1 Introduction
The Amazon rainforest, belonging to the Brazilian territory, has a diversity of plants and plant species, including native ones little or not at all investigated. Fruits commonly used in the locus, such as bacaba (Oenocarpus bacaba Mart), pracaxi (Pentaclethra macroloba Kuntze) and uxi (Endopleura uchi (Huber) Cuatrec), are potentially relevant for studies of natural products, as vegetable oils are known to have beneficial health effects, in addition to being abundant and readily available renewable resources1).
Bacaba one of the most studied species, has valuable nutritional potential, as its oil is rich in unsaturated fatty acids, nonetheless, there is little knowledge about it, mainly about its chemical composition2),3).
Pracaxi provides oil with high concentrations of oleic, linoleic and behenic fatty acids, and the oil extracted from the seeds of this plant has been used for therapeutic activities such as wound and cut healing, skin hydration and cell renewal, and other dermatological1),4).
Like these species, uxizeiro popularly known as “uxi-amarelo” or “uxi-smooth”, presents antioxidant action, its bark is used in the preparation of teas and is indicated as an adjuvant in the treatment of diseases of the female urinary tract, inflammation of the uterus, diabetes and arthritis5),6),7),8).
To date, the published reviews about the fruits from the Amazon biome are scarce. A review evaluating the use of nutraceuticals prepared from fruits and seeds from the Amazon did not consider the bacaba, pracaxi and uxi oils9). These reviews did not perform a systematized mapping of information about the biomes9),10).
This scoping review can assist researchers in the development of phytomedications from the Amazon biomes and as well as increase the options of medications in the therapeutic arsenal of the Unified Health System (Sistema Único de Saúde, SUS)11). Therefore, the current study aims at mapping and characterizing studies on the bacaba, pracaxi and uxi species, belonging to the Amazon rainforest.
4 Discussion
The studies included point to the Brazilian biodiversity, as it has in its territory biomes rich in animal and plant species, such as the Amazon9),16),17),18),25),28),29),39). Among the plant classes, there is bacaba, pracaxi and uxi.
Twenty-one articles included in this review were conducted in northern Brazil. The fruits belong to native trees in this region of the country, which explains the widespread use by the local population40).
Plants have been important sources of constituents with pharmacological activities, especially fatty acids. This justifies the fact that this class was mentioned among the studies on these oils, indicating their potential and nutritional quality7),17),21). Oleic acid, for example, which was mainly present in all oils, ranging from 30.7% to 72.16%, due to its hypocholesterolemic action, has the advantage of not reducing High-Density Lipoprotein (HDL) cholesterol43). It is considered promising for pharmaceutical formulations because it has properties that improve wound healing27).
Linoleic acid, reported in six studies, when ingested, through the action of the elongase and desaturase enzymes, undergoes an unsaturated reaction and is converted into longer-chain polyunsaturated fatty acids44),45). These compounds are present, for example, in the production of hormones such as Series 3 Prostaglandin, which regulates and protects the body against various effects, such as platelet aggregation (due to its antithrombotic activation) and reduces the risk of cardiovascular diseases44).
In addition to the fatty acids found predominantly in all species, some studies5),6),36),37),38),40),41),46) cited another chemical class identified as dominant in uxi: Bergenin, a C-glycoside from 4-O-methyl gallic isolated from several medicinal plants with multiple biological activities. Its antimalarial, antidiabetic, anti-cancer, gastroprotective, antituberculosis, antiarrhythmic, hepatoprotective, antiviral, antiangiogenic, neuroprotective, immunomodulatory, antimicrobial, hypolipidemic, healing, antioxidant, anti-hyperuricemic activities and anti-inflammatory properties stand out47). This suggests that this plant has great potential to be used as a therapeutic agent for the development of more effective and safer phytomedications48).
A number of research studies also cite the presence of phenolic compounds16),30) such as α-tocopherol, commonly known as vitamin E, and considered one of the best natural antioxidants in the bacaba and pracaxi species, and this demonstrates the antioxidant profile and potential therapeutic application against inflammatory diseases of these plants16),29). Inflammation and oxidative stress are related to phenomena involved in pathological conditions such as cardiovascular and phenolic compounds that can contribute to the reduction of inflammatory events49).
Several therapeutic applications were mentioned for the species chosen for this study. Some authors agree on the protection that bacaba confers against cardiovascular diseases17),21),42). As well as others, which inquired that pracaxi has anti-inflammatory and healing actions and prevents chronic diseases such as cancer, cardiovascular and neurodegenerative diseases, respectively23),26),28).
For uxi, the records indicate analgesic and anti-inflammatory activities to treat arthritis, cholesterol, diabetes, uterine infections and fibroids34),46) for example. It also mentioned great antidiabetic potential35), antioxidant activity6),40) and the usefulness of this species in the treatment of coronary and cardiovascular diseases7).
Due to the antioxidant knowledge about the bioactive compounds present in these species, some studies have performed phytochemical assays for uxi5),33),35),36),39),40). These assays focus on models capable of discovering molecular profiles with high antioxidant power or even evaluating the antioxidant potential of a molecule already known and extracted.
The in vitro phytochemistry studies included in this review used extraction methods to obtain a specific molecule or molecular type. Among them, two evaluated antioxidant activity by the DPPH assay, considered a rapid methodology for this objective36),40). While one study found positive results for uxi’s in vitro antioxidant capacity, another reported low antioxidant activity of this species by this same methodology.
The planting modality and place are limiting factors in the cultivation of some species, as it is obvious that plants depend on climate and soil conditions27). This can be highlighted by the findings of the review, which identified different profiles of most of the products in the same species. Although most studies mention these predominant compounds, others did not perform this evaluation. It is of paramount importance to know the profile of these products since, although compounds isolated from plant extracts present biological activity, their crude extracts may not have all the desired characteristics50).
Although they are promising natural resources, studies related to the oils of the studied species (bacaba, pracaxi and uxi) have some limitations, such as variation of fatty acid concentrations according to temperature and pressure, which can directly influence quality of the final product formed by these plants and consequent oxidation19),21),26). In addition, when considering the development of formulations that have applicability in the pharmaceutical sector, it is necessary to choose chemically compatible constituents, as some substances may or may not present antioxidant activity when isolated27).
The methodologies used by two authors for extracting and obtaining pracaxi oil, respectively, require the use of solvents, which, despite showing positive perspectives, deserve attention regarding toxicity, as its traces can remain in the oil and, therefore, in the case of medicinal products, an adequate choice is needed28),32),50).
Although all studies have cited positive results for uxi, such as antinociceptive effects that inhibit cyclooxygenase46), the antiproliferative effect of this plant against HeLa cells34), inhibiting properties of α-glycosidase, antibacterials and cholinesterases35), substantial antioxidant activity in vitro and in vivo36), they showed the need for further research studies on the use of their extracts in therapeutic applications, as their biological activities, as well as their toxicological profile, are not yet elucidated36). In addition, few studies have been conducted in humans, and it is necessary to propose clinical trials, especially randomized and controlled, for a safety and efficacy measure.
From the statements related to the main bioactive compounds and the therapeutic potential identified in these species, however, some limitations emerge due to the absence of important parameters, such as, absence of clinical trials, heterogeneity of studies, methodological quantitative analysis, difficulties in large-scale exploration, variability extraction methods and others. In view of this, this review maps information from the literature that may help in the development of studies focused on this topic in the future, since more investigations and outcomes are needed for this population.
The therapeutic effects reported in the studies included in this review are, for the most part, assumptions that are not based on evidence, since this proof requires the performance of clinical trials that must be approved and monitored by ethical and regulatory authorities to ensure that the ethical conduct and technical aspects of research conform to the required standards51).
It is noted that there is potential in these plants for technological prospecting and investment in more economical, safe and sustainable products for the environment, especially because they meet the SUS epidemiological demands, as cardiovascular diseases, the main therapeutic activity elucidated, represent a significant percentage of expenses and availability of high-complexity services for public health52).
As they are considered an important source of biologically active natural products, there are some dilemmas regarding the development of medications, as it is necessary to use techniques that allow obtaining a final product with stability, quality and efficacy also for acceptability by the population, as suggested by studies involving the Evaluation of Health Technologies53),54). For the pharmaceutical sector, herbal medications can mean an opportunity for development, not only because of the abundance of the country’s fauna and flora, but also because of the traditional and scientific knowledge about the biological activity of plants55).
Although many Brazilian studies have shown promising results on bacaba, pracaxi and uxi, none of them proposed strategies for the sustainable use of these plants, nor have they presented any concern regarding environmental preservation in technological innovation. In this sense, it is necessary to conduct studies that prioritizes herbal medications, but also that include sustainable development from environmental awareness in their methodology56),57).
This scoping review followed the methodological guidelines proposed by the Joanna Briggs Institute and was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Extension for Scoping Reviews is provided in appendix additional 1 to document the completeness of reporting of this review (PRISMA-ScR) checklist12),13). As for limitations, there is the fact that only 2 scientific databases were consulted. Nevertheless, to mitigate publication bias, searches were conducted in the Grey Literature.
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