Venezuelan Andes Research Articles

Chemical composition and cytotoxic activity of the essential oil of Hinterubera imbricata species collected in Venezuelan Andes

Hinterhubera imbricata Cuatrec. et Aristeg belongs to Asteraceae family and it is one of the six endemic species that grows in Venezuela Andean. Present investigation aimed to determine the chemical composition of the essential oil of Hinterhubera imbricata and to evaluate the cytotoxic activity in human tumor cell lines from MCF-7 (breast carcinoma without over-expression of the HER2/cerb-2), PANC-1 (pancreatic adenocarcinoma ductal type) and SKBr3 (breast carcinoma, in which the HER2/cerb-2 gene is overexpressed). Results indicated that essential oil was mainly composed of monoterpenes being α-phellandrene, α-pinene, β-phellandrene and p-cymene as major components. Cytotoxic analysis revealed that this essential oil exhibited antitumor activity in all human tumor lines tested being more cytotoxic for the pancreatic cancer tumor line. To the best of our knowledge there are no published studies regarding either the genus Hinterhubera or the species Hinterhubera imbricata, thus, present investigation is considered as a contribution to the genus Hinterhubera study.

Diversity, structure and dynamics of tropical montane forests: Insights from permanent-plot monitoring in the Venezuelan Andes

Diversity, structure and dynamics of tropical montane forests: Insights from permanent-plot monitoring in the Venezuelan Andes

Intraspecific variation in pollination ecology due to altitudinal environmental heterogeneity.

Plant-pollinator interactions are constrained by floral traits and available pollinators, both of which can vary across environmental gradients, with consequences for the stability of the interaction. Here, we quantified how the pollination ecology of a high-mountain hummingbird-pollinated plant changes across a progressively more stressful environmental gradient of the Venezuelan Andes. We compared pollination ecology between two populations of this plant: Piedras Blancas (PB) and Gavidia (GV), 4450 and 3600 m asl, respectively. We hypothesised that self-compatibility might be higher at the higher altitude site, however we found that flowers showed similar capacities for self-compatibility in both localities. Seed production by flowers exposed to natural pollinators was significantly higher in the lower locality, where we also found higher nectar quality, larger flowers and increased frequencies of pollinator visitations. Interestingly, the population energy offered in the nectar was the same for both localities due to the higher density and floral aggregation found in the higher altitude population. Our study demonstrates how two plant populations in different environmental conditions have different pollination ecology strategies. Pollinator visitations or their absence result in trait associations in one population that are independent in the other. These population differences are not explained by differences in pollinator assembly, but by environmental heterogeneity.

Use of dynamic simulation and Forrester diagrams to describe the growth of lettuce (Lactuca sativa L.) under field conditions

The use of computational tools to describe some processes of crop growth has evolved in recent decades and remains an area of active research, where more and more applications are incorporated with the integration of a greater number of mathematical tools, statistics, and computational calculation efficiency, simplifying the tasks of modeling and visualizing the components of the system used. Current research proposes a dynamic growth model for lettuce cultivation using Forrester diagrams to evaluate different scenarios involving five growth functions and five lettuce cultivars in field conditions of the Bailadores region (Venezuelan Andes, 2550 m a.s.l.). The lettuce variety Coastal Star achieved the greatest accumulation of dry matter used as a response in each model. The logistics of growth function was properly adjusted to the experimental data compared to the other models. The proposed diagram model can be used as a basis for the construction of more complex models that incorporate other physiological variables of the crop and the growth environment.

INTERESANTE REGISTRO, CON IMPLICACIONES CONSERVACIONISTAS, LLENA UN VACÍO EN EL RANGO DE DISTRIBUCIÓN GEOGRÁFICA PARA Hyloscirtus platydactylus (HYLIDAE)

Hyloscirtus platydactylus is reported for the first time from the Rangel municipality of Merida state, in the Venezuelan Andes. It also constitutes the first record of this taxon for the Montane dry forest Life Zone and the highest elevation record for the species. Twenty-eight post-metamorphic specimens and a dozen tadpoles were located during the local rainy season through visual searches in small springs surrounded by vegetation in intermediate stages of ecological succession. The new record is important because it fills a gap in the species' distribution and presents evidence of its presence in an area with different ecological characteristics than the other areas where it was already known. This discovery of H. platydactylus is of singular importance for the conservation of the natural vegetation patches that remain in this Venezuelan Andean region, which are important in terms of the representation of its characteristic fauna and flora. Hyloscirtus platydactylus largely lacks ecological and biological information and is classified as Vulnerable (VU) in the IUCN red list of species.

A new dwarf gecko of the genus Pseudogonatodes (Squamata: Sphaerodactylidae) from the eastern slope of the Andean Cordillera de Mrida in northern South America.

Pseudogonatodes is a poorly known genus of small bodied, diurnal, ground-dwelling geckos widely distributed in northern South America. No additional species have been described in over two decades. Herein we describe a new species from the eastern slope of the Cordillera de Mrida in the Venezuelan Andes. The new species is readily diagnosable morphologically from the other seven recognized species of Pseudogonatodes by having a single postnasal scalea putative autapomorphy. Furthermore, it is characterized by a unique combination of phenotypic characters that includes granular dorsal scales, three large postrostrals, five to six loreals, mental U-shaped, four to six postmentals, 2629 ventrals between anterior levels of fore- and hind limbs, third lamella under fourth toe not distinctly enlarged, and subcaudal pattern 11. In addition to characterizing the external morphology, we present a description of the skull, based on 3D digital models reconstructed from high resolution computed microtomography scans. The discovery of this new species highlights the still underestimated diversity of this group of Neotropical dwarf geckos and underscores the need for further studies on its systematics and taxonomy.

Integrative taxonomy led to recognising Clusia reginae (Clusiaceae), a new tree species from the Venezuelan Andes

SummaryClusia reginae (Clusiaceae) is described using an integrative taxonomy approach. Field observations, discriminant analyses of morphological characters and phylogenetic inference based on molecular data led to the recognition of a new species of tree. This new taxon is distinct for having broadly obovate leaves, white petals, bright yellow flower resin and relatively large fruits. Clusia reginae is known from the foothills and valleys of the Venezuelan Andes and is here assessed using IUCN criteria as Vulnerable.

Chemical Composition and Antibacterial activity of Essential Oils from Fruits of Vismia baccifera and Vismia macrophylla Collected at different Locations in Venezuelan Andes

Background: Genus Vismia (Hipericaceae/Clusiaceae) is distributed mainly in tropical and subtropical areas of Central America and South America although some species have been reported in Africa as well. Species of this genus have been used in traditional medicine to alleviate different ailments such as skin infections, to treat urinary tract disorders, as antirrheumatic, antipyretic, among others. Previous investigations have revealed that species from Vismia genus are composed mainly of terpenes, anthrones, lignans, flavonoids, anthraquinones, steroids and xanthones. The purpose of the investigation was to determine the chemical composition and antimicrobial activity of essential oils from the fruits of V. baccifera and V. macrophylla collected in Venezuelan Andes. Methods: Vimia species were collected at different locations in Mérida and Táchira state, Venezuela. Essential oils were obtained through Hidrodistilation and chemical compositon was performed by GC and GC/MS techniques. Antimicrobial analysis was carried out by disc diffusion assays. Results: GC and GC/MS analysis showed that these species are mainly composed of sesquiterpenes being α-curcumene, β-curcumene, germacrene D, γ-bisabolene and β-caryophyllene among the major components. Antimicrobial activity was also performed with species under investigation. Results showed a broad spectrum of activity since both species were able to inhibit not only Gram- positive (Stpahylococcus aureus, Enterococcus faecalis) and Gram-negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa) but yeast (Candida albicans and Candida krusei) as well. Conclusions: According to the results observed in the investigation, Vismia species might be considered as an alternative to aid infectious diseases.

Sustainable Valorization of Organic Materials as Substrates for Soilless Crops in Protected Environments in the Venezuelan Andes

Agricultural production activities generate a large amount of waste, most of which is of organic origin from plant remains. These residues could easily be transformed into a resource, specifically, into a substrate for use in soilless cultivation; however, in most cases, they are not used. Therefore, a characterization of local agricultural residues was carried out to determine their use as a substrate for crop cultivation without soil in a protected environment. The selected substrates were Sphagnum peat, coir fiber, and compost, which were managed alone or in mixtures of 50/50, 75/25, or 25/75% v/v ratios. We also included a mixture of virgin mountain soil and earthworm humus (known as INIA mixture) because it is used by local growers. The results showed that the substrates based on coir fiber, peat, and mixtures of both presented suitable characteristics for horticultural crops. On the contrary, compost-based substrates had high pH values and low organic matter contents that could be improved before use. The relationship found between the evaluated parameters of each substrate allowed us to establish that variables, such as the content of organic matter and water at different tensions and particle sizes, can be utilized to make a quick selection of the substrates produced locally, which would lead to the use of waste in a way that is more consistent with sustainable agricultural production and minimal environmental impact, by being used in the production of crops in containers without soil. In addition, these results can be used as an alternative reference in localities where these residues are easily available.

Morpho‐Tectonics of Transpressional Systems: Insights From Analog Modeling

AbstractTranspressional margins are widespread, and their dynamics are relevant for plate boundary evolution globally. Though transpressional orogen evolution involves a topographic response to deformation, many studies focus only on the structural development of the system ignoring surface processes. Here, we present a new set of analog models constructed to investigate how tectonic and surface processes interact at transpressive plate boundaries and shape topography. Experiments are conducted by deforming a previously benchmarked crustal analog material in a meter‐scale plexiglass box while controlling erosion through misting nozzles mounted along the transpressional wedge. To analyze the experiments, we generate digital elevation models from laser scans and conduct image correlation analysis on photos taken during experiments. We focus on three experiments that cover a range of erosional conditions and shortening stages (two end‐member erosion models and a dry reference). In all experiments, a bivergent wedge forms, and strain partitioning broadly evolves according to previously established models. Regarding drainage networks, we find that the streams in our models develop differently through feedback between fault development and drainage rearrangement processes. Differences between end‐member erosional models can be explained by the varying response of streams to structure modulated by rainfall. Additionally, erosion may influence the structural evolution of transpressional topography, leading to accelerated strike‐slip partitioning. From these results, we create a model for developing structures, streams, and topography where incision and valley formation along main structures localize exhumation. We apply insights from the models to natural transpressional systems, including the Transverse Ranges, CA, and the Venezuelan Andes.

Life history notes on the Spot-fronted (Cypseloides cherriei), Chestnut-collared (Streptoprocne rutila), and White-collared (S. zonaris) swifts in the Andes of Venezuela

Life history notes on the Spot-fronted (Cypseloides cherriei), Chestnut-collared (Streptoprocne rutila), and White-collared (S. zonaris) swifts in the Andes of Venezuela

REE + Y signatures of the Navay phosphate deposit, SW Venezuela: Seawater paleoredox conditions and diagenetic implications

Phosphate rock occurrences in western Venezuela are well-known in Cretaceous sedimentary sequences, which are associated to the Caribbean-Tethyan passive margin, along an SW-trend belt of the Venezuelan Andes chain. In this study, the geochemical characteristics of the Navay phosphate deposit were investigated to discuss the ocean paleo-oceanographic conditions and diagenetic controls that prevailed during the deposit formation. The rare earth elements plus yttrium (REY) concentrations were determined and normalized with the Post-Archean Australian Shale (PAAS) values to generate the REY patterns. Our results reveal a typical seawater signature, except for the absence of a marked negative Ce* anomaly (Ce/Ce* = 0.76–1.00). The determined seawater REY patterns, along to the calculated ratios for (La/Sm)N = 0.78–1.00, and (La/Yb)N = 0.34–0.66, are similar to the modern oceanic water ratios. These data point to a lack of diagenetic alteration on the primary REY signatures, which corresponds with a terrigenous-free marine sediment source for the REY content present in the deposit. In brief: i) the slightly negative anomalies displayed by the Ce* and Eu*, accompanied by the Mn depletion, ii) a relative enrichment of some transition metal elements (V, Cr, and Cu), and iii) the low Mo/U ratios, are all of them considered as geochemical indicators of suboxic to anoxic conditions, which were predominated during the phosphogenetic processes of the deposit. Furthermore, our data reveals an economic potential of the phosphorites as a raw material to produce phosphoric acid (H3PO4) as well as a source of supply for rare earth elements, by means of: i) relative high grades of P2O5 (15.46–30.09 wt %), ii) low CaO/P2O5 ratios (1.22–1.28), iii) a lack of organic matter, chert or chalcedony, iv) a low content of Mg (0.07–0.22%), v) REE concentrations varying from 141.82 to 256.53 μg/g, with an average value of 208.14 μg/g; and vi) concentrations for toxic elements (i.e., V, Cr, Co, Ni, Cu, Zn, As, Sr, Pb, and U) below or at the acceptable levels, in comparison to commercial phosphorites worldwide.

Identification of Eroded and Erosion Risk Areas Using Remote Sensing and GIS in the Quebrada Seca watershed

The aim of this research was to identify eroded areas and areas at risk of erosion (EAER) as indicators of soil degradation by water erosion in a semiarid watershed of the Venezuelan Andes in 2017. To this effect, remote sensing techniques and geographic information systems (GIS) were used, focusing on spectral reflectance data from a satellite image, given the absence of continuous pluviographic information and data on soil properties in developing countries. This methodology involved estimating the potential water erosion risk (PWER) and mapping eroded and erosion risk areas (EAER) based on calculating the spectral Euclidean distance to bare soils and a remote sensing technique, which was selected via linear regression. Receiver operating characteristics (ROC) curves were determined to define classification thresholds, which were validated by means of a supervised classification and associated to PWER values. The main results indicate that EAER1 identified more eroded areas with bare soils (229,77 ha) as opposed to EAER2 (195,57 ha). Similarly, it was evident that the first alternative was more successful that the second (sum of the first three principal components). The PWER analysis, in addition to the erosion mapping developed and other data and criteria, such as mini-mum area size of interest, could help to consider necessary soil conservation measures.

Mio Pliocene sedimentation and its impact on the petroleum history of the Táchira Depression, Venezuela

Even though the first oil field of Venezuela (La petrólia, 1883) was discovered in the Táchira Depression, located at the junction of the Venezuelan Andes with the Cordillera Oriental of Colombia, no liquid hydrocarbon discoveries have been made in the area ever since. However, there are extensive asphalt accumulations impregnating Mio-Pliocene conglomerates, which have been exploited intermittently mostly for road construction. These asphalt accumulations occur in the central eastern portion of the Táchira Depression in the basal part of fluvial conglomerates of the La Copé Fm. that were deposited uncomfortably on top of Cenozoic and Cretaceous rocks. These sediments were sourced and deposited unconformably on the nose and flanks of a large-scale anticline oriented N40° and plunging to the SW (Uribante High) product of the first phase of the Andean orogeny. The conglomerates located on the western part of this high were charged with oil derived from the Cretaceous La Luna Formation that was generating at the time of deposition of the unit. This oil migrated into the conglomerates and moved updip until they became trapped in a major stratigraphic accumulation. The seals of the accumulation were formed by lateral facies changes, overbank shales, or eventually the muddier Upper Member of the La Copé Fm. It is postulated that this stratigraphic trap was later deformed, uplifted and partially eroded, with the asphalt impregnations being the remnants of this paleo-accumulation and not present-day oil seeps as previously postulated.A rough estimate of the total hydrocarbons in place in the outcrops of the La Copé Fm is in the order of 100 MMBO, however the original accumulation was orders of magnitude larger. Since the bridged regional high was the focus of charge in the basin during the peak of oil generation in the Táchira Depression, it is believed that a large portion of the hydrocarbons generated were lost, which may explain the lack of significant discoveries in the area.

Eight new species of lichenized Basidiomycota in the genera Acantholichen, Cyphellostereum and Dictyonema s.str. (Agaricales, Hygrophoraceae) from northern South America

A study of Acantholichen P.M. Jørgensen, Cyphellostereum D.A. Reid and Dictyonema s.str. C. Agardh ex Kunth from the Venezuelan Andes (Sierra Nevada de Mérida) and the Guayana Highlands (Alto Orinoco) revealed the presence of eight species new to science, viz., Acantholichen dendroideus V. Marcano, Cyphellostereum mucuyense V. Marcano, Dictyonema andinum V. Marcano, D. duidense V. Marcano, D. laurae V. Marcano, D. subinvolutum V. Marcano, D. subsericeum V. Marcano and D. umbricola V. Marcano. Acantholichen dendroideus grows on mosses in shady and humid disturbed forest and is characterized by densely and dichotomously branched microsquamules, with a pruinose surface and large acanthohyphidia. Cyphellostereum mucuyense grows on mosses and sandy soils, lacks a jigsaw-puzzle-shaped hyphal sheath and prothallus, the fibrils are not penetrated by tubular fungal hyphae and the basidiocarp surface is finely arachnoid. This is the first record of Cyphellostereum in Venezuela. Dictyonema andinum might be confused with D. irrigatum (Berkeley & M. A. Curtis) Lücking from the Andaman Islands, but differs in the broader and ascending fibrils, a thicker photobiont layer and hypothallus, as well as the formation of stereoid-corticioid hymenophores. Dictyonema duidense from the Guayana Highlands and D. subsericeum from the Venezuelan Andes belong in the group of shelf-like morphotypes, with a semicircular thallus resembling D. sericeum s.str. Dictyonema duidense grows on tree trunks and is characterized by thick, very broad lobes and an areolate, rugose surface and it lacks clamp connections whereas D. subsericeum grows on tree branches and is characterized by variability of color (white, greenish blue, brown), size and shape (semicircular to hemispherical), filamentous lobes, a hirsute surface, fibrillose margins, clamp connections on the hyphae, cyphelloid hymenophores resembling attachment hapters, and very small, globose to subglobose basidiospores. Dictyonema laurae resembles D. subsericeum but is characterized by a continuous greenish blue crust-like thallus with an irregular surface, with discontinuous, fibrillose, and narrow margins projecting and ascending from the substrate, a hapteriform hymenophore, and its lacks clamp connections on the hyphae. Dictyonema subinvolutum is characterized by a jigsaw-puzzle-shaped hyphal sheath, fibrils penetrated by tubular fungal hyphae, and a smooth, pruinose, resupinate hymenophore. Finally, D. umbricola grows on mosses in very shady habitats and produces a corticioid hymenophore raised from the thallus, resembling apothecial discs, jigsaw-puzzle-shaped cells around the filaments and a distinct, discontinuous, white prothallus. Of the eight species of Dictyonema s.lat. registered from Venezuela, seven are known only from the Venezuelan Andes (A. dendroideus, C. mucuyense, D. andinum, D. laurae, D. subsericeum, D. subinvolutum, D. umbricola) and one is known only from the Venezuelan Amazonas (D. duidense). The high concentration of Acantholichen, Cyphellostereum and Dictyonema species in tropical America and especially of the latter genus in the Venezuelan Andes indicates that this region constitutes an important centre for speciation and endemism of Dictyonema clade/subtribe Dictyonematinae.

Seismotectonics of Shallow-Focus Earthquakes in Venezuela with Links to Gravity Anomalies and Geologic Heterogeneity Mapped by a GMT Scripting Language

This paper presents a cartographic framework based on algorithms of GMT codes for mapping seismically active areas in Venezuela. The data included raster grids from GEBCO, EGM-2008, and vector geological layers from the USGS. The data were iteratively processed in the console of GMT, converted by GDAL, formatted, and mapped for geophysical data visualisation; the QGIS was applied for geological mapping. We analyzed 2000 samples of the earthquake events obtained from the IRIS seismic database with a 25-year time span (1997–2021) in order to map the seismicity. The approach to linking geological, topographic, and geophysical data using GMT scripts aimed to map correlations among the geophysical phenomena, tectonic processes, geological setting, seismicity, and earthquakes. The practical application of the GMT scripts consists in automated mapping for the visualization of geological risks and hazards in the mountainous region of the Venezuelan Andes. The proposed method integrates the approach of GMT scripts with state-of-the-art GIS techniques, which demonstrated its effectiveness as a tool for mapping spatial datasets and rapid data processing in an iterative regime. In this context, using GMT and GIS to find similarities between the regional earthquake distribution and the geological and topographic setting is essential for hazard risk assessment. This study can serve as a basis for predictive seismic analysis in geologically vulnerable regions of Venezuela. In addition to a technical demonstration of GMT algorithms, this study also contributes to geological and geophysical mapping and seismic hazard assessments in South America. We present the full scripts used for mapping in a GitHub repository.

Patterns in climate and seedling establishment at a dry tropical treeline

In some internal valleys of the northern Andes, precipitation at treeline elevation is seasonal, with one or two dry periods that could exert a strong control on tree seedling survival. However, little is known about (1) the severity of the dry periods, due to a lack of climate data, or (2) the effect of drought on tree seedling demographic dynamics and how this is modulated by local plant interactions in these tropical-alpine ecosystems. We studied annual precipitation variation and seedling demography and ecophysiology in relation to microclimate and neighboring plants in a dry treeline ecotone at 3100 m a.s.l in the Venezuelan Andes. We selected seedlings of the dominant tree species Cybianthus marginatus and Clusia multiflora at three sites, each with three adjacent 10 × 10-m plots within the forest, forest border, and páramo. For both species, seedling density was zero in the páramo and did not differ between border and forest. Growth rates were low for both species, but higher for Cybianthus in the border than in the forest. Survival rates were high in both environments. Low assimilation and transpiration rates were found in both species regardless of the environment. The spatial association of seedlings with moisture-regulating elements such as mosses, ferns and basal rosettes may indicate a benefit of better hydric conditions in their neighborhood. Our study shows a strong limitation for tree establishment in the páramo, but high rates of survival at the edge of the forest. This suggests a scenario of slow potential forest expansion at this tropical treeline, tree cover advancing in a closed front by the successive formation of forest-edge vegetation allowing tree seedling establishment outside of the forest.

Stolonicaulon: A Section-Puzzle within Marsupella (Gymnomitriaceae, Marchantiophyta).

Marsupella sect. Stolonicaulon is not speciose and is a commonly neglected section within the genus, which currently includes three species with somewhat similar morphologies (wiry shoots with distanced leaves) and distributions in the mountains of tropical and subtropical regions (SE (Southeast) Asia, the Venezuelan Andes, and the high mountains of SE Brazil). After studying materials that were found to be dissimilar to the “traditional” Marsupella that were collected in the last decade by the authors of this article, it was found that these plants belong to three new-for-science species, and all of these species should be included in Marsupella sect. Stolonicaulon. The newly described species have expanded the boundaries of morphological variability, not only for the section itself, but also for the genus based on two findings: (1) the leaves of Marsupella sect. Stolonicaulon can be either appressed and entire or spaced and deeply divided (thus, the plants could occasionally be similar to Cephaloziella or Anastrophyllum); (2) some species of the section possess regular underleaf production. The first discovery of regular underleaves in Marsupella, as noted in two of the three newly described taxa, is the main morphological novelty described in this paper. The development of regular underleaves is a presumable relict character that brings Marsupella closer to Nardia, which was recently transferred to the Gymnomitriaceae and occupies an isolated position within its own subfamily, Nardioideae.

Understanding institutional changes in irrigation management: a comparative case study of two communities in the Venezuelan Andes

ABSTRACT This paper explores institutional changes in two water users’ associations (WUAs) in the Venezuelan Andes. The methodology is based on ethnographic work. The results show that both WUAs have modified the rule systems in irrigation management to respond to economic, institutional and environmental changes. They have implemented a better organization of water sharing, adopted more efficient irrigation technologies, restored infrastructure and preserved high-altitude wetlands. The comparative approach adopted allowed us to show not only the similar factors that promoted institutional change, such as social capital, but also the differences related to the characteristics of the resource.

Antimycobacterial activity of acetone extract and isolated metabolites from folklore medicinal lichen Usnea laevis Nyl. against drug-sensitive and multidrug-resistant tuberculosis strains

Ethnopharmacological relevanceTuberculosis (Tb) is one of the most infectious diseases caused by Mycobacterium tuberculosis (M.t) with almost 2 million deaths yearly. Although many Tb control programs have been organised, there is an elevated number of Tb cases due to the appearance of extremely drug-resistant and multidrug-resistant (MDR) Tb strains. In the cultures of Venezuelan Andes, fruticose lichen Usnea laevis Nyl. (Usneaceae) with folklore name ‘Barba de Piedra, Tusinya’ is used as a natural remedy for Tb. Aim of the studyThis study was performed to provide a scientific rationale for the folklore usage of U. laevis in treating Tb by validating its antimycobacterial activity against two drug-sensitive and four MDR-Tb strains. Materials and methodsThe mycobacterial inhibitory activities of acetone extract (Ul), fractions (F1-10), and isolated metabolites (1–4) of U. laevis were evaluated against M.t H37Ra using 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide reduction menadione assay (XRMA). Furthermore, Ul and 1–4 were subjected to antimycobacterial activity against M.t H37Ra, Mycobacterium smegmatis, and four MDR-Tb (MDR-A8, MDR-V791, MDR-R and MDR-40) strains using resazurin microtitre plate assay (REMA) and cytotoxicity against THP-1 macrophages using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and their selectivity index values were also calculated. ResultsInitially, Ul has shown prominent inhibitory activity (IC50 value: 5.44 ± 0.36 μg/ml) and four of its fractions (F1, F2, F5 and F7) also exhibited the best inhibitory activity (IC50 values ranged from 7.46 ± 0.19 to 71.38 ± 2.57 μg/ml) against M.t H37Ra using XRMA. Purification of these bioactive fractions identified four metabolites, namely usnic acid (1), atranorin (2), salazinic acid (3), and lobaric acid (4). From the MIC values of REMA, it was identified that Ul, 1 and 4 were more effective in inhibiting the growth of all four MDR-Tb strains, compared to first-line drug rifampicin. Interestingly, Ul has shown better antimycobacterial activity than 1–4 and rifampicin against MDR-Tb strains may be due to the synergistic effect of its metabolites. Also, the IC50 values of Ul and 1–4 on THP-1 macrophages were found to be far higher than MIC values against tested Tb strains, indicating that THP-1 macrophages were not harmfully affected at concentrations that were effective against Tb strains. Further, the calculated selectivity index values revealed the more active and non-toxicity of Ul, 1 and 4 against MDR-Tb strains than rifampicin. ConclusionsThe current study lends the first evidence for the presence of antimycobacterial metabolites in U. laevis. The results exposed the Andean folklore use of U. laevis for treating Tb, and the key biomarker metabolites were found to be 1 and 4. Hence, it can be concluded that U. laevis can be used as a potential source for the novel drug development for MDR-Tb.