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Folk medicinal practitioners form the first tier of primary health-care providers to most of the rural population of Bangladesh. They are known locally as Kavirajes and rely almost solely on oral or topical administration of whole plants or plant parts for treatment of various ailments. Also about 2% of the total population of Bangladesh are scattered among more than twenty tribes residing within the country's borders. The various tribes have their own tribal practitioners, who use medicinal plants for treatment of diseases. The objective of the present survey was to conduct an ethnomedicinal survey among the Kavirajes and tribal practitioners to determine which species of plants belonging to the Verbenaceae family are used by the practitioners. The Verbenaceae family plants are well known for constituents having important bio-active properties. The present survey indicated that 13 species belonging to 8 genera are used by the folk and tribal medicinal practitioners of Bangladesh. A comparison of their folk medicinal uses along with published reports in the scientific literature suggests that the Verbenaceae family plants used in Bangladesh can potentially be important sources of lead compounds or novel drugs for treatment of difficult to cure debilitating diseases like malaria and rheumatoid arthritis.
The Verbenaceae family of plants, which is also commonly known as the verbena or vervain family consists of trees, shrubs and herbs. They are mainly flowering plants found in the tropical regions of the world. The family includes some 35 genera and around 1,200 species.
The Verbenaceae family plants are well known for their uses in the traditional medicinal systems of various countries. Quite a number of the plants have been reported to contain bio-active phytochemicals with important pharmacological effects. To cite only a few recent publications, abietane diterpenoids having anti-microbial and anti-parasitic (anti-leishmanial, anti-malarial) properties have been isolated from the roots of Clerodendrum eriophyllum Gürke (Machumi et al., 2010). Ethanolic extract of Premna corymbosa (Burm.f.) Rottl. & Willd. leaves reportedly suppressed the development of chronic arthritis in rats induced by Complete Freund's Adjuvant (Karthikeyan and Deepa, 2010).
Essential oil obtained from leaves of Lippia gracilis Schauer reportedly possessed antinociceptive and anti-inflammatory activities. Notably the plant is used by folk medicine practitioners of the Caatinga region of Northeastern Brazil for these properties (Mendes et al., 2010). Essential oil obtained from Lippia graveolens Kunth reportedly inhibited the growth of Giardia lamblia, the causative agent for the diarrheal disease, giardiasis (Machado et al., 2010). Anti-oxidant and cytotoxic activity of essential oil from leaves and fine stems of Lippia schomburgkiana Schauer (main constituents 1,8-cineole and α-terpineol) has been demonstrated (da Silva et al., 2009). Essential oils obtained from Lippia turbinata Griseb. and Lippia polystachya Griseb. reportedly demonstrated lethal effects against mosquito larvae of Culex quinquefasciatus, where ambulation speed and total time of ambulation was significantly decreased (Kembro et al., 2009). Essential oil of Lippia sidoides Cham. has been shown to have anthelmintic activity against sheep gastrointestinal nematodes (Camurça-Vasconcelos et al., 2007; Camurça-Vasconcelos et al., 2008). Anti-spasmodic activity has been reported for essential oil from Lippia dulcis Trev., a plant used in traditional medicine of Central America for cough, colds, bronchitis, asthma, and colic (Görnemann et al., 2008).
A new anthraquinone, named tectone (3,8-dihydroxy-2-methyl anthraquinone) with anti-hyperglycemic properties has been isolated from leaves of Tectona grandis L.f. (Shukla et al., 2010). Essential oils obtained by hydrodistillation of Aloysia polystachya (Griseb.) Moldenke and Aloysia citriodora Ortega ex. Pers. have been reported to have ovicidal activity against eggs and second instar nymphs of the soybean pest Nezara viridula (Hemiptera: Pentatomidae). The major components in the oil were carvone for A. polystachya, and citronellal and sabinene for A. citriodora (Werdin González et al., 2010). Pro-apoptotic activity of essential oil from Verbena officinalis L., and its main component citral has been reported in experiments conducted with lymphocytes collected from patients with chronic lymphocytic leukemia (De Martino et al., 2009). Anti-oxidant and anti-fungal properties have been shown of various solvent extracts of leaves of V. officinalis (Casanova et al., 2008).
Ethanol extract of Stachytarpheta jamaicensis (L.) Vahl reportedly demonstrated anti-inflammatory properties in animal models of nociception and inflammation (Sulaiman et al., 2009). Anti-inflammatory phenylpropanoid glycosides have been reported from leaves of Clerodendron trichotomum Thunberg (Kim et al., 2009). The plant, Clerodendrum umbellatum Poir is used in the traditional medicinal system of Cameroon for treatment of intestinal helminthiasis; aqueous extract of leaves have been shown to demonstrate schistosomicidal properties in Schistosoma mansoni mice model (Jatsa et al., 2009). Another plant, Acantholippia deserticola (Phil.) Moldenke, used in traditional northern Chilean medicine, has been shown to have anti-oxidant properties (Morales et al., 2008).
Bangladesh has a rich tradition of alternative medicinal practices, which include homeopathy, Ayurvedic, Unani, and folk medicine. The latter is practiced by folk medicinal practitioners known commonly as Kavirajes, who rely almost exclusively on medicinal plants for treatment of various ailments. The mode of plant usage is simple, being decoctions, pastes or macerations of whole plant or plant parts followed by topical or oral administration. The Kavirajes tend to keep the knowledge within the family and which is passed from generation to generation. As a result, the Kavirajes over hundreds of years have accumulated considerable knowledge on medicinal plants of Bangladesh. Almost every Kaviraj has his unique repertoire of medicinal plants, and as such, the use of medicinal plants for treatment of a given ailment may differ between Kavirajes of even adjoining villages. Villages form the primary unit of human habitation in the country and almost every village has one or two practicing Kavirajes, who in turn form the primary health-care providers to the inhabitants. This is more so because the villagers not only lack modern medicinal facilities but also most of the time, they cannot afford the price of modern allopathic drugs. Moreover, since the Kavirajes reside within the village, the rural people feel more comfortable to discuss with the Kavirajes their health problems.
About 2% of the population of Bangladesh are scattered among more than twenty tribes within the country. The tribal medicinal practitioners also rely on medicinal plants for treatment of various diseases. Even as of this date, the tribal people obtain primary health-care from their own practitioners instead of visiting allopathic doctors, who are in reality absent from most of the tribal villages.
We had been conducting ethnomedicinal surveys in numerous villages and among various tribes of Bangladesh over the last few years (Hossan et al., 2010; Mollik et al., 2010; Rahman et al., 2010; Rahmatullah et al., 2010 a–i). In our ethnomedicinal surveys we noticed that Verbenaceae family plants hold considerable importance with the Kavirajes for treatment of a considerable number of ailments. The objective of this review is to describe the use of Verbenaceae family plants by the Kavirajes and tribal practitioners of Bangladesh.
The population of Bangladesh is quite homogenous with about 98% of the people speaking the Bengali language. The majority of the population resides in the 86,000 villages and small towns of the country. The number of large cities is only four with only two cities, namely Dhaka and Chittagong, which can be considered as major cities with modern health care facilities and a sizeable number of allopathic doctors. About 2% of the total population are scattered among the various tribal populations of the country, who reside mainly in the south-eastern, north-eastern, and northern regions of the country. Ethnomedicinal surveys were conducted among the Kavirajes, randomly selected from various villages of the 64 districts of Bangladesh. Surveys were further conducted among the major and some minor tribes of the country, which included the Garos, Santals, Manipuris, Chakmas, Marmas, Chaks, Tonchongas, Rakhains, Murongs, Tripuras, and the Khasias.
All surveys were conducted with the help of a semi-structured questionnaire and the guided field-walk method as described by Martin (1995) and Maundu (1995). Briefly, informed consent was first obtained from the Kavirajes and tribal medicinal practitioners. The objective of the survey was explained and consent obtained that the results may be disseminated nationally and internationally. Where tribes were concerned, actual surveys were conducted through an interpreter, who usually happened to be the Headman of the tribe and conversant in both the tribal language as well as Bengali. Kavirajes took the interviewers in field-walks to places from where they collected their medicinal plants, pointed out the plants and described their uses. All plant specimens were collected on the spot, dried and later brought back to the Bangladesh National Herbarium at Dhaka for proper identification. Occasionally, we relied on Mr. Manzurul Kadir Mia, ex-Principal Scientific Officer and Curator of the Bangladesh National Herbarium for plant identification. Information obtained from the Kavirajes and tribal medicinal practitioners during daytime field-walks were cross-checked in evening meetings with the practitioners and any other interested person of the village present at those meetings.
The various surveys conducted among Kavirajes and different tribes of Bangladesh indicated that altogether 13 species distributed into 8 genera of Verbenaceae family plants are used by the folk medicinal and tribal medicinal practitioners within the country. Four plants belonged to the Clerodendrum genus, while two plants belonged to the Lippia genus. From the number of ailments treated and citations by the Kavirajes, Clerodendrum viscosum was the most frequently used plant followed by Clerodendrum indicum and Nyctanthes arbor tristis. Rheumatoid arthritis and skin diseases appeared to be the ailments for which the Clerodendrum genus was used for treatment. The results are summarized in Table 1.
The various plant parts used for treatment included whole plants, leaves, roots, stems, barks, meristems, flowers, fruits, and seeds. Of the various plant parts used, leaves constituted the majority of uses (26.7% of total uses), followed by whole plants (15.6%), roots and stems (13.3% each), barks and flowers (11.1% each), fruits (4.4%), seeds and meristems (2.2%). Whole plant, individual plant parts, as well as a combination of plant parts were observed to be used for treatment of various ailments. For instance, whole plants of Clerodendrum indicum were used for treatment of coughs, rheumatoid arthritis, jaundice, skin diseases, edema, cancer, diabetes, and boils, while leaves were used for treatment of skin lesions on children's throat, to remove scars from face and body, skin rash, whooping cough, allergy, and abscesses. The stems of the same plant were used for treatment of eczema, itches, and toothache. A combination of leaves and roots was used for treatment of diseases of the fetus, while a combination of leaves and bark was used for treatment of skin disorders.
Although only 13 Verbenaceae family plants were used by the folk medicinal practitioners, a wide variety of diseases were treated. Among the most frequent diseases treated were skin diseases, gastrointestinal disorders, respiratory tract disorders, rheumatoid arthritis, fever, hepatic disorders like jaundice, sexually transmitted diseases, malaria, helminthiasis, and nerve disorders. Other diseases treated with Verbenaceae family plants included heart problems, cancer, edema, measles, allergy, pain, tuberculosis, menstrual problems, herpes, night blindness, sexual disorders, hypertension, cuts and wounds, fracture or sprain, snake bite, scorpion bite, dog bite, rheumatic fever, dengue fever, head lice, nausea, vomiting, urinary tract problems, leukorrhea, hepatitis, fistula, and tetanus. Of the 13 Verbenaceae family plants used, 8 plants were used to treat skin diseases, 7 plants for treatment of gastrointestinal disorders, and 5 plants each for treatment of respiratory tract infections, rheumatoid arthritis, fever, and malaria. A plant may be used for treatment of both human and cattle diseases, e.g. Clerodendrum viscosum, which while used for treatment of various human ailments was also used for treatment of colic in cattle.
Regarding tribal usage, Clerodendrum viscosum was the most frequently used plant by various tribes, including the Chak, Garo, Manipuri, Marma, Santal, and Tripura tribes. The plant next most frequently used by various tribes was Clerodendrum indicum, which was used by the Garo, Rakhain, and Tripura tribes. The ailment(s) treated by any tribe with a particular plant was not necessarily the same as other tribes or the Kavirajes belonging to the mainstream population. To cite just one example, Clerodendrum indicum was used by the Garo tribe for skin rashes, but used by the Rakhain tribe for eczema, itches, and toothache. While it may be argued that skin rashes, itches and eczema are all skin disorders, nevertheless the use of the plant for treatment of toothache was unique to the Rakhain tribe. The Rakhain tribe also used the plant for treatment of gastrointestinal problems, respiratory problems like coughs and asthma, as well as swellings in any portion of the body. Notably the mainstream Kavirajes used the same plant or plant parts for treatment of ailments like cold, asthma, respiratory problems, bloating, tuberculosis, diseases of the fetus, excessive menstrual bleeding, sexually transmitted diseases, skin and soft tissue infections, edema, and rheumatoid arthritis. Thus while a common feature may be noted in the treatment by various tribal practitioners and Kavirajes in the treatment of skin-related disorders, overall there were more varieties in diseases treated than common uses of the plant. Duranta repens was another plant used for treatment of malaria by tribal practitioners as well as mainstream Kavirajes. But while the Garo tribal medicinal practitioners used the plant exclusively for treatment of malarial fever, mainstream Kavirajes utilized the plant as an insect repellent, and for the treatment of itches, infertility, fever, and pneumonia besides treatment of malaria.
A number of the Verbenaceae family plants have reported bio-active properties, which validate their use in the folk medicinal system of Bangladesh. Clerodendrum inerme has been reported to have significant antinociceptive activity (Parveen et al., 2010), which might explain its use for rheumatoid arthritis, which has quite intensive pain as one of its symptoms. Anti-inflammatory properties has also been reported for Clerodendrum trichotomum (Kim et al., 2009), which again can justify its folk medicinal use in Bangladesh for treatment of rheumatoid arthritis. The plant, Lippia nodiflora also reportedly has anti-inflammatory and antinociceptive effects (Ahmed et al., 2004), which can be useful in the treatment of rheumatoid arthritis for which purpose the plant is used locally.
Mosquitocidal triterpenes as well as anti-plasmodial activity have been reported for Duranta repens (Nikkon et al., 2010; Ijaz et al., 2010), justifying its use as insect repellent and for treatment of malarial fever in Bangladesh. Oleanolic acid has been isolated from Lantana camara, a compound reported to have anti-plasmodial properties (Moon et al., 2007). Notably the plant is used as an anti-malarial by folk medicinal practitioners of Bangladesh. The essential oil of the plant also reportedly has anti-bacterial properties (Kurade et al., 2010), which can justify its local use for coughs, and anti-mycobacterial properties (Kirimuhuzya et al., 2009) justifying its use for treatment of tuberculosis.
Nyctanthes arbor tristis is used in Bangladesh for treatment of fever, bacterial infections, and rheumatism as well as other ailments. Validation of the plant's use can be found in the scientific literature, which describes anti-pyretic and analgesic effects of the plant (Saxena et al., 1987), as well as anti-bacterial properties of its flowers (Khatune et al., 2001).
Overall, the Verbenaceae family plants used in Bangladesh appear to have constituents with pharmacological properties, which can be useful in the treatment of bacterial and fungal infections, malaria, and pain arising from various causes including rheumatoid arthritis. The plants merit detailed studies which can prove useful in the discovery of lead compounds leading to novel and more efficacious drugs. The importance of the plants used in Bangladesh lies more so in their potential for treatment of malaria and rheumatoid arthritis, two of the most debilitating diseases affecting millions of people throughout the world.