Traditional knowledge, medicinal plants, bioactive constituents, and prospecting technology: potential control of fungi

The use of plants with medicinal properties for fungi control has led to a continuous exploration of new compounds that could contribute towards promising studies in the development of new drugs and the knowledge of how this control is performed on microorganisms. The objective of this review has been to report on the potential use of medicinal plants to control the pathogenic fungi of a host of plants and animals, which can contribute to the achievement of new formulations for botanical fungicides. Many authors have demonstrated antifungal and general antimicrobial activities for Brazilian flora species through well-established methods, such as by microdilution, agar diffusion, and disk diffusion, while determining a minimum inhibitory concentration (MIC), minimum fungicidal concentrations (MFC), and the inhibition potential of essential oils, extracts and fractions. In this review, 68 species were cited for occurring in Brazil, with 25 being in the north-northeastern part of the country. Thus, most studies about the antimicrobial activities of medicinal plants bring an ‘initial understanding’ of their potential, particularly of some species, genera, and even families. Nevertheless, more data that is exceedingly specific is mandatory by focusing on new and more accurate approaches, such as the action mechanisms, toxicity, the active components, and the verification of the existence of synergic effects. These criteria would be the minimum required to develop new natural products as alternative treatments for the various infectious pathologies that affect plants, animals, and human beings.


Introduction
Humans acquired information about their environment in such a way as to build and establish tools that facilitate their survival. One field has been extensively exploited since ancient peoples, tribes, and communities know about plant species, their relationship to food, and medicinal purposes, with this know-how still being maintained and disseminated in the modern era. Despite a gradual loss of traditional knowledge, most of the world's population still enjoys these nutritional benefits, especially when dealing with medicinal plants (Quinlan & Quinlan, 2007). About 80% of developing countries still employ traditional folk knowledge in treating symptoms and illnesses. In addition, modern pharmacopeia has 25% of its drugs derived from plants. Given the current global scenarios, the quest for sustainability has increased a great deal of interest in "green" products for both industries and developed countries (Setshogo & Mbereki, 2011).
The so-called traditional medicines are a habit in local communities around the world. About 3.5 billion people use these resources in some way. About 70%-80% of traditional healers use traditional medicine in routine health care (Bekalo et al., 2009). In Asia, the number of plant species used for medicinal purposes is over 6,500 (Batharrai et al., 2010), with over 3,000 of them occurring in India alone (Mazid et al., 2012).
In Brazil, flora and fauna are an undeniable wealth, and a great interest in deepening and developing the knowledge of plants with medicinal properties, as shown by the increasing number of scientific papers on Brazilian medicinal plants, demonstrating that traditional knowledge has been seriously valued by the scientific community (Brito & Senna-Valle, 2011).
The SUS (Sistema Único de Saúde -Unified Health System), better known as Brazil's publicly funded health care system, in 2005 proposed the inclusion of herbal plants as therapeutic alternatives for health problems. However, herbal medicines' production is still considered incipient (Argenta et al., 2011).
There are numerous therapeutical applications of medicinal plants in Brazil, emphasizing antidiuretic, expectorant, healing, anti-inflammatory, and anti-rheumatic properties (Argenta et al., 2011). Other possible effects that are also widely exploited in alternative therapies are soothing remedies, analgesic, antipyretic, anti-cough, bronchitis, influenza, and pneumonia curatives, as well as for contusion injuries in general (Brito & Senna-Valle, 2011). In a small Brazilian community, the very same species was cited for more than 40 applications, ranging from asthma and heartburn to prostate cancer, as well as for the strengthening of hair (Vendruscolo & Mentz, 2006). Infectious diseases kill approximately 50,000 people daily.
Pathogens, especially in humans, have developed various resistance mechanisms to commercial drugs, generating a series of clinical complications and health policies. In addition, there are innumerable side effects and adverse reactions caused by these aforesaid commercial drugs (Namita & Mukesh, 2012).
Several diverse plants in Brazil have been reported to present antimicrobial activities, with over 20% of plant species described. For instance, gram-positive and gram-negative pathogens were susceptible to the decoction of Baccharis trimera Less. and Achillea millefolium L. has been effective against bacteria and fungi, as has been previously demonstrated in extracts of Allium sativum L., Maytenus ilicifolia Schrad., and Psidium guajava L. Extracts of Cynara scolymus L. and Achyrocline satureioides Lam. have inhibited the growth of Bacillus spp. and Pseudomonas, Staphylococcus aureus, whereas Vernonia polyanthes Less. has been effective against Leishmania spp., even though it has not demonstrated antibacterial or antifungal effects (Silva & Fernandes-Junior, 2010). For antimicrobial activities of plants, quite a few methods have been commonly applied. Tests and protocols selected for an evaluation in the literature vary greatly, providing different approaches to study. However, they are mostly discussing a wide variety of plant groups with compounds that can be exploited. Polyphenols and other phenolic compounds, such as catechol and pyrogallol have been analyzed, demonstrating an enzyme inhibition. Quinones are aromatic rings that bind irreversibly, reacting with the nucleophilic amino acids, inactivating the proteins.
However, antimicrobial activities have not been fully described for many chemical compounds, especially for essential oils. The secondary metabolites are composed of a complex mixture of compounds, such as monoterpenes, sesquiterpenes, phenylpropanoids, fatty acids, and their derivatives. They can be found in many different secretory structures of plants, and they play an essential role as signaling molecules while also attracting pollinators (Zuzarte et al., 2011). Their complex composition of the primary compounds as concentrations of each component in the essential oils gives uniqueness to the oils. Due to these unique characteristics, these compounds have received a certain number of scientific approaches in recent years. Their market value has been raised upwards by various manufacturers like the pharmaceutical, agricultural, food, health, and cosmetics industries (Zuzarte et al., 2011). Research, Society andDevelopment, v. 10, n. 13, e355101321410, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i13.21410 4 The antimicrobial activities of essential oils have been widely covered in studies from around the entire world. For instance, on the website for the CAPES (Brazilian Federal Agency for the Improvement of Higher Education) journals, the "antimicrobial" terms of "essential" and "oils" show an outcome of more than 8,000 results. Researchers have shown a keen interest in evaluating plants' essential oils while considering their antimicrobial properties in traditional medicines and alternative therapies (Luangnarumitchai et al., 2007). In Brazil, this trend is very significant. There are countless studies, from all regions of the country, analyzing and finding the antimicrobial potentials of various genera and species, many of them already known by the country's population and the scientific community (Borges, 2012;Costa, 2008;Zacaria, 2006;Vilela, 2008).

Methodology
This study is descriptive and exploratory with a quantitative approach (Sakamoto & Silveira, 2019). Use bibliometric analysis of articles contained in the Scopus (http://www.scopus.com) and Web of Science (http://www.webofknowledge.com) databases that were prospected in title or abstract of scientific articles. The present research is a meta-analysis, a quantitative method that combines the information obtained from previous independent studies and critically analyzes these results (Hernandez et al., 2020).
Thus, this current prospection has aimed to present data confirming the antimicrobial potentials for various species of medicinal plants in Brazil, mainly focusing on their fungal control, either phytopathogenic or upon human pathogens, such as viruses and bacteria prions, or fungi.
The data for this work was obtained by using scientific papers that have been previously published in indexed journals and which were internationally recognized in the CAPES periodical database. The technological prospection was realized

Results
The terms "antifungal," "essential," and "oil" when using "quick search" tools resulted in 62, 43, and one application in the Espacenet, WIPO, and USPTO databases, respectively. In the INPI database, for the terms "oils," "essential," and "fungi" two patents were found. The antimicrobial activities of plants for the pathogens in humans are presented in Table 1. Lippia spp. was a genus with over 200 species, with most of these widely used in popular medicine. Countless works have already been carried out regarding the antimicrobial properties of these essential oil species, backed up with assertive solid data, reinforcing the high potentials of genera against a significant number of microorganisms of sanitary, ecological, veterinary, agronomic, or human relevance. The Lippia sidoides Cham. the essential oil was tested with the Candida spp. and Microsporum canis pathogens. The tests were with agar disk diffusion and broth microdilution. At first, the strains were cultivated in potato dextrose agar. The receiving wells were made in the center of an agar medium plate. 100 μL of essential oils were added at concentrations ranging from 25 to 100 mg mL -1 and then diluted in mineral oil. The results were observed after five days.
A two-fold serial dilution was performed for the microdilution tests, with concentrations of between 5 mg mL -1 and 0.002 mg mL -1 . In addition to the minimum inhibitory concentrations (MIC), the minimum fungicidal concentrations (MFC) were determined by 100μL of inoculum in the wells and whose concentrations caused a total inhibition, while at the same time, lacking any turbidity.
The inhibition zone of M. canis was significant for the lowest concentration, totally restraining growth from 50 mg and T. rubrum strains were also analyzed. The simple cultivations of these strains in a medium with dilutions of the essential oil in DMSO defined the MIC levels, which came to be the lowest concentration in which there was fungal growth. Moreover, the oil's potential against Leishmania braziliensis and Trypanosoma cruzi was evaluated by applying essential oil solutions from 500 to 0.8 μg mL -1 , and after 48 hours, the IC50 was determined the MTT assay.
In the antibacterial assays, the P. malacophyllum essential oil had the potential to be considered weakly effective. Its antifungal activity was classified as being moderately effective only against T. mentagrophytes and C. neoformans. Its antiparasite effects were taken as being generally low once the IC50 was over 300 μg mL -1 (Rebelo et al., 2012).
The potential of the Calendula officinalis L. essential oils against 23 fungi strains, some of them clinically isolated, were tested against 22 Candida sp. strains and one Rhodotorula sp. strain. The essential oils were trialed by disc diffusion tests, with the paper discs soaked in essential oil and laid over a Muller-Hinton medium (Gazim et al., 2008). High inhibitory levels were observed in the C. dubliniensis and C. guilliermondii strains, whereas the variances of the oil effects were more elevated than Nystatin. It must be underlined that a high sensibility range of this microorganism can be a valuable feature for using the C. officinalis essential oil. (1,000 to 7.8 μgmL -1 ) acquired by a two-fold dilution. After that, the MIC levels were defined by concentration, in whose wells were seemingly straightforward. All appointed plants significantly affected at least one tested strain (Johann et al., 2007).
The oils of S. terebinthifolia showed higher activities against C. krusei, C. glagrata, and S. schenckii. The same MIC levels were found for C. neoformans from the B. dracunculifolia and P. regnellii extracts; the latter was also effective against C. tropicalis, while R. urticaefolius inhibited the growth of S. schenckii and H. crispa restrained the growth of C. neoformans.
The studied species held strong antifungal properties (Johann et al., 2007).
Work was developed with malva-do-cerrado (Hyptis ovalifolia Benth.) to evaluate the antifungal activities of its essential oil against the M. canis, M. gypseum, and Trichophyton mentagrophytes strains, as well as the clinically isolated T.
rubrum strain. The chosen approach was by using an agar diffusion. When placed into a solid medium, these dispersions were added to a still liquid Sabouraud-Dextrose medium and a later fungi suspension of inoculum. The MIC levels were checked with 31.2 μg mL -1 , and all of the tested fungi were inhibited, testifying the antifungal activities to be equal or better than control (Itraconazole) (Oliveira et al., 2004). which is usually known as Citronella, against the Trichophyton mentagrophytes strains. The agar disk-diffusion method was applied by using the pure essential oil soaked into filter paper disks. These were seated in a Sabouraud-Dextrose medium containing 1 mL of standardized conidia inoculum. The MIC levels were determined by a broth micro dilution when using 96well plates to apply a two-fold dilution of the oils to the fungi-inoculated wells. The MFC levels were obtained by employing 20 μL aliquots from the wells, resulting in no apparent growth to the clean culture plates. These pure essential oil dilutions could inhibit the strains. The lowest MIC level obtained was 156 μgmL -1 . The MFC levels that were found were, generally, eight times higher than the MIC levels. In the viability cell tests, the fungi solution was exposed to various oil concentrations and after 3.6, 9 and 12 days, it was observed that there was a gradual decrement of viability over time, reaching 100% after nine days. It was confirmed that the antifungal activities of C. winterianus were related to the damage of the cell membrane's integrity and the functionality of the T. mentagrophytes, possibly due to their lipophilic properties.

Aqueous and hydroalcoholic extracts of
Another multidisciplinary study was adopted that focused on C. albicans of the Amazon. The exotic species that stood out for their intense widespread use were Copaifera multijuga, Carapa guianensis Aubl., Piper aduncum, Piper hispidinervum, Annona glabra L., Azadirachta indica A. Juss, Bryophyllum calycinum Salisb., Eleutherine plicata Herb., Mammea americana L., Psidium guajava var. and Syzygium aromaticum L. A 32% solution of the essential oils was prepared, and it was serially diluted until it had a concentration of 2%.
Likewise, the extracts were tested by agar disk-diffusion, except for the filter paper disks, which were centrally placed on the yeast-cultivated plates. For MIC microdilution tests were performed. Of the seven tested extracts, E. plicata, P. guajava and S. aromaticum showed the highest effects. None of the essential oils presented any significant activities. However, most of the plants that have been related to this work have previous reports concerning antimicrobial activities of their essential oils or their isolated compounds (Menezes et al., 2009).
A lack of methodology standardization is a limitation in reported studies of essential oils. It is common to see expressive approach variations among the works, such as when the dilutions have been made by percentages (%) or by the mass over final volume (μg mL -1 ). In These cases, density oils vary within and between the species, mainly because of the differences in composition and the compound's concentrations. Therefore, the percentages of oils in each concentration ensures a parity in the volume of oils used, but this is not the same as the oil's mass, which may complicate the evaluation of each oil's potential, as suggested by Menezes et al. (2009). Variations in compounds composition and concentrations, the usage results for any given dilution in distinct surveys may diverge due to the contrast in compositions of the samples in each study.
Another fragility in the standardization of antimicrobial tests with essential oils is in their physical-chemical features.
For a solid or a liquid culture media, both have a hydrophilic character. Thus, when solubilizing oils, which are essentially hydrophobic, it is necessary to perform such actions in a medium. Different alternatives must be considered, either in choosing the solvent or by merging the oils in a medium. In the main, these alternative methodologies are likely to be efficient, for they allow for verification and quantification of the oil's potential, as reported by Sarmento-Brum et al. (2013). However, the diversity of the applied approaches prejudices a result's comparison, as the used parameters and resources are not always corelatable.
The antimicrobial activities of plants for pathogens are presented in Table 2. The chemical compounds for a phytopathogen control in agriculture is an easily confirmed fact. However, in the same way as these compounds are increasingly used, the risk of their application in crops, has in many cases, been underestimated. On the other hand, there is a growing commercial demand for food produced with organic certification, especially when using natural products for disease control. Thus, this research using plant medicinal compounds may be interesting for the agricultural industries (Table 2). The essential oils from Eremanthus erythropappus, Cymbopogon martinii, and Rosmarinus officinalis were tested against the mycelial growth of Alternaria spp, Rhizoctonia solani (Hillen et al., 2012). Different aliquots were tested on the BDA medium. Mycelial discs were laid on the center of the plates, and the halo diameters were measured daily. The Mycelial Growth Index was estimated based upon the growing and the negative control. All the phytopathogens were inhibited by the E.
elytropappus oils, with more significant effects over R. solani and Alternaria spp. In just the higher concentrations, the R.
officinalis oils inhibited the fungi as well. However, the best inhibitory effect was observed by C. martinii, which suppressed the growth of all the concentration strains tested. Therefore, it is conclusive that the essential oils of the three species mentioned above are distinctly efficient against Alternaria spp. and R. solani.
In pursuit of a solution to control Sclerotinia sclerotiorum in a soy stem without any agro-toxic effects, Garcia et al. The samples of Piper dilatatum Rich., P. cyrtopodon Miq., P. hostmannianum Miq., P. callosum Ruiz and Pav., P.
tuberculatum Jacq., P. divaricatum G. Mey., P. nigrispicum C. DC, P. hispidum Sw., P. marginatum var. anisatum Jacq. and P. enckea C. DC. were collected, and their oils were extracted by hydro distillation. The agar diffusions and the dilutions of the oils that were incorporated into the founding medium were tested. Their effects against the germination of C. perniciosa were also analyzed. C. perniciosa was inhibited by low concentrations of the P. callosum oils and 1 μL mL -1 of the P. marginatum oils. When relating to P. palmivora, only P. callosum and P. enckea showed any effectiveness, and P. callosum induced a 100% inhibition of P. capsici. In the C. perniciosa basidiospores assays, the P. dilatatum, P. callosum, and P. marginatum oils were effective, inducing a complete inhibition of the germination at low concentrations.
Another study evaluated the essential oils of Cymbopogon nardus (L.) Rendle against the Rhizoctonia solani fungus.
The micelle discs were laid in every plate, and the fungal growth was observed during ten days of incubation. By the end of the tests, all treatments presented lower growth rates when compared to control until the eighth day (Sarmento-Brum et al., 2013).
Oliveira Junior et al. (2013) investigated the in vitro and in vivo antifungal activities of the S. terebinthifolia Raddi. essential oil over the Colletotrichum gloeosporioides strain that was cultivated in BDA. The essential oils were obtained by hydro distillation. The in vitro dilution of the oils was realized directly in the medium. Paper filter discs were placed in the center of the plates, and the spore suspensions were inoculated onto the discs and plates. Measuring the colony diameters were performed 2, 4, 6, and 8 days after the inoculation. For the in vivo tests, the papaya solo-type fruits were harvested and disinfected with calcium hypochlorite. The injuries were produced on the fruits using entomological needles, and 3μL spore solutions were inoculated. These fruits were wrapped with starch biofilm with 0.5% of the essential oil. It was found that the highest concentration could inhibit 79% of the mycelial growth of C. gloeosporioides. In the in vivo tests, the fresh mass loss was 70% when using the oil, against 40% for control. for dilutions lower than 10% and all the fungi at 25% (Santos et al., 2010).
A study was performed to analyze the antifungal activities of the Cymbopogon nardus L. Rendle essential oils over the mycelia of Fusarium subglutinans that were isolated from pineapples. Aliquots of the oils were added onto the surfaces of the BDA. The evaluations occurred every 48 hours by measuring the culture halos, totaling five checks per plate. The three highest aliquots performed 100% growth inhibition until the fourth evaluation day. A 25 μL aliquot pointed to a mycelial growing rate of 1.55 mm day -1 , while the control showed an 8.56 mm day -1 growing rate. The citronellal majority chemical compound effect was evaluated. It presented a growth rate of 3.36 mm day -1 , suggesting that the synergism possibly gave the highest efficiency of the essential oils among most oil compounds (Seixas et al., 2011). The extracts were blended in the BDA medium, and essential oils were inoculated at three equidistant points on the medium's surface. The S. aromaticum aqueous extracts inhibited 100% of the pathogens. The P. australis and elderberry extracts did not show any inhibitory effects on any of the fungi. Lippia, lemongrass, and calendula extracts were not effective against G. cingulate, and the extracts of "cavalinha," basil, and mint were not effective against C. gloeosporioides. The clove and lemongrass essential oils inhibited the growth of C. gloeosporioides until the fifth day. At the same time, the lemongrass oil also suppressed the growth of G. cingulata, reducing its inhibition potential from 100% to 62.8% on the eighth day. This reduction might have been due to the volatilization of some of the oil compounds.
The properties of the essential oils suffer from several variations, with differences in their pH, density, coloring, volatility, fusion point, and viscosity. These are only a few examples of the features directly associated with the chemical compositions of the essential oils. On the other hand, the compound varies to many factors, such as geographic localization diversity, age, extraction methods, planting season, and more.
Various antimicrobial activities of the essential oils were determined primarily by their chemical composition, either from the isolated compounds or from the synergism between the majority and minority compounds, resulting from their intervention in the pathogen metabolic pathways. Therefore, the conditions that influence the composition variations of the essential oils are significant for upcoming studies about their antimicrobial activities. Hence, it is essential to consider such conditions before developing new assignments or comparing literature data that discusses certain species and their potential.
The essential oils that have been reviewed may have presented countless positive results, but some samples did not render any equivalent efficiencies.
The substances mentioned therein have been tested, and the traditional knowledge associated with them has been proved. However, little is known about how fungal control is established, given a molecular and genetic outlook. Thus, most studies about the antimicrobial activities of medicinal plants bring an 'initial understanding' of their potential, particularly of some species, genera, and even families. Nevertheless, more data that is exceedingly specific is mandatory by focusing on new and more accurate approaches, such as the action mechanisms, toxicity, the active components, and the verification of the existence of synergic effects. These criteria would be the minimum required to develop new natural products as alternative treatments for the various infectious pathologies that affect plants, animals, and human beings. Sixty-eight species were mentioned in the literature, all occurring in Brazil, with 25 occurring in the Brazilian north-northeastern region.