Known and unknown medicinal plants used in respiratory disorders in Brazilian folk medicine: a brief review

This review aimed to describe some plants used in Brazilian folk medicine in respiratory disorders, highlighting species not well known to the Brazilian citizens. The articles were surveyed in the MEDLINE / PubMed, Web of Science, SCOPUS / Elsevier, SciELO and Cochrane with the descriptors in Health Sciences (DeCS) databases: Medicinal plants, herbal medicine and respiratory diseases with the keywords: secondary metabolites and pulmonary disorders, considering the period from June 2010 to June 2020. The results indicated that species known as Mikania glomerata and Allium sativum, are well studied, presenting a large volume of publications and results on phytochemical and pharmacological aspects. In contrast, lesser-known species of the Brazilian population, such as Amburana cearensis, Hybanthus ipecacuanha, and Jatropha curcas, need more studies, which explore their potential in the medical field. Brazilian biodiversity offers a wide variety of medicinal plants, some of which are better known and studied; others less known and little studied, requiring further investigation in order to provide a scientific basis, both for the isolation and synthesis of molecules and for possible therapeutic applications in different respiratory diseases.


Introduction
Chronic Respiratory Diseases (CRD) can affect both upper and lower airways. The CRD represents approximately 7% of the global mortality that is 4.2 million annual deaths. In Brazil, the CRD already has been the third biggest death cause speaking on non-communicable respiratory diseases [1]. Allergic rhinitis, asthma and Chronic Obstructive Pulmonary Disease (COPD) are the most common CRD, being allergic rhinitis the most common one, afflicting approximately 20 to 25% of the population [1,2]. According to a study made by International Study of Asthma and Allergies in Childhood, conducted in Brazil, indicates that the rhinitis symptoms are present in 29.6% of teenagers and 25.7% of kids, indicating that the country has the world's highest rates of rhinitis. Regarding asthma, Brazil stands on the eighth worldwide position, having internated 273 thousand people and generating a cost of approximately R$ 98 million to the SUS (the Brazilian unified health system) [3]. In relation to COPD the morbidity and mortality has been increasing in many regions, representing 4.8% of deaths by respiratory diseases. The COPD has already afflicted approximately 7.5 million people that is 5% to 10% of the population [4].
Brazil has a wide biodiversity, with about 60,000 known species of plants [5]. The use of plants for therapeutic purposes has been present in Brazilian culture since ancient times and comes from different traditional cultures, mainly from Brazilian indigenous peoples. This practice was motivated by the growing demand for improvements in health and is present in primary health care in Brazil until today [6]. In the last decades, records of the use of herbal medicines indicate a considerable increase in this practice [7]. Before, in 2006, the National Program of Medicinal Plants and Phytotherapics was created [8], generating improvements for primary care and providing 12 phytotherapics for the population [6,8].
Recently, according to the Brazilian Ministry of Health, the issuing of National Relation of Essential Medicines pharmaceutical units for herbal medicines in the 26 states grew by 239,11% between 2012 and 2018 [7].
The literature provides many references about medicinal plants used in the treatment of respiratory disorders. For example, Eucalyptus globulus, for sinusites, bronchitis, and asthma [14,15]; Illicium verum for bronchitis [14]; Mikania glomerata and/or Mikania laevigata [14,15] for bronchitis and asthma; Allium sativum [14,16,17] for chronic bronchitis and asthma; and Hedera helix [18,19]  itself and/or with cells of other organisms, contributing to the coexistence and environmental survival [11,12]. The isolation and structural determination of the substances produced by these metabolites are of great relevance, mainly for chemistry and medicine [13] as they serve as a model for structural modification and optimization of properties pharmacological and biochemical, in addition to inspiring organic chemistry in the challenge of synthetic construction of new molecular architectures [11]. Thus, the biological activity of medicinal plants is associated to secondary metabolites, responsible for anti-inflammatory, analgesic and antimicrobial activities, etc. [20]. The present study aimed to document the traditional uses of medicinal plants known and unknown in Brazil in the treatment of respiratory disorders, correlating, whenever possible, their pharmacological action with the presence of secondary metabolites.

Methods
The   [27]. Also, it is widely used to treat indigestion, cardiac disorders and respiratory and urinary tract infections, being its acting in respiratory disorders one of the most relevant nowadays [27]. The antiasthmatic effect of Allium sativum extracts on the Th1, and Th2 cytokine profiles showed that Allium sativum was able to reduce total inflammatory cell counts and eosinophil infiltration and decreased the production of Dermatophagoides pteronyssinus IgE in serum and cytokine in bronchoalveolar fluid [29]. Allicin, the main active constituent of garlic, is a sulfenic acid thioester that has its pharmacological effect attributed to its antioxidant activity as well as its interaction with proteins containing thiol [27]. The Allium sativum also contains S-Allyl cysteine (SAC) in its constitution, an active compound that has anti-inflammatory, anti-oxidant, and anti-cancer activity [30]. Bax/Bcl-2 ration. [45] Bixa orellana L. or popularly, "colorau", "urucú", "tintória", and "urucum", is originally from tropical America, including the Brazilian Amazon.

anti-inflammatory, antihypertensive and
bronchodilator activities, justifying the use in cardiovascular and respiratory disorders [60,61].

Cajanus indicus L., cultivated in the tropics
and subtropics mainly in Asia and Africa [62].
Although used by the population to treat respiratory disorders, we have not found studies that justify this medicinal use.
In the respiratory system, the P. lancifolia is used to asthma [67,68] treatment and chronic bronchitis [67].