weight have been proved to reduce blood pressure, prevent type 2 diabetes, and reduce the risk of cardiovascular diseases (3). Diabetes type 2 is the most common form of diabetes accounts for about 90%-95% of all diabetes cases. The prevalence of type 2 diabetes has increased dramatically in recent decades worldwide. Type 2 diabetes is a silent disease and many patients are unaware of their situation. As the disease progresses and its complications such as kidney and eye damages appear they become aware of their condition (4)(5)(6)(7). Increased public information about the symptoms, risk factors, prevention strategies and treatment of the disease have been associated with increased level of public health, reducing morbidity and mortality, and improving quality of life for persons (8,9). In Iran, the number of people with diabetes is estimated to be 1.5 million (10). The World Health Organization (WHO) has estimated that the total numbers of patients with diabetes in the world will rise from 135 million in 1995 to 300 million in 2025 (11). Chronic nature of the disease and its complications lead to financial burden and reduction of the quality of life in patients and their family (12). Despite the incurable nature of metastatic cancer, it is believed that a majority of patients can gain adequate control of the disease through self-care activities. Before the discovery of insulin in 1921, diabetes controlling was referred to the prevention of early death from the disease. Todays, diabetes controlling is not only to keep blood glucose, lipid and pressure levels within a normal range, but also to prevent related complication and improve patient satisfaction and quality of life (13,14). People interested in herbal medicines, believe that the use of herbal medicines dates back to the period when there were no modern medicine and no information about the cellular and molecular function of body (15). Although medicinal plants have a long history of use in the treatment of diseases however, their acceptance and application in modern medicine need time (16). However, this alternative medicine is still attractive for people (17)(18)(19). Many common herbs and spices are claimed to have blood glucose lowering effects that make them useful for the treatment of type 2 diabetes. A large number of pharmacological researches on the antidiabetic effects of medicinal plants resulted in an increase in the number of people who use these natural compounds to control their disease (20,21). Before the discovery of insulin and other blood glucose lowering agents, traditional herbal remedies were used to treat diabetes and related complications. To date, more than 1200 medicinal plants have been shown to possess antidiabetic activities (22,23).

Objectives
A wide variety of medicinal plants are used in Shiraz to treat various diseases. This study aimed to determine the native medicinal plants recommended by Shirazian herbalists for the treatment of diabetes.

Materials and Methods
Shiraz is one of the largest cities in Iran and is the capital of Fars province. In 2009, the total population of the city was 1 460 665. Shiraz has a moderate climate and lies in the Zagros mountain range at an altitude of 1468 m. Shiraz city has some famous mountains known as Kuh-e Sabz-Pushan, Kuh-e Bamu, Kuh-e Chel-Magham and Kuh-e Drak. City of Shiraz, with a length of 40 km and a width of 15 to 30 km has a total area of 1268 square kilometers. Shiraz is geographically located in the southwest of Iran and in the central of Fars province. The coldest month of the year is January, with an average temperature of 5°C and the warmest month is July with an average temperature of 30°C. The average annual temperature is about 18°C and the average annual rainfall is 3378 mm.

The methodology of ethno-medicinal data collection
The ethno-medicinal data were collected through direct interview with herbalists and customers between July to September 2015. Herbalists were interviewed in their herbal stores using semi-structured questionnaire and their traditional ethno-medicinal knowledge were recorded. Questionnaires were included herbalist personal information, plant local name, plant growth season, the plant parts used, preparation methods, and traditional therapies. Questionnaires data were transferred to Microsoft Excel.

Ethical issues
1) The research followed the tenets of the Decla-ration of Helsinki; 2) This project was approved by ethics committee of Medical plants Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran.

Statistical analysis
The collected data were processed using Microsoft Excel 2007.

Results
The interview data indicate that 24 species of medicinal plants belonging to 19 families are used for the treatment of diabetes in Shiraz. The families with most antidiabetic species were Compositae (13%), Rosaceae (13%) and Cucurbitaceae (8%). The most frequently used plant parts were fruits (38%) and the most commonly prescribed form was decoction (62%). Ethno-medicinal information of plants used for the treatment of diabetes in Shiraz are shown in Table 1. The number of mentioned anti-diabetic effects for each plant is shown in Table 2. According to the Table  2, species with the highest frequency of mentions in the interview were Juglans regia L, Trigonella monspeliaca L., Urtica dioica and Amygdalus scoparia Spach. The percentage of botanical family used, the used parts and preparation method are shown in Figures 1-3.

Discussion
Diabetes is the seventh leading cause of death, affecting more than 100 million people each year (5). It has been estimated that the total numbers of patients with diabetes in the world will rise from 150 million in 2003 to 300 million in 2025 (6). The use of medicinal plants is the main component of alternative and complementary medicine (7,8).   Their effective compounds and mechanism of action are also suggested to be determined. In the case  of effectiveness, these plants can be processed and refined to produce drugs The mechanisms by which these plants lower blood glucose are not clear. Although, it has been shown that various herbal components such as phenolics, tannins, saponins and alkaloids have antidiabetic properties, flavonoids and phenolic components are characterized as the main blood glucose lowering components (32)(33)(34)(35). If we accept this hypothesis, thus, other medicinal plants with phenolic and antioxidant compounds may possess anti diabetic property. Furthermore, considering the importance of these plants in reducing blood glucose, more investigations are recommended to scientifically confirm the effects of these plants. Following the confirmation of the effects, more researches are also needed to analyze the effective compounds and to introduce new hypoglycemic drugs.

Conclusions
This study introduced important plants species which were recommended by local herbalist of Shiraz for the treatment of diabetes. A total number of 24 plants are recommended for the treatment of diabetes. For 45% of reported plants, pharmaceutical studies approved antidiabetic effects in animal or humane model of diabetes. The most frequently used part was fruits and the most commonly used preparation methods was decoction.