Herbal Medicine: Open Access

Keywords

Ethnopharmacology; Traditional eye medicine; Kigoma district; Tanzania

Introduction

Traditional eye medicines (TEM) are commonly used in different countries. Products used vary from healer to healer and from country to country. Eye problems are many and may be categorized as; (i) Eye infections when pathogenic microorganisms invade any part of the eyeball or surrounding area. The infection may cause redness, pain, discharge, watering and light sensitivity (ii) Eye conditions e.g., cataract, dry eyes and eye allergies and, (iii) Vision impairment e.g., glaucoma, double vision (Diplopia) [1,2].

In Tanzania, like other developing countries the demand for eye care is growing. The dependency on TEM for care and treatment is attributed to several reasons including; few ophthalmologist, inability of medicines purchase and inadequate/distant health facilities to the majority [3]. The drawback of TEM is that, methods and products employed in treatment /management may lead to serious health problems including blindness.

Although TEMs is common in many countries, very few documentation focusing on plants/products used for traditional eye treatment do exist. Our literature search noted a systematic documentation from the study conducted in the Eastern Cape Province, South Africa where 12 plant species medicinal plants belonging to 9 families were documented [4]. Plants used for treatment of eyes diseases/conditions in Tanzania are documented in ethno pharmacological journal articles and books but in a scattered manner while the epidemiological data associated with TEM caused medical problems is scanty. The study was divided in parts namely; Part I dealt with the compilation of previous documented TEMs of Tanzania, Part II concerned with ethno pharmacological survey of TEM in Kigoma District, Part II involved in assessment of knowledge and awareness of health risks associated with TEM and, Part IV covered safety evaluation based on determination of pH and microbial contamination.

Methodology

Literature survey and data compilation

Information on Tanzania medicinal plants for the treatment of eye diseases/conditions was compiled from journal articles and books. Main resources were the publications on the work done by Herdberg et al. [5-7], Chhabra et al. [8-13] and the books of Haerdi [14], Watt and Breyer-brandwijk [15], Kokwaro [16] and Ruffo et al. [17]. Other appropriate Tanzanian published articles are herein cited.

Ethnophamarcological study

Study site: Ethnomedical study was conducted in 9 wards (Bangwe, Buzebazeba, Gungu Kasingilima, Kitongoni, Mwanga Kusini, Mwanga Kasikazini, Machinjioni, Rusimbi) and 6 villages (Ilagala, Simbo, Luiche, Muyobozi, Mwandiga and Sunuka) of the Kigoma district, Tanzania.

Study design: The study followed five steps as outlined below.

Interview: Traditional healers and people who are knowledgeable about medicinal plants were interviewed to obtain traditional products used for treatment of eye problems. The interviews were conducted in their homes guided by the questionnaire (see the attached questionnaire in the annex). Both Kiswahili and vernacular languages were used to obtain reliable information.

Plant material collection, herbaria preparation and identification: In the field, information providers showed the mentioned plants to enable plant materials collection for safety evaluation and herbaria preparation. Identification of the prepared herbaria was done in Botany department, University of Dar Es Salaam.

Awareness on health risks associated with TEM

During the interview information providers tested on awareness of risks associated with the use of TEM based on three selected parameters namely; pain after administration, low vision and blindness.

Safety evaluation

pH determination and microbial detection were carried out in the Pharmacognosy Laboratory and Microbiology and virology Laboratory at the Muhimbili University of Health and Allied sciences using pH meter and following standard microbiology procedures.

pH determination: Preparation of each sample depending on product nature is outlined below. For each tested sample determination was carried out in triplicate, the mean of the obtained values was reported.

Extract preparation: 1 g of plant material from Vernonia amagdalina, Bidens pilosa, Ageratum conyzoides and Commiphora edulis were each macerated with 20 mL of distilled water for 12 hours, filtered to obtain the micelle.

Sap preparation: Leaves of Rumex usambarensis and Solanum lycopersicum were each pounded in the mortar and the sap/ juice squeezed and filtered.

Unrefined salt preparation: A solution of the salt was prepared by dissolving 0.9 g of salt in 100 mL of water.

Palm oil: pH determined using the oil without any dilution.

Determination of microbial contamination: Dry lizard droppings sample was collected from one of the MUHAS offices. The sample was enriched in Brain Heart Infusion Broth, incubated at 37°C for 18 hours. It was then direct cultured on solid media namely; Blood Agar (BA), Chocolate Agar (CA), MacConkey Agar (MCA) and Sabourad Dextrose Agar (SDA) followed by incubation of 48 hours and 72 hours respectively. This was followed on subculturing on similar media and preliminary identification of the microorganisms.

Results

TEM data compiled from previous studies

Data retrieved from journal articles and books gave 65 plant species belonging to 36 families summarized in B. According to this data, proportions of the various plant parts used are presented in Figure 1 and the frequency of mention for the diseases/conditions is presented in Figure 2.

Figure 1 Proportion of plant parts.

Figure 2 Proportions treated diseases.

Ethnopharmacological study in the Manyema Tribe

Recorded TEM: This study was conducted in areas not covered in previous ethnopharmacological surveys done over two decades ago. Recorded products and their corresponding eye disease/ conditions are summarized in Tables 2 and 3.

Table 1: Previous Reported Tanzanian plants used for treatment of eye disease/conditions.

Table 2: Recorded herbal traditional eye medicines used by the Manyema tribe.

Table 3: Recorded non herbal Traditional Eye Medicines used by the Manyema tribe.

Sources and dosage forms of TEM used by the Manyema tribe: Our cstudy afforded to record 19 TEMs where fifteen are of plant origin belonging to 11 families (Table 2) with the frequency of mention for each plant shown in Figure 3.

Figure 3 Frequency of mentioned among recorded plants.

Disease/conditions treated by TEM among the Manyema tribe: Six categories eye diseases/condition treated are as shown in Figure 4.

Figure 4 % Frequency of mention of the treated eye disease/ condition.

Awareness of health risks associated with TEM: Responses from information providers on the four negative health risks of TEM asked are presented in Table 4.

Table 4: Awareness on Risks of Traditional Eye Medicine.

Safety Evaluation

Based on the importance of pH and freeness from microbes in eye medicines, some products were evaluated. pH of tested products were acidic in nature as shown in Table 4. Microbial contamination was observed in the lizard droppings, as presented in Figure 3 and the preliminary identification of microorganisms in Tables 5 and 6.

Table 5: pH of Traditional Eye Medicine Products.

Table 6: Preliminary identification Microbes in the lizard droppings.

Discussion

In previous studies, the use of ambiguous terminologies such as; eye problems, eye diseases, eye trouble, eye ailments, eye ache/pain could not clearly state the disease /condition. This is a drawback if one would wish to conduct scientific research for drug development. Leaves were ranking highest followed by roots. By disregarding the unsorted disease/condition (37%); eye conjunctivitis (33%) was the most treated disease followed by eye infection (12%) (Figures 4 and 5).

Figure 5 Plates showing microbial growth.

Among the recorded TEM in the Manyema tribe, five plants namely; Abrus precatorius, Ageratum conyzoides, Bidens pilosa, Euphorbia hirta and Sesomum angustifolia had previously been reported. Majority of the products (78.9%) were herbal preparation, 15.8% were animal wastes and the unrefined salt as the only mineral product. This is in line with the fact that, botanicals are the main source of traditional medicine. The most used photo-organs are leaves constituting 60%. Product-wise; palm oil was the most frequently mentioned followed by latex of Euphorbia hirta and a solution of unrefined salt. Dosage forms comprised of liquid (juices/saps; 52.6%, latex; 21.1%), and oil; 5.2%) and solid (21.1%) as powders from animal source.

Unlike the data obtained from previous studies, information providers clearly stated the eye disease/condition yielding quality/reliable data for further scientific studies. In part this is due the well-structured questionnaire that gave proper guidance during the interview. Cataract was the most reported among mentioned six eye disease/problem. In part, this could be due to inadequate hospital services or dislike of undergoing surgical operation. It is worth investigating cataract treating TEM as efficacy can easily be assessed by disappearance of the cataract. TEM used for vision improvement is another area of interest for future Confirmation of efficacy, establishment of safety and the mechanism of action(s) for research study.

It should be clear that, we are not advocating the use TEM products reported in this work. However, ethno medical data and little scientific data from literature provide association and conviction on the use of the mentioned plants as TEM as presented below;

Bidens pilosa is used to treat cattle eye keratitis [20]. In vitro studies on extracts of B. pilosa have demonstrated antimicrobial activity against a wide range of bacteria including Klebiseilla pneumonia, Bacillus, Neisseria gonorrhea, Pseudomonas, and Salmonella, Mycobacterium tuberculosis and M. smegmatis [21]. Aqueous leaf extract showed significant anti-yeast activity towards Candida albicans. Polyacetylenes are linked with most of the observed antimicrobial activity and particularly phenylheptatriyne that had shown strong in vitro activity against numerous human and animal viruses, bacteria, fungi and molds in low concentrations [22,23]. Some of these pathogenic microbes are responsible for causing eye infection justifying the antimicrobial use this plant.

Ageratum conyzoides in combination with Dichrocephala integrifolia leaf sap is applied as eyes drops in Tanzania and other African countries [24]. It is also used for treatment of blindness, conjunctivitis and related ocular affections in cattles [25]. Among several antimicrobial testing studies, water and ethanolic extracts had exhibited activity against methicillin-resistant Staphylococcus aureus (MRSA). Phytochemical constituents of A. conzyoide include alkaloids, coumarins, essential oils, tannins various flavonoids including polymethoxylated flavones and polyhydroxyflavones [26]. The plant has limited medicinal applications due toxicity [27].

The use of leaf juice/decoction of Abrus prectorius is reported on for treatment of conjunctivitis and inflamed eyes and seeds infusion against purulent eye infections [7,15]. In cases of cataracts, refractive errors and ocular pain, some healers ask patients to take the seeds of Abrus precatorius orally, and apply root sap into the conjunctival sac [28]. In Africa, powdered seed is added to women's traditional eye makeup in African countries [29]. The methanolic seed extracts showed comparable antibacterial activity to Streptomycin when tested against Enterococcus faecalis, Escherichia coli, Micrococus luteus, Lactobacillus fermentum, Klebsilla pneumonia, Staphylococcus aureus, Streptococcus thermophilus, Streptococcus mitis and Streptococcus mutans [30].

In India, the stem latex of Euphorbia hirta: is used for the treatment of eyelid styes and eye sores. A decoction made from the flowers used against eye infections and inflammations, such as conjunctivitis or pink eye [31]. Various parts of E. hirta had shown various degrees of antibacterial and antifungal activity against Staphylococcus aureus, Micrococcus sp., Bacillus subtilis, Bacillus thuringensis, Escherichia coli, Klebsiella pneumonia, Salmonella typhi, Proteus mirabilis and the yeast Candida albicans [32]. Interesting antiviral activity had been reported and associated with tannins for the high antiretroviral activity [33].

Leaf juice of Kalanchoe lanceolata is reported to treat sore and itching eyes and other Kalanchoe species are used to treat ailments such as infections, rheumatism and inflammation [34]. Ficus natalensis leaf latex is used to treat cataract [35] and for cattle treatment with regard to blindness, conjunctivitis and related ocular affections [25]. Similarly, latex of the related species Ficus thorningii is used as eye drops for eye wound treatment [19].

Palm oil obtained from Elaesis guineensis is rich in natural carotenes as well as tocopherols and tocotrienols that are normally converted into vitamin A in the body when taken orally [36]. The oil is known faster healing of bruises, sunburn and cuts [37]. Since using palm oil as eye drops to improve vision is very popular among the Manyemas tribe, scientific study to confirm its efficacy and mechanism of action(s) is worth undertaking. Swietenia macrophylla is an endangered species but widely used in folk medicine to treat various diseases. It has shown several pharmacological activities inter alia, antimicrobial, anti-inflammatory, antiviral, anticancer and antitumor activities [38].

This work reports the use of Solanum lycopersicum leaf juice for treatment of cataract and visual improvement. In Australia it used for unspecified eye problems [39]. Leaf decoction taken orally is useful in optic nerve and eye weakness [40]. The observed leaf juice pH was 5.3 is too acidic for the application into the eyes. Unpublished data from Mbeya region, Tanzania associate application of leaf juice with blindness in that locality. From the same genus, we report about Solanum tuberosum sap for improvement of the poor vision. This may be linked with the previous report on the potato pulp claimed to reduce the inflammation of the veins that arise under the eyes [41] and is in agreement with the anti-inflammatory effects of potato glycoalkaloids [42]. Despite the mentioned benefits, lack of sterility, is likely to be the source of microbial introduction leading to eye infection.

In the Indian Ayurvedic system of medicine Phyllanthus amarus is used for treatment of various diseases including ophthalmopathy. The extracts and compounds isolated from P. amarus showed a wide spectrum of pharmacological activities including antiviral, antibacterial, anti-inflammatory, antimicrobial etc. [43]. The leaf juice of another reported plant Sesamum angustifolia is use as eye drops and lubricant in Zimbabwe [44]. Besides our report, Rumex usambarensis as eye drops is reported in Africa [45]. In addition for humans application, the fresh leaf juice is used for cattle eye diseases including eye filariosis and malignant tumour [20]. Related species had shown antimicrobial activities e.g., Rumex nepalensis that showed significant antibacterial activity [46] and Rumex cyprius fruits reported to have antiviral activity [47]. Finally, is the plant Vernonia amygdalina whose leaf extract showed antibacterial activity against Staphyloccocus aureus, Bacillus cereus, Escherichia coli, Salmonela typhi, and Shigella dysenteriae [48,49] though not related with cataract treatment as reported herein.

The use of salt solution as TEM is in agreement with the traditional practice where unrefined salt solution is used of washing the eyes and regarded harmless [50] or flushing of eyes with salt solution recommended for treating conjunctivitis caused by viruses or allergies since antibiotics are not useful in such cases [51]. Furthermore, the study conducted in Tanzania among patients at the ophthalmology clinics in Dar es Salaam Tanzania reported 16% of those using TEM employed salt solution [52].

In Tanzania the epidemiological data pertaining to the drawbacks of using TEMs is scanty. A study conducted in Tanzania by Foster and Johnson [53] showed 25% of corneal ulcers associated with the use of traditional eye medicines indicating the magnitude of the problem. In our study pH and microbial contamination were used to assess safety since isotonic with the lacrimal fluid a ophthalmic products are supposed to be isotonic and sterile. Ophthalmic solutions are recommended to have the same pH as the lacrimal fluid (7.4) although pH values ranging 7 to 9 are tolerated by the eye without marked irritation [54]. The pH obtained was ranging from 2.5 to 6.57. Acidic products are not safe to the eyes as they are known to cause considerable redness and burning effects [55].

Python excreta, Lizard droppings are harmful TEM and sources of microbial contamination likely to cause infection. It is unfortunate such product are used as TEM in other countries, they include; a ground cowries, donkey and cow dung, human sputum, bird urine, etc. [50]. Culturing of the lizard droppings revealed contamination with Gram positive and Gram negative bacteria as well as yeast and molds. Applying this product introduces pathogenic microbes that may cause suppurative keratitis, followed by endophthalmitis and panophthalmitis leading to blindness. Keeping in mind that, TEM are commonly used in poor countries with the majority of the patients with AIDS, microbial contaminated TEM products subject them to contract many different fungal infections of the eye [2]. Noted during the interview was lack of sterility in TEM product during preparation and packing/storage and where prolonged use the preparation is required the product is discarded when mold growth is seen with naked eyes. This is another way of contamination TEM with pathogenic microorganisms.

Due to unawareness on the negative health risks associated with TEM traditional healers prefer using substances that cause pain and irritation. The effects are considered as temporary and painful medications in particular being therapeutically effective. TEMs causing pain are likely to bring great damage to both extraocular tissues and/or intraocular tissues of perforated eyes [3]. The reported case from Nigeria where a 39 old man suffered from ocular discomfort and eventually blindness after applying the raw cassava extract in eyes [56] is a good example to disqualify such thinking.

Conclusion

Majority of TEMs reported in this study are from botanical sources. Waste products from animals normally contaminated with pathogenic microbes are also used. 65% among the information providers were unaware of the risks associated with TEMs use. Pain experienced does not worry information providers though ingnoring such complains subject users at higher health risks of eye damage. Sterility which is a vital aspect for ophthalmic products is lacking, tradition healers need to be informed on importance of this aspect. All samples whose pH was determined were acidic in nature; a state that is not safe for the eyes. Since TEM is a common practice in Tanzania and other developing countries, there is a need to educate the public on this situation so as to rescue the users from blindness. On the other hand, scientific studies are essential to identify bioactive compounds and develop safe products.

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