Essential Oil of Bursera morelensis Promotes Cell Migration on Fibroblasts: In Vitro Assays.

Essential oils (EOs) are complex mixtures of volatile natural compounds. We have extensively studied the EO of Bursera morelensis, which demonstrates antibacterial, antifungal, anti-inflammatory, and wound-healing activities. The objective of this work was to determine the effect of this EO on fibroblast migration in a three-dimensional in vitro model. For the three-dimensional in vitro model, a series of fibrin hydrogel scaffolds (FSs) were built in which fibroblasts were cultured and subsequently stimulated with fibroblast growth factor (FGF) or EO. The results demonstrated that these FSs are appropriate for fibroblast culture, since no decrease in cell viability or changes in cell proliferation were found. The results also showed that this EO promotes cell migration four hours after stimulation, and the formation of cell projections (filopodia) outside the SF was observed. From these results, we confirmed that part of the mechanism of action of the essential oil of B. morelensis during the healing process is the stimulation of fibroblast migration to the wound site.

Biological Activity of Bursera schlechtendalii Essential oil and the Roles of Its Chemical Components in the Wound Healing Process.

Essential oils are composed of terpenes, some of which have properties related to healing. Bursera schlechtendalii essential oil (BSEO) is used to heal superficial wounds. However, there have been no studies verifying this property. The objectives of this study were to evaluate the healing activity of BSEO in a murine model and to propose the roles of its chemical components in this process. Healing activity was evaluated by an incision model, histological analysis was performed, and tensile strength and antibacterial activity were measured. The chemical composition of BSEO was determined by gas chromatography coupled with mass spectrometry (GC-MS), and the mechanisms of action of each chemical component during the phases of the healing process were proposed. In addition, acute dermal toxicity was evaluated. BSEO showed better wound closure at the macroscopic, histological, and tensile strength levels compared to controls and had an antibacterial effect. The major compound in BSEO was α-phellandrene. However, most of the monoterpenes identified in BSEO were in agreement with information found in the literature, so the possibility of synergy between the chemical components and their different targets in the healing process was schematically proposed. BSEO was shown to be safe in the dermal toxicity evaluation.

Composición química y actividad AChE-BuChE del aceite esencial de palo santo Bursera graveolens (Kunth) Triana & Planch de Jipijapa, Ecuador / Chemical composition and AChE-BuChE activities of the essential oil of palo santo Bursera graveolens (Kunth) Tr iana & Planch from Jipijapa, Ecuador

Abstract: This article describes the chemical composition, physical properties and acetylcholinesterase (A ChE) and butyrylcholinesterase (BuChE) activity of stem - distilled essential oil (E O ) from Bursera graveolens wood chips, Burseraceae. The plant material was acquired in Quimis (Bosque de Sancán), city of Jipijapa in the province of Manabí, coastal region o f Ecuador. Thirty - six components were identified by CG - MS, which represented 98.54% of the volatile oil. The main components were limonene (68.52%) and mentofuran (20.37%). The hydrocarbon monoterpenes constituted the most abundant fractions. The average y ield of the E O was 1.26%. Regarding the physical properties of E O , the following values were obtained: relative density (1,029 g/mL), refractive index (1,477) and specific rotation (+4,567). The E O presented IC 50 inhibition values of 47.2 and 51.9 µg/mL fo r the enzymes AChE and BuChE, respectively.

Resumen: Este artículo describe la composición química, propiedades físicas y actividad acetilcolinesterasa (AChE) y butirilcolinesterasa (BuChE) del aceite esencial (AE) destilado a vapor de astillas de madera de Bursera graveolens , Burseraceae. La materia vegetal fue adquirida en Quimis (Bosque de Sancán), ciudad de Jipijapa en la provincia de Manabí, región costera d e Ecuador. Treinta y seis componentes fueron identificados por CG - MS, que representaron al 98.54 % del aceite volátil. Los componentes principales fueron limoneno (68.52%) y mentofurano (20.37%). Los monoterpenos hidrocarburos constituyeron las fracciones m ás abundantes. El rendimiento medio del AE fue de 1.26%. Con respecto a las propiedades físicas del AE se obtuvo los siguientes valores, densidad relativa (1.029 g/mL), índice de refracción (1.477) y rotación específica (+4.567). El AE presentó valores de inhibición IC 50 de 47.2 y 51.9 µg/mL para las enzimas AChE y BuChE, respectivamente.

Preliminary prospection of phytotherapic compounds from the essential oils from barks and leaves of Umburana (Commiphora Leptophloeos)

Abstract The potential of the biome caatinga (exclusive from northeastern Brazil) has been evaluated in recent research for application in the pharmaceutical industry. Among the species of medicinal plants from caatinga, one can highlight the Commiphora leptophloeos (umburana), which has been used as infusions and syrups by the regional population for inflammatory and infectious diseases. Essential oils from umburana leaves and barks were obtained in a Clevenger apparatus and analyzed by gas chromatography/mass spectrometry, and total phenolic and flavonoids were determined by spectrophotometric analysis. It was observed that a large part of the major compounds present in the essential oil is described as having antitumor activity, enabling research in investigational oncology with umburana (C. leptophloeos). In addition, some little explored components have been identified, such as cadinene, alpha-selinene, and elemenone. Despite being easily found in several plants, there are no clinical trials involving their biological activity in a well-defined isolated form, which could make exploring new studies possible. Furthermore, the presence of phenolic compounds and flavonoids allows future studies about the potential antimicrobial and antioxidant activity.

In Vitro Anti-Tubulin Activity on MCF10A Cell Line and In Silico Rigid/Semiflexible-Residues Docking, of Two Lignans from Bursera Fagaroides var. Fagaroides.

Podophyllotoxins are natural lignans with known cytotoxic activity on several cell lines. The structural basis for their actions is mainly by the aryltetralin-lignan skeleton. Authors have proposed a cytotoxic mechanism of podophyllotoxins through the topoisomerase-II inhibition activity; however, several studies have also suggested that podophyllotoxins can inhibit the microtubules polymerization. In this work, the two possible mechanisms of action of two previously isolated compounds from the stem bark of Bursera fagaroides var. fagaroides: acetylpodophyllotoxin (1) and 5'-desmethoxydeoxypodophyllotoxin (2), was analyzed. An in vitro anti-tubulin epifluorescence on the MCF10A cell line and enzymatic topoisomerase II assays were performed. The binding affinities of compounds 1 and 2 in the colchicine binding site of tubulin by using rigid- and semiflexible-residues were calculated and compared using in silico docking methods. The two lignans were active by the in vitro anti-tubulin assay but could not inhibit TOP2 activity. In the in silico analysis, the binding modes of compounds into both rigid- and semiflexible-residues of tubulin were predicted, and only for the semiflexible docking method, a linear correlation between the dissociation constant and IC50 previously reported was found. Our results suggest that a simple semiflexible-residues modification in docking methods could provide an in vitro correlation when analyzing very structurally similar compounds.

Cytotoxic activity and triterpenes content of nine Mexican species of Bursera.

The genus Bursera (Burseraceae) is considered an interesting source of antitumour compounds. This study aimed to evaluate the cytotoxic activity of the dichloromethane-soluble extracts from the bark of nine Mexican Bursera species. The chemical components of the extracts were determined by NMR and mass spectroscopy, whereas its cytotoxicity was tested using the sulphorhodamine (SRB) method on seven cell lines. Triterpenes and fatty acids were the most abundant components found in the extracts. A quantification by HPTLC - densitometry, showed that the species B. copallifera had the highest content of amyrins (287 µg/mg extract) followed by B. submoniliformis (159.5 µg/mg) and B. bicolor (156.5 µg/mg). Regarding cytotoxicicity, the species B. bicolor caused the highest growth inhibition (>90%) in colon (HCT-15) and lung (SK-LU1) lines; while B. fagaroides, B. grandifolia, B. morelensis, B. bicolor and B. linanoe were active in the SK-LU1cell line.

Wound Healing Activity of the Essential Oil of Bursera morelensis, in Mice.

Bursera morelensis is used in Mexican folk medicine to treat wounds on the skin. It is an endemic tree known as "aceitillo", and the antibacterial and antifungal activity of its essential oil has been verified; it also acts as an anti-inflammatory. All of these reported biological activities make the essential oil of B. morelensis a candidate to accelerate the wound-healing process. The objective was to determine the wound-healing properties of B. morelensis' essential oil on a murine model. The essential oil was obtained by hydro-distillation, and the chemical analysis was performed by gas chromatography-mass spectrometry (GC-MS). In the murine model, wound-healing efficacy (WHE) and wound contraction (WC) were evaluated. Cytotoxic activity was evaluated in vitro using peritoneal macrophages from BALB/c mice. The results showed that 18 terpenoid-type compounds were identified in the essential oil. The essential oil had remarkable WHE regardless of the dose and accelerated WC and was not cytotoxic. In vitro tests with fibroblasts showed that cell viability was dose-dependent; by adding 1 mg/mL of essential oil (EO) to the culture medium, cell viability decreased below 80%, while, at doses of 0.1 and 0.01 mg/mL, it remained around 90%; thus, EO did not intervene in fibroblast proliferation, but it did influence fibroblast migration when wound-like was done in monolayer cultures. The results of this study demonstrated that the essential oil was a pro-wound-healing agent because it had good healing effectiveness with scars with good tensile strength and accelerated repair. The probable mechanism of action of the EO of B. morelensis, during the healing process, is the promotion of the migration of fibroblasts to the site of the wound, making them active in the production of collagen and promoting the remodeling of this collagen.

Volatile chemical composition of essential oil from Bursera graveolens (Kunth) Triana & Planch and their fumigant and repellent activities

The objectives of this work were the study of the volatile chemical composition of essential oils (EO’s) from Bursera graveolens obtained in the locality of Malagana, municipality of Mahates, Bolívar, Colombia, as well as to evaluate their repellent and fumigant properties. EO’s were extracted by hydro-distillation and characterized by gas chromatography-mass spectrometry (GC-MS). The major compounds found in B. graveolens were limonene (42.2%), pulegone (20.9%), carvone (7.5%), caryophyllene (4.1%), and trans-carveol (3.8%). The repellent activity of EO’s was determined by the area preference method, where the EO of B. graveolens presented repellent activity against the Tribolium castaneum weevil at a concentration of 1 at 2% and 4 hours of exposure (88.1 and 88.6% respectively). B. graveolens essential oil was more effective in its fumigant activity with LC50 of 108.2 μg oil mL-1. Also, the fumigant and repellent activities of two individual compounds present in the oil were evaluated, that is, limonene (majority) and caryophyllene. The results indicated that B. graveolens essential oil could be a promising alternative to new natural repellents and biocides.

Lignans from Bursera fagaroides Affect In Vivo Cell Behavior by Disturbing the Tubulin Cytoskeleton in Zebrafish Embryos.

By using a zebrafish embryo model to guide the chromatographic fractionation of antimitotic secondary metabolites, seven podophyllotoxin-type lignans were isolated from a hydroalcoholic extract obtained from the steam bark of Bursera fagaroides. The compounds were identified as podophyllotoxin (1), ß-peltatin-A-methylether (2), 5'-desmethoxy-ß-peltatin-A-methylether (3), desmethoxy-yatein (4), desoxypodophyllotoxin (5), burseranin (6), and acetyl podophyllotoxin (7). The biological effects on mitosis, cell migration, and microtubule cytoskeleton remodeling of lignans 1⁻7 were further evaluated in zebrafish embryos by whole-mount immunolocalization of the mitotic marker phospho-histone H3 and by a tubulin antibody. We found that lignans 1, 2, 4, and 7 induced mitotic arrest, delayed cell migration, and disrupted the microtubule cytoskeleton in zebrafish embryos. Furthermore, microtubule cytoskeleton destabilization was observed also in PC3 cells, except for 7. Therefore, these results demonstrate that the cytotoxic activity of 1, 2, and 4 is mediated by their microtubule-destabilizing activity. In general, the in vivo and in vitro models here used displayed equivalent mitotic effects, which allows us to conclude that the zebrafish model can be a fast and cheap in vivo model that can be used to identify antimitotic natural products through bioassay-guided fractionation.

Volatile Profiling, Insecticidal, Antibacterial and Antiproliferative Properties of the Essential Oils of Bursera glabrifolia Leaves.

The present article describes the chemical composition and biological activities of the essential oils of B. glabrifolia leaves obtained in four consecutive years (2015-2018). The essential oils contained α-terpineol (17.9-29.7 %), α-terpinene (12.6-17.4 %), limonene (14.9-26.8 %) and ß-pinene (2.1-16.7 %) as the most abundant volatiles. The essential oils and these volatiles showed a significant adulticide activity (p<0.01; LC50 <100 µg mL-1 ) on the maize weevil (Sitophilus zeamais) with a 100 % mortality rate within a period of 5 h. Also, the essential oils showed a strong antibacterial activity on Enterococcus faecalis ATCC 29212 (MIC, 132.7-173.6 µg mL-1 ) and Helicobacter pylori ATCC 43504 (MIC, 74.8-199.2 µg mL-1 ). The assessment of the main volatiles revealed α-terpineol as the principal antibacterial agent (MIC, 78.6-149.7 µg mL-1 ). Similarly, the essential oils exhibited a substantial in vitro antiproliferative activity on the human prostate cancer cell lines PC-3 (LC50 , 15.2-19.4 µg mL-1 ), the human ovarian carcinoma cell lines OVCAR-3 (LC50 , 27.3-53.7 µg mL-1 ) and the myelogenous leukemia cell lines K-562 (LC50 , 32.4-75.9 µg mL-1 ). α-Terpineol (LC50 , 32.4-75.9 µg mL-1 ) exhibited the strongest antiproliferative effect on these cancer cell lines (LC50 , 22.4-48.1 µg mL-1 ).

An Ethnopharmacological, Phytochemical and Pharmacological Review on Lignans from Mexican Bursera spp.

The genus Bursera belongs to the family Burseraceae and has been used in traditional Mexican medicine for treating various pathophysiological disorders. The most representative phytochemicals isolated from this genus are terpenoids and lignans. Lignans are phenolic metabolites known for their antioxidant, apoptotic, anti-cancer, anti-inflammatory, anti-bacterial, anti-viral, anti-fungal, and anti-protozoal properties. Though the genus includes more than 100 species, we have attempted to summarize the biological activities of the 34 lignans isolated from selected Mexican Bursera plants.

Chemical profile and pharmacological effects of the resin and essential oil from Bursera slechtendalii: A medicinal "copal tree" of southern Mexico.

This study reports on the volatile profile and pharmacological activities of the essential oil and resin from Bursera slechtendalii, an aromatic medicinal tree commercialized in southern Mexico. The essential oil contained 25 volatiles including p-cymen-8-ol (25.4-35.7%), n-hexyl hexanoate (6.8-17.6%) and n-octyl hexanoate (7.6-14.8%), whereas the crystallized resin contained 14 volatiles, including n-octyl acetate (29.6-34.2%), limonene (15.8-18.7%) and n-octyl butyrate (12.6-17-6%). The inhalation of vapors from the resin and essential oil caused a significant anxiolytic-like effect (p < .01) in ICR mice after 20 min of exposure at a dose of 50-150 mg L-1. The prolonged inhalation of the essential oil (for 40 days, for 15 min, twice a day) produced a significant decrease (p < .01) in total cholesterol and LDL-c content as well as an increase of HDL-c levels in the same murine model. Interestingly, levels of hepatic lipid hydroperoxide decreased, whereas the hepatic activity of superoxide dismutase and glutathione peroxidase was significantly enhanced (P < .05). The detection of p-cymen-8-ol and n-octyl acetate in the plasma of mice strongly suggests their bioavailability and possible role in the biological activities described herein. Also, both the resin and essential oil from B. slechtendalii, as well as their main volatiles, showed a potent repellence activity against Aedes aegypti (p < .01).

Bursera copallifera Extracts Have Cytotoxic and Migration-Inhibitory Effects in Breast Cancer Cell Lines.

Plants from the Bursera genus are widely distributed in the tropical dry forests of Mexico. In traditional medicine, extracts from different species of Bursera have been used for a wide range of biological activities, including the treatment of cancer-related symptoms. Compounds present in the Bursera genus include lignans, flavonoids, steroids, short-chain aliphatic alkanes, acetates, alcohols, ketones, and terpenoids. In some instances, secondary metabolites of these classes of compounds may induce cytotoxicity, and therefore we sought to investigate the effects of B. copallifera leaf extracts in breast cancer cell lines to evaluate their potential therapeutic value for the treatment of breast cancer, one of the most prevalent types of cancer in women worldwide. Two B. copallifera leaf extracts exerted cytotoxic effects on both the MCF7 and MDA-MB-231 breast cancer cell line models. The cytotoxic effect was more evident in the MDA-MB-231 triple negative cell line inhibiting also the migration of these cells. We identified hydroxycinnamic acid and flavonol derivatives as major phenolic components of the extracts. Our results strongly suggest a potential use of the Bursera leaf extracts rich in phenolic compounds, their individual phenolic compounds, or their combinations for the treatment of breast cancer.

Two new lignans from the resin of Bursera microphylla A. gray and their cytotoxic activity.

Two new lignans, namely 7-O-podophyllotoxinyl butyrate (1) and dihydroclusin 9-acetate (2), were isolated from the dichloromethane fraction of a methanol extract of Bursera microphylla (Burseraceae), along with eight known lignans (3-10). Their structures were determined by means of comprehensive spectroscopic analysis. Lignans 2-6 were tested for their anti-proliferative activity on the cancer cell lines LS180, A549 and HeLa, and on a non-cancer cell line, ARPE-19. Only compounds 4 and 5 showed an interesting activity on HeLa cells.

The Hexane Fraction of Bursera microphylla A. Gray Induces p21-Mediated Anti-Proliferative and Pro-Apoptotic Effects in Human Cancer-Derived Cell Lines.

Bursera microphylla (BM), one of the common elephant trees, is widely distributed in the Sonoran Desert in Mexico. The Seri ethnic group in the Sonoran Desert uses BM as an anti-inflammatory and painkiller drug for the treatment of sore throat, herpes labialis, abscessed tooth, and wound healing. Dried stems and leaves of BM are used in a tea to relieve painful urination and to stimulate bronchial secretion. Furthermore, BM is used for fighting venereal diseases. To investigate the effects of the hexane fraction of resin methanol extract (BM-H) on cell growth, the acute myeloid cell line (OCI-AML3) was treated with 250, 25, or 2.5 µg/mL of BM-H. The first 2 concentrations were able to significantly decrease OCI-AML3 cell number. This reduced cell number was associated with decreased S-phase, blockade of the G2/M phase of the cell cycle, and increased cell death. Similar results were obtained on all tested tumor cell lines of different origins. We found that blockade of the cell cycle was due to upregulation of p21 protein in a p53-independent way. Increase of p21 was possibly due to upstream upregulation of p-ERK (which stabilizes p21 protein) and downregulation of p-38 (which promotes its degradation). Regarding cell death, activation of caspase-3, but not of caspase-8 or -9, was detectable after BM-H treatment. In conclusion, these data suggest that the BM's hexane fraction inhibited proliferation of cell lines mainly by a p21-dependent, p53-independent mechanism and promoted apoptosis through activation of caspase-3, but not caspase-8 or -9.

Anti-Candida Activity of Bursera morelensis Ramirez Essential Oil and Two Compounds, α-Pinene and γ-Terpinene-An In Vitro Study.

The candidiasis caused by C. albicans is a public health problem. The abuse of antifungals has contributed to the development of resistance. B. morelensis has demonstrated antibacterial and antifungal activities. In this work the activity of the essential oil of B. morelensis was evaluated and for its two pure compounds with analysis of the different mechanisms of pathogenesis important for C. albicans. The essential oil was obtained by the hydro-distillation method and analyzed using GC-MS. The anti-Candida activity was compared between to essential oil, α-Pinene and γ-Terpinene. GC-MS of the essential oil demonstrated the presence of 13 compounds. The essential oil showed antifungal activity against four C. albicans strains. The most sensitive strain was C. albicans 14065 (MFC 2.0 mg/mL and MIC50 0.125 mg/mL) with α-Pinene and γ-Terpinene having MFCs of 4.0 and 16.0 mg/mL respectively. The essential oil inhibited the growth of the germ tube in 87.94% (8.0 mg/mL). Furthermore, it was observed that the essential oil diminishes the transcription of the gene INT1. This work provides evidence that confirms the anti-Candida activity of the B. morelensis essential oil and its effect on the growth of the germ tube and transcription of the gene INT1.

IN VIVO AND IN VITRO ANTILEISHMANIAL EFFECTS OF METHANOLIC EXTRACT FROM BARK OF BURSERA APTERA.

BACKGROUND: Cutaneous leishmaniasis lacks effective and well-tolerated treatments. The current therapies mainly rely on antimonial drugs that are inadequate because of their poor efficacy. Traditional medicine offers a complementary alternative for the treatment of various diseases. Additionally, several plants have shown success as anti-leishmanial agents. Therefore, we sought to evaluate the in vitro and in vivo activity of MEBA against Leishmania mexicana. MATERIALS AND METHODS: Methanolic extract of B. aptera was obtained by macetration, after we determined in vitro anti-leishmanial activity of MEBA by MTT assay and the induced apoptosis in promastigotes by flow cytometry. To analyze the in vivo anti-leishmanial activity, we used infected mice that were treated and not treated with MEBA and we determined the levels of cytokines using ELISA. The phytochemical properties were determined by CG-MS and DPPH assay. RESULTS: We determined of LC50 of 0.408 mg/mL of MEBA for in vitro anti-leishmanial activity. MEBA induced apoptosis in promastigotes (15.3% ± 0.86). Treated mice exhibited smaller lesions and contained significantly fewer parasites than did untreated mice; in addition, we found that IFN-γ and TNF-α increased in the sera of MEBA-treated mice. GC-MS analysis showed that podophyllotoxin was the most abundant compound. Evaluation of the activity by DPPH assay demonstrated an SC50 of 11.72 µg/mL. CONCLUSION: Based on the above data, it was concluded that MEBA is a good candidate in the search for new anti-leishmanial agents.

ANTIMICROBIAL ACTIVITY OF BURSERA MORELENSIS RAMÍREZ ESSENTIAL OIL.

BACKGROUND: Bursera morelensis, known as "Aceitillo", is an endemic tree of Mexico. Infusions made from the bark of this species have been used for the treatment of skin infections and for their wound healing properties. In this work, we present the results of a phytochemical and antimicrobial investigation of the essential oil of B. morelensis. MATERIALS AND METHODS: The essential oil was obtained by a steam distillation method and analyzed using GC-MS. The antibacterial and antifungal activities were evaluated. RESULTS: GC-MS of the essential oil demonstrated the presence of 28 compounds. The principal compound of the essential oil was a-Phellandrene (32.69%). The essential oil had antibacterial activity against Gram positive and negative strains. The most sensitive strains were S. pneumoniae, V. cholerae (cc) and E. coli (MIC 0.125 mg/mL, MBC 0.25 mg/mL). The essential oil was bactericidal for V. cholera (cc). The essential oil inhibited all the filamentous fungi. F. monilifome (IC50 = 2.27 mg/mL) was the most sensitive fungal strain. CONCLUSIONS: This work provides evidence that confirms the antimicrobial activity of the B. morelensis essential oil and this is a scientific support about of traditional uses of this species.

The Hexane Fraction of Bursera microphylla A Gray Induces p21-Mediated Antiproliferative and Proapoptotic Effects in Human Cancer-Derived Cell Lines.

Bursera microphylla (BM), one of the common elephant trees, is widely distributed in the Sonoran desert in Mexico. The Seri ethnic group in the Sonoran desert uses BM as an anti-inflammatory and painkiller drug for the treatment of sore throat, herpes labialis, abscessed tooth, and wound healing. Dried stems and leaves of BM are used in a tea to relieve painful urination and to stimulate bronchial secretion. Furthermore, BM is used for fighting venereal diseases. To investigate the effects of the hexane fraction of resin methanol extract (BM-H) on cell growth, the acute myeloid cell line (OCI-AML3) was treated with 250, 25, or 2.5 µg/mL of BM-H. The first 2 concentrations were able to significantly decrease OCI-AML3 cell number. This reduced cell number was associated with decreased S-phase, blockade of G2/M phase of the cell cycle, and increased cell death. Similar results were obtained on all tested tumor cell lines of different origins. We found that blockade of the cell cycle was a result of upregulation of p21 protein in a p53-independent way. Increase of p21 was possibly a result of upstream upregulation of p-ERK (which stabilizes p21 protein) and downregulation of p-38 (which promotes its degradation). Regarding cell death, activation of caspase-3, but not of caspase-8 or -9, was detectable after BM-H treatment. In conclusion, these data suggest that BM-H inhibited proliferation of cell lines mainly by a p21-dependent, p53-independent mechanism and promoted apoptosis through activation of caspase-3 but not caspase-8 or -9.

Actividad citotóxica de fracciones orgánicas de dos especies nativas de Guatemala (Bursera simaruba y Byrsonima crassifolia) con potencial actividad anticáncer identificada por estudios previos de tamizaje / Cytotoxic activity of organic fractions of two native species of Guatemala (Bursera simaruba and Byrsonima crassifolia) with potential anticancer activity identified by previous screening studies

El cáncer es un problema de salud importante a nivel mundial, especialmente en países de medianos y bajos ingresos (World Cancer Research Fund International, 2015a). En Guatemala se estimó una incidencia de 13,271 casos en el 2012 (excluyendo el cáncer de piel no melanoma) (Bray et al., 2013a). A pesar de que existen múltiples tratamientos farmacológicos, varios de ellos resultan inaccesibles por su costo elevado y limitada disponibilidad en países en desarrollo, además de que producen efectos adversos capaces de comprometer incluso la vida del paciente. En países megadiversos como Guatemala, resulta entonces prometedora la búsqueda de nuevos agentes terapéuticos de origen natural, más seguros y menos costosos que los quimioterapéuticos convencionales, capaces de atenuar la formación de un tumor y su crecimiento por procesos antiproliferativos y/o pro-apoptóticos (Auyeung & Ko, 2012). En el presente trabajo se evaluó la capacidad citotóxica de cuatro extractos orgánicos de las hojas y corteza de dos especies nativas de Guatemala, Bursera simaruba y Byrsonima crassifolia, cuyo potencial antitumoral ha sido previamente tamizado, habiéndose reportado que las fracciones acetónicas y metanólicas de la corteza son activas contra las líneas celulares de cáncer de cérvix (HeLa) y de mama (MCF-7) (Cates et al., 2013). Se realizó de cada órgano una extracción fraccionada con un gradiente de polaridad creciente (hexano, diclorometano, acetato de etilo y butanol). Su capacidad antitumoral se evaluó inicialmente mediante el bioensayo general de citotoxicidad en Artemia salina y posteriormente sobre células en cultivo de la línea de cáncer de mama MCF-7. Este ensayo de citotoxicidad se realizó por medio del método de tinción con sulforodamina B, en colaboración con la Dra. Cecilia Díaz, participante de RIBECANCER, en el Instituto Clodomiro Picado de la Universidad de Costa Rica. En el ensayo de Artemia salina no se encontró toxicidad en las fracciones orgánicas evaluadas (LD50 > 1 mg/mL), mientras que en el cultivo celular se determinó que únicamente la fracción hexánica de la corteza de B. simaruba fue citotóxica (IC50 = 14.057ug/mL) contra las células MCF-7. Así mismo, la fracción hexánica de la hoja de B. crassifolia y las fracciones orgánicas extraídas de ambos órganos de las dos especies vegetales con diclorometano, fueron moderadamente citotóxicas en el ensayo (20 ≤ IC50 ≤ 50 µg/mL). Sin embargo, debido a que ninguno de los extractos resultó altamente citotóxico (IC50 < 10ug/mL), de acuerdo a los criterios previamente establecidos en RIBECANCER, ninguno de ellos calificó para pasar a la siguiente fase del proyecto, en la que se evaluarían la IC100, su potencial genotóxico y se calcularía el índice de selectividad utilizando células normales como control. En cuanto a la determinación de la capacidad antioxidante de las fracciones orgánicas de las dos especies vegetales, se determinó en el tamizaje cualitativo primario realizado por cromatografía en capa fina que, de las 16 fracciones orgánicas, ocho presentaban actividad baja, dos tenían actividad moderada, cuatro tenían actividad fuerte y solamente dos presentaron actividad muy fuerte. Se estableció que la fracción con mayor capacidad antioxidante fue la extraída de la corteza de B. crassifolia con acetato de etilo, ya que se obtuvieron valores de 0.1040 +/- 0.0021 mg/mL con el método de DPPH micrométrico y 0.3217 +/- 0.0082 ug de ácido gálico/g con el de fenoles totales. Debido a que se ha demostrado que las líneas celulares tumorales pueden tener diferente sensibilidad a la acción tóxica de un mismo compuesto, deberá darse seguimiento al estudio de la bioactividad de los extractos evaluados contra otras líneas celulares tumorales. Además, se sugiere realizar investigaciones posteriores que permitan identificar las moléculas bioactivas en las fracciones que demostraron actividad citotóxica y antioxidante en el presente estudio.