Methods for interpolating missing data in aerobiological databases.

Missing data is a common problem in scientific research. The availability of extensive environmental time series is usually laborious and difficult, and sometimes unexpected failures are not detected until samples are processed. Consequently, environmental databases frequently have some gaps with missing data in it. Applying an interpolation method before starting the data analysis can be a good solution in order to complete this missing information. Nevertheless, there are several different approaches whose accuracy should be considered and compared. In this study, data from 6 aerobiological sampling stations were used as an example of environmental data series to assess the accuracy of different interpolation methods. For that, observed daily pollen/spore concentration data series were randomly removed, interpolated by using different methods and then, compared with the observed data to measure the errors produced. Different periods, gap sizes, interpolation methods and bioaerosols were considered in order to check their influence in the interpolation accuracy. The moving mean interpolation method obtained the highest success rate as average. By using this method, a success rate of the 70% was obtained when the risk classes used in the alert systems of the pollen information platforms were taken into account. In general, errors were mostly greater when there were high oscillations in the concentrations of biotic particles during consecutive days. That is the reason why the pre-peak and peak periods showed the highest interpolation errors. The errors were also higher when gaps longer than 5 days were considered. So, for completing long periods of missing data, it would be advisable to test other methodological approaches. A new Variation Index based on the behaviour of the pollen/spore season (measurement of the variability of the concentrations every 2 consecutive days) was elaborated, which allows to estimate the potential error before the interpolation is applied.

Increasing resolution of airborne pollen forecasting at a discrete sampled area in the southwest Mediterranean Basin.

Daily fluctuations of the airborne pollen concentrations produce variations on symptomatology in allergic population. Such fluctuations are influenced by local vegetal coverage, flowering phenology, geography and climatology. Since 1991, airborne pollen of Malaga province (southern Spain) has been monitored in 7 different locations. Malaga station has been kept operational uninterruptedly throughout the studied period, while the rest of the stations only worked in periods of 2-4 years. Weekly, its pollen information is updated online to inform the population in order to prevent allergic diseases. Increasing the spatial resolution of pollen information would be very useful for allergic population living at unsampled locations. Due to the impossibility of keeping operational a high number of pollen stations covering the whole province of Malaga, the aim of this study is to create spatial models to extrapolate and forecast the pollen concentrations to Malaga province by using the concentrations registered at the capital as unique input. To do so, the relationships obtained between the airborne pollen concentrations detected at Malaga city and those detected at the other stations have been used to elaborate models for the main pollen types registered at the province. These models were spatially interpolated all over the province by using co-kriging techniques and the Compensated Thermicity Index as covariable. As result of this work, pollen distribution of the 8 most prevalent taxa has been depicted all over the whole Malaga province and an allergy alert system has been set up to extrapolate pollen information from Malaga to the whole province.

A Pharmacological Update of Ellagic Acid.

Ellagic acid is a common metabolite present in many medicinal plants and vegetables. It is present either in free form or as part of more complex molecules (ellagitannins), which can be metabolized to liberate ellagic acid and several of its metabolites, including urolithins. While ellagic acid's antioxidant properties are doubtless responsible for many of its pharmacological activities, other mechanisms have also been implicated in its various effects, including its ability to reduce the lipidemic profile and lipid metabolism, alter pro-inflammatory mediators (tumor necrosis factor-α, interleukin-1ß, interleukin-6), and decrease the activity of nuclear factor-κB while increasing nuclear factor erythroid 2-related factor 2 expression. These events play an important role in ellagic acid's anti-atherogenic, anti-inflammatory, and neuroprotective effects. Several of these activities, together with the effect of ellagic acid on insulin, glycogen, phosphatases, aldose reductase, sorbitol accumulation, advanced glycation end-product formation, and resistin secretion, may explain its effects on metabolic syndrome and diabetes. In addition, results from recent research have increased the interest in ellagic acid, both as a potential protective agent of the liver and skin and as a potential anticancer agent, due to the specific mechanisms affecting cell proliferation, apoptosis, DNA damage, and angiogenesis and its aforementioned anti-inflammatory properties. Taken together, these effects make ellagic acid a highly interesting compound that may contribute to different aspects of health; however, more studies are needed, especially on the compound's pharmacokinetic profile. In this review, we selected papers published from 2005 to the present.

Pollen limitation may be a common Allee effect in marine hydrophilous plants: implications for decline and recovery in seagrasses.

Pollen limitation may be an important factor in accelerated decline of sparse or fragmented populations. Little is known whether hydrophilous plants (pollen transport by water) suffer from an Allee effect due to pollen limitation or not. Hydrophilous pollination is a typical trait of marine angiosperms or seagrasses. Although seagrass flowers usually have high pollen production, floral densities are highly variable. We evaluated pollen limitation for intertidal populations of the seagrass Zostera noltei in The Netherlands and found a significant positive relation between flowering spathe density and fruit-set, which was suboptimal at <1200 flowering spathes m(-2) (corresponding to <600 reproductive shoots m(-2)). A fragmented population had ≈35 % lower fruit-set at similar reproductive density than a continuous population. 75 % of all European populations studied over a large latitudinal gradient had flowering spathe densities below that required for optimal fruit-set, particularly in Southern countries. Literature review of the reproductive output of hydrophilous pollinated plants revealed that seed- or fruit-set of marine hydrophilous plants is generally low, as compared to hydrophilous freshwater and wind-pollinated plants. We conclude that pollen limitation as found in Z. noltei may be a common Allee effect for seagrasses, potentially accelerating decline and impairing recovery even after environmental conditions have improved substantially.

[Exclusive enteral nutrition continues to be first line therapy for pediatric Crohn's disease in the era of biologics]. / La nutrición enteral exclusiva continua siendo el tratamiento de primera línea en la enfermedad de Crohn pediátrica en la era de los biológicos.

INTRODUCTION: Exclusive enteral nutrition (EEN) has been to be more effective than corticosteroids in achieving mucosal healing without their side effects. OBJECTIVES: To determine the efficacy of EEN in terms of inducing clinical remission in newly diagnosed CD children and to study the efficacy of this therapeutic approach in improving the degree of intestinal mucosa inflammation. MATERIALS AND METHODS: The medical records of patients with newly diagnosed Crohn's disease treated with EEN were reviewed retrospectively. The degree of mucosal inflammation was assessed by fecal calprotectin (FC). Remission was defined as a PCDAI<10. RESULTS: Forty patients (24 males) were included, the age at diagnosis was 11.6 ± 3.6 years. Of the 34 patients who completed the EEN period, 32 (94% per-protocol analysis) achieved clinical remission. This percentage fell to 80% in the intention-to-treat analysis. The compliance rate was 95%. Duration of EEN was 6.42 weeks (IQR 6.0-8.14). FC was significantly higher in patients with moderate and severe disease. Median baseline FC levels (680 µg/g) decreased significantly to 218 µg/g (P<0.0001) after EEN. We found a statistically significant correlation between FC and PCDAI (rho=0.727; P<0.0001). Early use of thiopurines (< 8 weeks) versus subsequent use was not associated with improved outcomes during the follow-up. CONCLUSIONS: EEN administered for 6-8 weeks is effective for inducing clinical remission and decreasing the degree of mucosal inflammation. We did not find differences in terms of maintenance of remission in patients treated early with thiopurines.

Cacao, actualización de sus propiedades beneficiosas para la salud humana / Cocoa, an update of its beneficial properties for human health

Las semillas de cacao (Theobroma cacao L., Esterculiáceas) y sus derivados, además de su valor nutritivo, tienen un gran interés por sus propiedades farmacológicas. En su composición destacan tres grupos de principios: bases nitrogenadas, lípidos y compuestos fenólicos, principalmente catequinas y sus oligómeros, las proantocianidinas (de dímeros a decámeros). Los polifenoles del cacao poseen actividad antioxidante, reducen la oxidación del colesterol-LDL, incrementan los niveles de colesterol-HDL, reducen la glucemia basal y postprandial, incrementan la secreción de insulina y mejoran la sensibilidad a la misma. Todos estos efectos metabólicos, junto a la inhibición de la lipoxigenasa, incremento del óxido nítrico y la disminución de la agregación plaquetaria, le confieren propiedades protectoras cardiacas y vasculares. Además disminuye la síntesis de mediadores proinflamatorios e incrementa la de los antiinflamatorios e inhibe factores de transcripción implicados en la inflamación y carcinogénesis, lo que le confiere propiedades antiinflamatorias y quimiopreventivas del cáncer. También se han descrito un efecto neuroprotector (AU)

In addition to its nutritional value, Cocoa seeds (Theobroma cacao L., Sterculiaceae) and its derivatives also have a great interest due to its pharmacological properties. Three groups of constituents stand out: nitrogen bases, lipids and polyphenols, mainly catechins and their oligomers proanthocianidins (dimers to decamers). The phenolic compounds in cocoa have anti-oxidant properties, reduce LDL-cholesterol oxidation, increase HDL-cholesterol levels, reduce the basal and postprandial glycaemia, and increase the secretion of insulin, improving the sensibility to it. These metabolic effects, together with the inhibition of lipoxygenase, the increase of nitric oxide and the reduction of platelet aggregation, confer cocoa good vascular and cardiac protective properties. Moreover, these polyphenols decrease the synthesis of proinflammatory mediators and increase that of anti-inflammatory mediators. Furthermore, they inhibit transcription factors implicated in inflammation and carcinogenesis, conferring anti-inflammatory and cancer chemopreventive properties to cocoa. Its neuroprotective effects have also been reported (AU)

Shikonin promotes intestinal wound healing in vitro via induction of TGF-ß release in IEC-18 cells.

The intestinal barrier is a complex system with a dynamic structure that is designed for the maintenance of homeostasis in healthy individuals. Ulcerative colitis, one of the main manifestations of inflammatory bowel disease, is characterized by an inadequate and delayed wound healing. Shikonin, the active principle in the root of Lithospermum erythrorhizon, has demonstrated its ability to attenuate dextran sulfate sodium-induced ulcerative colitis in mice. Moreover, the root of L. erythrorhizon has been used in traditional Chinese medicine for treatment of burns, anal ulcers, hemorrhoids and skin wounds. However, the effect of shikonin on intestinal wound healing is unknown. Using an in vitro model for wound healing, we observed that shikonin enhances cell migration of intestinal epithelial cells through a mechanism that involves TGF-ß1 induction. The combination of shikonin's anti-inflammatory activity together with its wound-healing properties makes it a great potential therapeutic agent for the treatment of injury associated with intestinal inflammation.

Traditional chinese medicine remedy to jury: the pharmacological basis for the use of shikonin as an anticancer therapy.

Shikonin is the major constituent of the root of Lithospermum erythrorhizon, which has been used in traditional Chinese medicine to treat external wounds, burns, or dermatitis for centuries. Nowadays, this root is commonly used as an herbal medicine against cancer. Studies carried out over the past 30 years have demonstrated that many of the effects historically associated with the use of this root have a scientific basis, with shikonin and its derivatives being responsible for its pharmacological properties. These include both anti-inflammatory and anticancer effects. While previous summaries have focused on the pharmacokinetics and toxicity of shikonin, the aim of this review is to report on the most current findings with regard to shikonin's antitumor activity by summarizing and comparing the various studies published in the last ten years and discussing the pharmacological aspects that make shikonin a promising anticancer agent.

Anti-inflammatory agents from plants: progress and potential.

The identification of substances that can promote the resolution of inflammation in a way that is homeostatic, modulatory, efficient, and well-tolerated by the body is of fundamental importance. Traditional medicines have long provided front-line pharmacotherapy for many millions of people worldwide. Medicinal extracts are a rich source of therapeutic leads for the pharmaceutical industry. The use of medicinal plant therapies to treat chronic illness, including rheumatoid arthritis (RA) and inflammatory bowel disease (IBD), is thus widespread and on the rise.The aim of this review is to present recent progress in clinical anti-inflammatory studies of plant extracts and compound leads such as green tea polyphenols, curcumin, resveratrol, boswellic acid, and cucurbitacins, among others, against chronic inflammatory diseases, mainly RA and IBD. In this context, the present paper also highlights the most promising experimental data on those plant extracts and pure compounds active in animal models of the aforementioned diseases.

Inhibition of ulcerative colitis in mice after oral administration of a polyphenol-enriched cocoa extract is mediated by the inhibition of STAT1 and STAT3 phosphorylation in colon cells.

We studied a polyphenol-enriched cocoa extract (PCE) with epicatechin, procyanidin B2, catechin, and procyanidin B1 as the major phenolics for its anti-inflammatory properties against dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in mice. PCE reduced colon damage, with significant reductions in both the extent and the severity of the inflammation as well as in crypt damage and leukocyte infiltration in the mucosa. Analysis ex vivo showed clear decreases in the production of nitric oxide, cyclooxygenase-2, pSTAT-3, and pSTAT1α, with NF-κB p65 production being slightly reduced. Moreover, NF-κB activation was reduced in RAW 264.7 cells in vitro. In conclusion, the inhibitory effect of PCE on acute UC induced by DSS in mice was attenuated by oral administration of PCE obtained from cocoa. This effect is principally due to the inhibition of transcription factors STAT1 and STAT3 in intestinal cells, with NF-κB inhibition also being implicated.

Inhibition of transcription factors by plant-derived compounds and their implications in inflammation and cancer.

Inflammation is a general term used to describe various pathological processes with diverse causes that can include infection, trauma, or an autoimmune response. Due to its many causes, the inflammatory response involves multiple and varied mediators, including vasoactive amines, free radicals, and both lipidic and peptidic mediators. Medicinal plants and the compounds derived from them are a good source of new and specific inhibitors of the inflammatory process. The past decade has witnessed many important discoveries in this field, with new findings challenging the more traditional views of pharmacologists. Various studies, for example, have demonstrated the positive effects of plant-derived phenolics, which act as anti-oxidants, free radical scavengers, and inhibitors of nitric-oxide synthase, cyclooxygenase, and lipoxygenase. The anti-inflammatory activity of chalcones has been correlated with the induction of heme oxygenase-1 while phlorotannins have been found to inhibit matrix metalloproteinase, which is implicated in arthritis, chronic inflammation, and wrinkle formation. Sesquiterpene lactones have been studied as inhibitors of NF-kappaB activity and the relationship between their chemical structure and pharmacological activity has been clearly established. Recently, cucurbitacins have been described as inhibitors of JAK -STAT and NF-AT functions related to inflammation; they were also found to induce apoptosis of cells involved in the inflammatory response. This review focuses mainly on the effects of natural products on transcription factors, which are the most promising targets for designing new active drugs against inflammation and cancer.

Interaction of dicaffeoylquinic derivatives with peroxynitrite and other reactive nitrogen species.

Plant phenolic antioxidants, among them catechins and hydroxycinnamoyl conjugates, constitute a well defined class of inhibitors of reactive nitrogen species (RNS). To gain deeper insight in this field, we examined the effects of 3,5-di-O-caffeoylquinic acid (DCA), its methyl ester (DCE) and epigallocatechin gallate (EGCG) in nitrative and oxidative processes. These compounds were found to be strong inhibitors of the nitration of tyrosine residues induced by ONOO- in bovine seroalbumin, with their IC50 values (10-40 microM) notably decreasing in the presence of bicarbonate. When studied on the intracellular protein tyrosine nitration induced by ONOO- in cultured murine fibroblasts as well as that induced by phorbol ester (PMA) in nitrite-supplemented human neutrophils, all three phenolics were also effective (100% and over 75% inhibition for fibroblasts and neutrophils, respectively, at 25 microM). This ability seems to be due to a direct interaction with ONOO- or with the species generated by leukocytes. The possible interference with the production of NO was also studied: both DCA and EGCG inhibited nitrite production in LPS-stimulated macrophages by 24% and 40%, respectively, and the expression of nitric oxide synthase-2 (NOS-2), as well. DCA and EGCG reduced by 52% and 59%, respectively, the NF-kappaB transcriptional activity. In contrast, DCE did not show any effect. The assayed phenolics exert varying degrees of protection against the chemical modifications induced by RNS depending not only on the hydroxyl pattern, but also on the presence of bicarbonate.

In vitro and in vivo effects of Ranunculus peltatus subsp. baudotii methanol extract on models of eicosanoid production and contact dermatitis.

Ranunculus (Crowfoot) species are numerous and they are all reputed to be counter-irritants and are used in several topical conditions. In order to study the pharmacological mechanisms of action underlying this popular use, a methanol extract of Ranunculus peltatus was tested in vitro in various assays involving eicosanoid and human elastase release by intact cells as well as in vivo, with models of delayed-type hypersensitivity (DTH) contact dermatitis. The extract proved to be a selective inhibitor of the cyclooxygenase-1 pathway, producing the total inhibition of 12-(S)-HHTrE release at 200 microg/mL, while leaving both 5-lipoxygenase and 12-lipoxygenase activities unaffected at the same dose. The n-hexane, chloroform and ethyl acetate fractions of the crude methanol extract inhibited LTB(4) release by intact rat peritoneal neutrophils, but more polar fractions were inactive and did not increase the 5-LOX activity as seen previously for extracts of other Ranunculus species. In the in vivo models, the methanol extract reduced the dinitrofluorobenzene (DNFB)-induced oedema by 40%, but failed to inhibit the oedema brought on by oxazolone. The results agree with the age-old assertion that Water Crowfoot species can be used as a topical antiinflammatory remedy without the prominent irritant action that accompanies the application of non-aquatic Ranunculus species.

[Efficacy of exclusive enteral feeding as primary therapy for paediatric Crohn's disease]. / Eficacia del tratamiento nutricional primario en la enfermedad de Crohn pediátrica.

INTRODUCTION: The primary nutritional therapy (PNT), which consists in the administration of exclusive enteral formula feeds (polymeric, semi-elemental or elemental formula) for a period of no less than 6-8 weeks, has proven to be effective in inducing clinical remission in children with Crohn's disease. The clinical remission does not always include histological remission or cure of the mucosa. Faecal calprotectin is closely correlated with endoscopic and histological findings but is slightly associated with clinical activity scores. PATIENTS AND METHODS: An observational prospective study including all patients under 14 years of age diagnosed with Crohn's disease between January 2002 and October 2007, and who were fed exclusively with polymeric formula (Modulen IBD, Nestle, Vevey, Switzerland) during the onset of the disease. Clinical controls were carried out (weight, height, body mass index [BMI) and the Paediatric Crohn's Disease Activity Index [PCDAI)) and faecal calprotectin was measured at the beginning and at weeks 4 and 8 of treatment. The clinical remission was defined as having a PCDAI less than or equal to 10. Faecal calprotectin values below 50 microg/g faeces were considered as normal. RESULTS: There were 14 patients (9 males), mean age at diagnosis of 10.74 +/- 2.56 years. At week 4, 71 % of patients (10/14) had achieved clinical remission and a decrease in faecal calprotectin levels that was not significant. After 8 weeks, 85 % of our patients were in clinical remission and faecal calprotectin values had declined significantly without reaching normal levels. CONCLUSION: Primary nutritional therapy administered over a period of 8 weeks is capable of inducing clinical remission and improving the degree of inflammation of the intestinal mucosa.

Demethylnobiletin inhibits delayed-type hypersensitivity reactions, human lymphocyte proliferation and cytokine production.

BACKGROUND AND PURPOSE: Our aim was to examine the effect of demethylnobiletin on various experimental models of delayed-type hypersensitivity (DTH) reactions and to determine its influence on the mediators and enzymes involved in these reactions. EXPERIMENTAL APPROACH: DTH was induced in mice by oxazolone, dinitrofluorobenzene (DNFB) and sheep red blood cells (SRBC). The effect of demethylnobiletin on the ensuing DTH was studied, especially in relation to oedema formation, cell infiltration and tissue damage. Its activity on different mediators implicated in DTH reactions was also determined and its effect on nitric oxide synthase (NOS)-2 analysed. Finally, its influence on T lymphocyte proliferation, apoptosis and caspase 3 activity was tested. KEY RESULTS: DTH reactions were all reduced by demethylnobiletin. The experimental results suggest that the compound may act by reducing cell infiltration and by suppressing mediators such as interleukin-2 (IC50=1.63 microM), interleukin-4 (IC50=2.76 microM), tumour necrosis factor-alpha (IC50=0.66 microM), interferon-gamma (IC50=1.35 microM), and interleukin-1 beta (46% at 2.5 microM) and by concomitantly increasing the production of the anti-inflammatory cytokine, interleukin-10. In addition, while demethylnobiletin affected nitric oxide production, it did not modify NOS-2 expression. Finally, demethylnobiletin inhibited proliferation of T cells and induced their apoptosis. CONCLUSIONS AND IMPLICATIONS: Demethylnobiletin decreased DTH reactions induced by various agents. This finding, along with the fact that the compound has a low toxicity and exhibits several other interesting properties, could pave the way for other structurally related citroflavonoids to be used as pharmacological agents in complementary therapies.

Protein tyrosine nitration induced by heme/hydrogen peroxide: inhibitory effect of hydroxycinnamoyl conjugates.

The present study was designed to optimize the experimental conditions that govern the heme-catalyzed nitration of protein tyrosine residues by nitrite, and, within this framework, to study the effects of 3,5-dicaffeoylquinic acid and its methyl ester, both of which have been previously reported to be antioxidants and inhibitors of leukocyte functions. Although the presence of hydrogen peroxide is essential in cell-free systems, an excess of this compound was found to be detrimental, so much so that an increase in hemin concentration actually resulted in an inverse effect on the reaction, depending on the levels of fixed hydrogen peroxide. Unlike previous reports on nitrite-induced albumin tyrosine nitration, the optimal pH here was found to be 7.0. The two caffeoyl conjugates tested were found to be effective inhibitors of protein nitration, with IC50 values ranging from 20 - 30 microM, regardless of the presence of bicarbonate. For the inhibition of myeloperoxidase-catalyzed protein nitration by human polymorphonuclear leukocytes stimulated by phorbol ester, the potencies obtained were up to two times higher. This is the first time that caffeoylquinic esters have been reported as inhibitors of heme-based protein nitration.

Inhibition of the pro-inflammatory mediators' production and anti-inflammatory effect of the iridoid scrovalentinoside.

We have studied scrovalentinoside, an iridoid with anti-inflammatory properties isolated from Scrophularia auriculata ssp. pseudoauriculata, as an anti-inflammatory agent in different experimental models of delayed-type hypersensitivity. We found that scrovalentinoside reduced the edema induced by oxazolone at 0.5 mg/ear and sheep red blood cells at 10 mg/kg. The observed effect occurred during the last phase or inflammatory response; during the earlier phase or induction of the delayed-type hypersensitivity reaction, no significant activity was noted. Thus, scrovalentinoside reduced both the edema and cell infiltration in vivo and reduced lymphocyte proliferation in vitro, affecting the cycle principally during the first 48 h. Whereas cells stimulated with phytohemagglutinin changed from the G(0)/G(1) phase to the S and G(2)/M phases, when these same cells were treated with scrovalentinoside (100 microM), they remained in the G(0)/G(1) phase. Finally, scrovalentinoside inhibited the production of the pro-inflammatory mediators' TNF-alpha, IFN-gamma, IL-1beta, IL-2, IL-4, LTB(4), and NO, but had no effect on the production of the anti-inflammatory cytokine IL-10.

Anti-inflammatory activity of 5-O-demethylnobiletin, a polymethoxyflavone isolated from Sideritis tragoriganum.

We have studied the effect of 5- O-demethylnobiletin ( 1) on both the inflammation of mouse ears induced by repeated application of 12- O-tetradecanoylphorbol 13-acetate (TPA) and the acute mouse paw oedemas induced by carrageenan and phospholipase A (2) (PLA (2)), and determined its activity on 5-lipoxygenase (5-LOX) and elastase release/activity. Compound 1 reduced the oedema formation, cell infiltration, and tissue damage in the inflammation induced by TPA in mouse ears, along with the acute oedema induced by carrageenan in mouse paws and the acute PLA (2)-induced oedema in mouse paws. The flavone inhibited leukotriene B (4) formation in rat neutrophils and elastase release in human neutrophils, but did not reduce the expression of cyclooxygenase-2 (COX-2) in murine RAW 264.7 macrophages. These experimental results suggest that 1 may act through a direct inhibition of 5-LOX, without affecting the expression of COX-2.

Medicinal plants and antimicrobial activity.

In the present paper, we analyze the past, present and future of medicinal plants, both as potential antimicrobial crude drugs as well as a source for natural compounds that act as new anti-infection agents. In the past few decades, the search for new anti-infection agents has occupied many research groups in the field of ethnopharmacology. When we reviewed the number of articles published on the antimicrobial activity of medicinal plants in PubMed during the period between 1966 and 1994, we found 115; however, in the following decade between 1995 and 2004, this number more than doubled to 307. In the studies themselves one finds a wide range of criteria. Many focus on determining the antimicrobial activity of plant extracts found in folk medicine, essential oils or isolated compounds such as alkaloids, flavonoids, sesquiterpene lactones, diterpenes, triterpenes or naphtoquinones, among others. Some of these compounds were isolated or obtained by bio-guided isolation after previously detecting antimicrobial activity on the part of the plant. A second block of studies focuses on the natural flora of a specific region or country; the third relevant group of papers is made up of specific studies of the activity of a plant or principle against a concrete pathological microorganism. Some general considerations must be established for the study of the antimicrobial activity of plant extracts, essential oils and the compounds isolated from them. Of utmost relevance is the definition of common parameters, such as plant material, techniques employed, growth medium and microorganisms tested.