Antiasthmatic Medicinal Plants of Tanzania: An Ethnomedicinal and Ethnopharmacological Review

Traditional medicinal plants (TMPs) are a significant part of people's quality of life, offering a natural substitute for modern drugs with numerous side effects. In Tanzania, data on antiasthmatic TMPs are highly fragmented. This review, a comprehensive compilation of ethnobotanical research evidence, aimed to provide a thorough understanding of TMPs used by the locals for asthma management and identify species that have already been investigated in preclinical studies. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. To gather relevant literature on antiasthmatic TMPs used by Tanzanians, a web search using electronic databases (Scopus, PubMed, ProQuest, Academic Library, Web of Science, SciFinder, Wiley Online Library, Google Scholar, ScienceDirect, and African Journals Online) was conducted. The scientific names were verified through the Plants of the World Online database, and the collected information was analysed for descriptive statistics using Microsoft Excel software. The ethnomedicinal information was obtained from 24 different articles. Microsoft Excel software was used to analyse the data using descriptive statistics. A total of 62 TMPs belonging to 33 families were identified. Species of the Fabaceae (14.5%) and Rubiaceae families (8.1%) are the most utilized. The analysis revealed that trees (42.0%) and leaves (40.0%) are the most utilized life forms and plant parts, respectively. Most plant materials (59.7%) used to make remedies were collected from the wild environment. Decoction (55.0%) is the dominant preparation method of remedies, and the majority (69.0%) were orally administered. Of the recorded TMPs, 22.6% had their in vivo antiasthmatic activity reported in the literature. The review also highlighted the strategic significance of preparations of remedies made from TMPs for discovering and developing new antiasthmatic drugs. However, the need to identify the molecular targets of action and toxicological aspects of the TMPs should be considered.


Introduction
Asthma is a life-threatening respiratory disorder afecting people of all ages worldwide.Te disorder is caused by infammation and muscle constriction around the airways, resulting in clinical symptoms such as chest tightness/pain, breathing difculties, triggering coughing, a whistling sound (wheezing) when exhaling, and shortness of breath [1,2].Over the past decades, the prevalence of the disorder has increased progressively, and it is estimated that more than 100 million people may be afected by 2025 [3].According to the World Health Organization (WHO), about 455,000 deaths worldwide were recorded in 2017 to be caused by asthma.Te disorder remains the most frequent noncommunicable disease (NCD) in children and adolescents in most African countries.With NCDs set to surpass infectious diseases in the continent by 2030, eforts to address asthma are required.Despite this, asthma often remains undiagnosed and is associated with considerable morbidity and mortality.Also, environmental exposure, stigma, and poverty worsen outcomes for a population with asthma [4].Te prevalence of asthma in developing and developed countries varies greatly from less than 5% to about 20%, respectively [5].Te pervasiveness of the disease has been growing over the past decades, with the highest increase seen among children and young adults.In Tanzania, the prevalence of the disease condition, such as wheezing, is reported to be between 12.1% and 23.1%, while that of exercise-induced asthma is between 2.4% and 26.3%.On the other hand, self-reported asthma is between 6.4% and 17.6% [6].
Traditional medicinal plants (TMPs) are a perpetual and treasured source of novel bioactive agents.TMPs' secondary metabolites, such as favonoids and phenolic compounds like apigenin, quercetin, kaempferol, rutin, mangiferin, and luteolin, have been investigated and found to prevent and treat respiratory disorders, including asthma [7][8][9][10][11].Nevertheless, despite the pharmacological and therapeutic potential of compounds of TMP origin, documentation of medicinal plants in Tanzania has not been adequately done, and registration of patents has declined in the last decades.Tus, such circumstances are worrisome and divulge the need for actions to increase the research on natural products, especially given Tanzania's rich biological diversity of plants [12,13].Te locals in Tanzania have been using diverse TMPs such as Mangifera indica L. [14,15], Ocimum basilicum L. [16], Leonotis nepetifolia (L.) R.Br.[17,18], Balanites aegyptiaca (L.) Delile [19,20], and many others to treat asthma.Tese TMPs can be considered important sources of bioactive compounds that can be used in the formulation of novel drugs for asthma management.
It is apparent that TMPs signifcantly enhance people's health and quality of life and that Tanzanian biodiversity is vital in the search for new bioactive ingredients with promising efects against asthma.Tus, the present review aims to ofer a comprehensive list of the scientifc records on TMPs used to manage asthma in Tanzania and identify the TMPs already studied in preclinical and clinical assays.Tis review is the frst in the country to bring together all the records in the literature on the TMPs of Tanzania fora used to manage asthma.

Literature Search Strategy.
Tis comprehensive review has gathered data on antiasthmatic TMPs used by Tanzanian communities.Te review was accompanied by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement (Figure 1) [21].Scopus, Medline (PubMed), ProQuest, Academic Library, Web of Science, SciFinder, Wiley Online Library, Google Scholar, Science-Direct, African Journals Online, and OpenGrey were systematically searched for relevant published peer-reviewed articles, books, and reports related to antiasthmatic TMPs.Te following keywords: "traditional medicinal plants," "herbal/traditional remedies/medicines/therapies," "ethnobotany," "ethnomedicine," "ethnopharmacology," "medicinal plant," and "phytomedicine," were searched in combination with keywords regarding "asthma," "antiasthma," "anti-asthmatic," "United Republic of Tanzania," and "Tanzania."Te accuracy of the identifed TMPs' scientifc names was verifed through the Plants of the World Online (https://powo.science.kew.org/)botanical database.Also, each recorded TMP was searched using the same databases to obtain information on their antiasthmatic potential and safety.Tus, all articles reporting antiasthmatic activities and the safety of the TMPs were surveyed, and their fndings were summarized.Ethnomedicinal uses of the recorded TMPs in other African countries were recorded, too.

Eligibility Criteria.
All peer-reviewed articles, book chapters, conference publications, and books presented in the English language were included.Still, oral presentations, review articles, hypotheses, letters, nonretrievable articles, articles with limited TMPs data, and those not well designed were excluded.Moreover, all studies that had diferent attributes such as family name, local plant name, habitat, life form, plant part used, preparation mode, and application route were included in the study.

Ethnomedicinal Data Analysis.
Te collected ethnomedicinal information was entered into the Microsoft Excel software and analysed for descriptive statistics of the recorded botanical families, TMPs, plant parts used, life forms, methods of preparation, routes of application, and associated indigenous knowledge.Te fndings were then presented as tables and fgures.

Results and Discussion
3.1.Literature Search.A total of 249 potential studies were included in the database.Te exclusion of duplicates led to the initial screening of 94 articles based on their titles and abstracts.After initial screening, 46 articles were eliminated, and 48 were subjected to screening based on retrievability, where six articles were excluded as they were not retrievable.Ten, the 42 retrievable articles were screened for eligibility, and only 24 studies were included in this systematic review.Figure 1 displays the PRISMA fowchart and selection process for the review.

Distribution of Antiasthmatic Traditional Medicinal
Plants.Tis review has recorded 24 ethnobotanical studies presenting TMPs from 14 regions out of 31 administrative regions of Tanzania (Figure 2).Te fndings indicate that research on the prevalence of asthma in Tanzania is limited.Te majority of the recorded antiasthmatic TMPs were reported in the Pwani Region (37.8%), followed by the Tanga Region (30.6%),Dar es Salaam (22.6%),Morogoro (19.4%),Kilimanjaro (14.5%), and Tabora (9.7%).Arusha (3.2%), Mtwara, Mara, and Iringa (1.6% each) regions had fewer antiasthmatic plants (Figure 2).Te high number of reported antiasthmatic TMPs in the Pwani, Tanga, and Dar es Salaam regions indicates that the locals in the regions have good aboriginal knowledge on using TMPs against asthma, and possibly these regions have many asthmatic incidences.

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Te Scientifc World Journal Euphorbiaceae, Lamiaceae, and Rutaceae (4 species, 6.5% each), and Anacardiaceae and Capparaceae (3 species, 4.8% each) families (Table 1).Te predominant use of these families for treating asthma and related complications is attributed to possessing a widespread range of bioactive ingredients, making them primarily efective in managing human ailments [31,67].As in many African countries, the general use of TMPs for treating asthma and other ailments among Tanzanians is due to their afordability, cultural acceptability, ease of access, and fewer side efects [71][72][73].Tis suggests that TMPs are vital alternatives to the presently accessible conventional asthma remedies, especially for low-income families.Similar to this study's fndings, other ethnobotanical studies conducted in Brazil [31], India [74], South Africa [22], Togo [23], and Rwanda [32] have also reported the dominant use of antiasthmatic TMPs belonging to Fabaceae.Euphorbiaceae [24], Rutaceae [32], and Lamiaceae [75] are extensively used to treat several allergic infammatory conditions, including asthma.Additionally, the prevalent and high utilization of TMPs from these botanical families indicates that they are broadly distributed all over the globe.
3.4.Plant Life Forms, Habitats, and Parts Used.Medicinal plants identifed in this review were mainly trees (43.6%), followed by shrubs (30.6%) and herbs (25.8%).Tis observation, however, is not surprising since these life forms are dominant components of local fora across the country.Te more familiar the TMPs' life form is in an area, the greater the likelihood of its prevalent utilization is [22,76].Terefore, the locals in Tanzania might wish for the aforesaid life forms due to their abundance, ease of accessibility, and familiarity.Most collected TMP resources were from the wild environments (59.7%), followed by wild and cultivated environments such as farms and home gardens (21.0%) and cultivated areas (19.3%).A similar fnding was reported in Ethiopia [77,78], Cameroon [79], and South Africa [80], whereby most herbal medications were collected from wild.Te dependency on wild resources is because they are free, as no licences are obligatory for collection.TMP users consider cultivated plant resources less efective than wild ones [42].Hence, conserving and protecting wild environments is paramount for ensuring a sustainable supply of TMPs.
Moreover, the study suggests the need to adopt both macro Te Scientifc World Journal and micropropagation strategies as a conservation strategy and an excellent means of reducing the exploitation pressure on wild resources.Te strategy will ensure future access to the remedies of TMPs and provide a sustainable supply of raw materials for developing afordable modern drugs through up-to-date science.
It was observed that leaf (40%) was the most preferred plant part for antiasthmatic remedy preparation, followed by root (36%), bark (18%), fower (3%), whole plant (2%), and fruit (1%) (Figure 3).Te high use of leaves compared to other TMPs parts might be due to their efectiveness, which is related to a higher accumulation of bioactive ingredients with therapeutic potential, ease of harvest, and swift ability to regenerate [81].Te TMP leaves are also known for synthesising most secondary metabolites that are benefcial in therapeutic activities [82].Te widespread use of leaves for asthma management corroborates with the fndings reported in Brazil [31] and Togo [23], which also reported the highest use of leaves for asthma treatment than other plant parts.In contrast to this study's fnding, the root was reported to be commonly used to treat asthma and related conditions in South Africa [22].Despite being rich in bioactive compounds, the frequent harvest of roots can endanger the survival of TMPs [82].Terefore, the use of leaves is highly encouraged if they can be used to serve the same purpose.Appropriate harvesting tactics and conservation strategies are crucial for safeguarding the sustainable utilization of TMPs resources.

Preparation and Administration
. Decoction (56%) and infusion (25%) were the most common methods of preparing antiasthmatic remedies.Other methods include powdering, ashing, and concoction (Figure 4).Decoctions involve boiling collected TMPs materials in a specifc quantity of water and allowing the mixtures to cool before administration.In contrast, infusion involves pouring hot or warm water onto the plant material and allowing the mixture to cool before administration.Te high preferential use of decoction in preparing remedies is due to its simplicity of preparations, and it helps the extraction of bioactive compounds and preservation of the herbal remedies longer than cold water [83].Moreover, the decocts are swiftly absorbed and have considerable actions in all   Te Scientifc World Journal [14] South Africa [22], Togo [23], Nigeria [24,25] Amaranthaceae Chenopodium ambrosioides L. Morocco [27], Bolivia [28] Anacardiaceae Lannea schweinfurthii var.stuhlmannii (Engl.) Decoction drunk [15] Kenya [29], Mozambique [30] Mangifera indica L.

Similar Traditional Use of Medicinal Plants Elsewhere.
Moreover, the review has revealed that 59.7% of the recorded TMPs are similarly used for asthma management in other parts of the world (Table 1 [22], Harrisonia abyssinica Oliv.(Rutaceae), A. precatorius in Kenya [51], W. somnifera in Ethiopia [67], and Dysphania ambrosioides (L.) Mosyakin and Clemants in Bolivia [28] and Morocco [27].Te wide utilization of TMPs by diferent ethnic groups from other countries indicates that TMPs possess potential antiasthmatic bioactive ingredients that can be used to develop afordable modern drugs.

In Vivo Antiasthmatic Activities of Some Medicinal Plants
Reported in Tanzania.Out of the total recorded TMPs in this study, only 22.6% (14 TMPs) have been examined for their antiasthmatic potential through preclinical investigations using experimental animal models (Table 2).Te dominant animal models used were mice, guinea pigs, and Wistar rats.Te pharmacological potential of the TMPs was assessed using extracts, essential oil, fractions collected from the extracts, and isolated compounds.Te ovalbumininduced (OVA-sensitized) asthma model was the most preferred one for evaluating the pharmacological efect of the products obtained from TMPs.Te reported information on in vivo antiasthmatic activities of the TMPs (Table 2) is of great signifcance in supporting or refuting the indications of the use of the recorded TMPs in traditional medicine.For instance, fresh seeds of O. basilicum were found to have immunomodulatory and anti-infammatory efects and tended to lessen mucus hypersecretion in mice's OVA-induced allergic asthma model [104,107].Te ethanol extract of A. precatorius leaves at doses of 100, 125, and 150 mg/kg was evaluated and revealed to inhibit clonidineinduced catalepsy signifcantly and possess antihistaminic activity [90].Moreover, the n-butanolic fraction (NBF) of the fruit pulp of Balanites aegyptiaca (L.) Delile showed a dose-dependent (at 50, 100, and 200 mg/kg p.o.) benefcial efect on the degranulation rate of actively and passively sensitized mesenteric mast cells of albino rats when challenged with antigen (horse serum).Also, the NBF fraction signifcantly reduced the serum IgE level and number of eosinophil cell count in rats, showed signifcant antihistaminic activity in histamine-induced contraction in goat tracheal chain preparation, and resulted in substantial protection against acetylcholine and histamine aerosolinduced bronchospasm in guinea pigs [70].Among the recorded TMPs used for asthma management in this review, only two, Mangifera indica L. and M. paradisiaca, have had their antiasthmatic potential investigated through randomized clinical trials.Te species revealed relevant antiasthmatic activity, and their products can be used as an efective alternative to complementary therapy for asthma.Tese results are essential to validate the indications of Tanzanian communities' traditional use of these plants [31].On the other hand, the clinical trials of the pseudostem powder capsules of M. paradisiaca showed no therapeutic efects when administered to asthmatic patients [108], while Acalypha fruticosa Forssk possesses powerful bronchodilatory, anti-infammatory, antihistaminic, Te Scientifc World Journal

Leaves Ethanol extract 100 µg/ml
His-induced Goat tracheal chain, mice, rats [91] Allium sativum L. 10 Te Scientifc World Journal antiallergic, and mast cell stabilizing activities [91].Tese plants proved to be efcient antiasthmatic agents and, hence, can be used to discover modern drugs.
3.8.Future Research and Perspectives.Tis review disclosed that locals in Tanzania rely on TMPs to treat various human ailments, including asthma, and are well informed about their identities and use of the TMPs.Data collected in this review demonstrate that asthma is treated with a good number of TMPs.Te present fndings correlate with ethnobotanical studies conducted in various parts of Africa, such as South Africa [22], Togo [23], and Nigeria [24], as well as those conducted elsewhere in the world, such as in India [74] and Brazil [23], that asthma is a life-threatening disorder globally.Reports of comparable therapeutic applications of the documented TMPs in Africa and the rest of the world (Table 1) show that these TMPs are treasured sources of ethnomedicines.Te comparative analysis reinforces the frm belief that indigenous knowledge represents an important heritage developed over the centuries and a considerable mass of data that should be exploited to provide new and valuable knowledge on plant resources.Terefore, it is essential to preserve this knowledge through proper documentation, plant species identifcation, herbal preparation, and dosage.
Te present review will help future research on the choice of TMPs to investigate phytochemical safety and pharmaceutical efcacy.Furthermore, there is a need for more research on the bioactive compounds of these TMPs, some of which have already revealed antiasthmatic activities, as shown in Table 2. Also, the study suggests a need to establish the linkage between the bioactivity and specifc compounds responsible for the extensive use of these TMPs.Te documented indigenous knowledge in Tanzania and available scientifc literature sturdily suggest that at least some of the TMPs used as medications can be potential sources of new contemporary drugs.Currently, phytochemical and pharmacological analysis of TMPs is vital in medicinal plant research and indigenous knowledge systems.Tus, sharing such knowledge is central to maintaining possibilities for using TMPs, particularly as alternative herbal medicine is mounting because of its low costs and increasing belief in herbal remedies.Worldwide, knowledge of orthodox pharmaceuticals has originated from traditional indigenous knowledge.For instance, many of the conventional drugs traded in today's market have a long history of applications as traditional medications; among them are quinine, opium, and aspirin.While Tanzania is gifted with a robust culture of traditional medicine usage for primary healthcare, there is a need to normalize the preparation methods, dosage, and route of administration.Validating the relationships of the ethnomedicinal uses, bioactive compounds, and biological and pharmacological efects is highly signifcant and is still a primary task for future investigations.Moreover, eforts are required to explore the physiological and biochemical activities demonstrated by the recorded TMPs, and identifcation of the bioactive ingredients and their associated mechanisms of action is paramount.
Like many other African countries, Tanzania is an imperative repository of TMP applications in primary healthcare.Tis is echoed in the variety of TMPs used for therapeutic purposes in various regions in the country and the extensive range of their usages and associated indigenous medicine procedures [12-20, 76, 86].Te country's demand for traditional medicines to cure various human ailments has increased enormously.As the market continues to accelerate, awareness should be created among local communities to ensure sustainable use and conservation of the TMPs.A collaborative approach to sustainable use, conservation, and management of TMPs should be implemented, and all stakeholders should be involved.Communities in Tanzania should be actively engaged in managing plant resources as they rely on them for their primary healthcare needs.Hopefully, this will balance meeting their health needs and wise utilization of plant resources to ensure sustainable development.Like other forms of biodiversity, the severe threats to TMPs are habitat loss and fragmentation, climate change, population pressure, and invasive species.Te study suggests that the conservation of TMPs should be promoted through cultural beliefs and norms, government laws and policies, the development of guidelines for the use of TMPs, the incorporation of local traditional cultural values in the national biodiversity conservation agenda, and their cultivation on farms and home gardens to overcome declining supplies and the risk of extinction from natural sources.So far, it is not well known whether overexploitation of TMPs is an issue in Tanzania.However, future ethnobotanical studies should also focus on how locals use and manage TMPs.Such studies will ofer an understanding of how locals in the country relate to the plant resources they use for therapeutic purposes.

Challenges of Integrating Traditional Medicine into
Modern Health Systems in Tanzania.Te WHO recognizes the important role of traditional medicine, including the TMPs, and endorses its integration into the healthcare system.In sub-Saharan Africa, nearly 85% of the population relies on traditional practitioners for their primary healthcare needs due to limited access to modern facilities [86].It should be noted that integrating traditional medicine into national health systems can increase access to primary health care for many people who only seek the services of traditional health practitioners [109].Integration can be predominantly benefcial in dealing with health crises such as pandemic outbreaks.Regardless of the opportunities and eforts done by the government of Tanzania, the integration of traditional medicine into modern healthcare systems still faces several challenges, not limited to those outlined below.

Absence of Essential Resources and Scientifc
Validation.Notwithstanding the growing national recognition of traditional medicine in the country, its incorporation is hindered by the lack of necessary resources and operational policies to expedite integration.While an appreciable proportion of traditional medicines is deeply rooted in cultural and spiritual practices, adequate scientifc Te Scientifc World Journal validation is lacking.Additionally, the fundamental resources for research to address the challenge are insufcient.

Inadequacy of Well-Trained Traditional Health
Practitioners.Te scarcity of well-trained traditional health practitioners (THPs) to advocate and pioneer the integration of traditional medicine into systematic health care is one ofshoot of the aforementioned challenges.Conventional medicine is primarily informal and does not require formal education or professional training as it passes from generation to generation orally.Terefore, it is susceptible to fraud and dishonesty, and practitioners' unproven medical claims are encouraged to thrive.Tese features of the practice incite a lack of trust in traditional medicine among the public and modern medicine practitioners.
3.9.3.Tere Are No Regulatory Frameworks for Quality Control.Ensuring the quality, safety, and efcacy of herbal medicines and associated services is fundamental.

Potential Confict between Traditional and Modern Medical Practices.
For example, while the country has made eforts to integrate conventional and complementary medicine into its health system, regulating the subsector has remained a challenge due to the lack of information and operational factors facing the regulatory frameworks in the country.
3.9.5.Knowledge Transfer.Te transmission of knowledge and ethical utilization of intellectual property are vital to the growth and development of science.Nonetheless, most traditional medicine practitioners neither practice proper documentation nor observe a systematic knowledge-sharing approach.Instead, knowledge is commonly shared orally with some individuals in the conventional medicine feld.Tis transfer of knowledge is done casually, often spanning years, and potentially contributes to knowledge loss, given the possibility of death.Furthermore, the fear of creating competition sometimes surpasses the desire to provide care, leading to knowledge hoarding.Also, the unethical utilization of traditional medicine knowledge gained from traditional practitioners by researchers without appropriate acknowledgment is another reason for the increased hesitancy of some traditional health practitioners to share their knowledge.

Conclusion
Since time immemorial, TMPs have been used to manage diferent human ailments, including asthma.In Tanzania, sixty-two TMPs are being used to treat asthma.Most of the recorded TMPs belong to the families Fabaceae and Rubiaceae.Trees and leaves are the most utilized life forms and plant parts, respectively, and most plant materials were collected from the wild areas.Decoction is the principal method of preparing remedies, and most herbal remedies are administered orally.Consideration must be given to the sustainable harvest of these TMPs so that future generations can enjoy what others have already enjoyed from Mother Nature.Also, given the signifcant number of TMPs that have not been scientifcally studied, pharmacological research is needed to identify the bioactive ingredients responsible for the therapeutic efects connected with the preparations' use, and safety/toxicological studies involving the herbal remedies are obligatory, too.Also, in view of the popularity of the listed TMPs, there is a need to design clinically relevant randomized clinical trials for herbal remedies in the management of asthma.Generally, this systematic review discloses the TMPs used by the locals in Tanzania against asthma and provides an entryway for future studies to discover and develop new modern drugs to manage asthma.

Figure 1 :
Figure 1: PRISMA fow diagram of the study.
Medicinal Plants (TMP)Regions with anti-asthmatic report (s) Regional boundary

Figure 2 :
Figure 2: Map showing distribution and number of antiasthmatic traditional medicinal plants (TMPs) in Tanzania.

Msaka
Leaves and bark are powdered, then mixed with honey, and taken orally[47] Not found Te Scientifc World Journal

Figure 3 :Figure 4 :
Figure 3: Percent share of plant parts used for making antiasthmatic herbal remedies.

Table 1 :
Medicinal plants used traditionally to manage asthma in Tanzania.

Table 2 :
In vivo antiasthmatic activity of some of the traditional medicinal plants used in Tanzania.