The in vitro rumen exsheathment test for studying the effect of plant extracts on the exsheathment of Haemonchus contortus infective larvae.

This study applied the in vitro rumen exsheathment test (IVRET) to evaluate the exsheathment kinetics of Haemonchus contortus infective larvae (L3) incubated in ruminal liquor (RL) containing acetone:water extracts of Acacia pennatula (AP), Gymnopodium floribundum (GF), Havardia albicans (HA) or Lysiloma latisiliquum (LL). The role of polyphenols in the biological activity of the evaluated extracts was also determined. Larvae were incubated in RL either alone or added with a different plant extract (AP, GF, HA, or LL) at 1200 µg/mL. Polyethylene glycol (PEG) was added to block polyphenols in each treatment (RL+PEG, AP+PEG, GF+PEG, HA+PEG, and LL+PEG). After incubation times of 0, 1, 3, 6, 9, and 24 h, the exsheathment process was stopped to count the number of ensheathed and exsheathed L3. A Log-Logistic model was used to determine the L3 exsheathment kinetics in the different RL treatments. The inflection point of the respective kinetic curves, which indicates the time to reach 50 % exsheathed L3 (T50), was the only parameter that differed when comparing the exsheathment models (99 % probability of difference). The T50 values obtained for GF, HA, and LL treatments (T50 = 7.11 - 7.58 h) were higher in comparison to the T50 of RL (5.72 h) (≥ 70 % probability of difference). The L3 incubated in RL added with GF, HA, and LL extracts delayed their exsheathment at 3 and 6 h of incubation (28.71 - 48.06 % exsheathment reduction) compared to the RL treatment. The T50 value for AP, AP+PEG, GF+PEG, HA+PEG, and LL+PEG were similar to RL and RL+PEG (T50 = 5.34 - 6.97 h). In conclusion, the IVRET can be used to identify plants with the potential to delay the exsheathment of H. contortus L3 in the ruminal liquor. The acetone:water extracts of G. floribundum, H. albicans, and L. latisiliquum delayed the T50 of H. contortus exsheathment, which was evident at 3 and 6 h of incubation in ruminal liquor. The observed exsheathment delay was attributed to the polyphenol content of the extracts.

Adapting the in vitro rumen incubation method to evaluate the effect of a plant extract on the exsheathment inhibition of Haemonchus contortus infective larvae.

This study adapted the in vitro rumen incubation (IVRI) method to evaluate the biological activity of a Gymnopodium floribundum leaves extract against the exsheathment of Haemonchus contortus infective larvae (L3), and to determine the role of plant polyphenols on the biological activity. The incubation protocol followed the IVRI method, adding polyethylene glycol (PEG) as a polyphenol-blocking agent. The L3 were incubated in ruminal liquor (RL), ruminal liquor with PEG (RL+PEG), ruminal liquor with G. floribundum extract (RLE), and ruminal liquor with G. floribundum extract and PEG (RLE+PEG). Incubation condition controls included phosphate buffered saline (PBS), PBS with PEG (PBS+PEG), incubation medium (without ruminal liquor) (IM), and incubation medium with PEG (IM+PEG). The L3 were recovered after incubation times of 0, 1, 3, 6, 9, and 24 h (39 °C). The respective L3 exsheathment kinetics were estimated for the different treatments (RL, RL+PEG, RLE, and RLE+PEG) using Log-Logistic models. The parameters of the different models were compared to determine the impact of the extract, with or without PEG, on the L3 exsheathment kinetics. The exsheathment in PBS and PBS+PEG remained < 2.71% at each incubation time. The exsheathment in IM and IM+PEG reached 13.58% and 17.18% at 24 h, respectively. The exsheathment percentages for RLE were lower than those for RL at 3, 6 and 9 h of incubation. The inflection point, indicating the time required to reach 50% of the maximal exsheathment (T50), was the only parameter that differed between the ruminal liquor models. The T50 in RLE (7.106 h) was higher than the values obtained for RL (5.385 h) and RL+PEG (4.923 h) (99.99% probability of being different). Such delay resulted in a reduction of exsheathment in RLE of 62% at 3 h, 38% at 6 h, and 12% at 9 h, relative to RL values. When PEG was added with the extract (RLE+PEG), the T50 (5.045 h) was similar to that of RL and RL+PEG. The IVRI method was adapted as an in vitro rumen exsheathment test (IVRET). The IVRET showed that H. contortus L3 exposed to G. floribundum extract delayed their exsheathment kinetics at different time points. The exsheathment delay was attributed to the polyphenol content of the extract.

Quinones as Promising Compounds against Respiratory Viruses: A Review.

Respiratory viruses represent a world public health problem, giving rise to annual seasonal epidemics and several pandemics caused by some of these viruses, including the COVID-19 pandemic caused by the novel SARS-CoV-2, which continues to date. Some antiviral drugs have been licensed for the treatment of influenza, but they cause side effects and lead to resistant viral strains. Likewise, aerosolized ribavirin is the only drug approved for the therapy of infections by the respiratory syncytial virus, but it possesses various limitations. On the other hand, no specific drugs are licensed to treat other viral respiratory diseases. In this sense, natural products and their derivatives have appeared as promising alternatives in searching for new compounds with antiviral activity. Besides their chemical properties, quinones have demonstrated interesting biological activities, including activity against respiratory viruses. This review summarizes the activity against respiratory viruses and their molecular targets by the different types of quinones (both natural and synthetic). Thus, the present work offers a general overview of the importance of quinones as an option for the future pharmacological treatment of viral respiratory infections, subject to additional studies that support their effectiveness and safety.

An in vitro rumen incubation method to study exsheathment kinetics of Haemonchus contortus third-stage infective larvae.

This study developed and evaluated an in vitro rumen incubation (IVRI) method to describe the exsheathment kinetics of Haemonchus contortus third-stage infective larvae (L3) in ruminal liquor (RL). The specific objectives were (i) to standardize the IVRI method to facilitate the contact between L3 and RL as well as the larval recovery, and (ii) to apply the IVRI method to describe the exsheathment kinetics of H. contortus and to select the best fitting nonlinear model. Incubation devices containing H. contortus larvae were incubated according to the IVRI technique in cattle RL or PBS. The incubation conditions included RL mixed with a nitrogen-rich media, maintained at 39 °C, with pH = 7.0, vented with CO2 and manual agitation. The larvae were recovered after 0, 1, 3, 6, 9, 12, and 24 h. The exsheathed and ensheathed larvae were counted to estimate the exsheathment (%) in RL or PBS. Exsheathment in RL was analyzed with nonlinear regression models: Exponential, Gompertz, Logistic, Log-Logistic, and Weibull. The models' fit was compared to select the one that best described the exsheathment kinetics. The exsheathment in RL reached 6.52%, 20.65%, 58.22%, 69.24%, 73.08%, and 77.20% in 1, 3, 6, 9, 12, and 24 h, respectively. Although the Gompertz, Weibull, and Logistic models were adequate to describe the observed exsheathment, the Log-Logistic model had the best fit. The IVRI method using bovine RL represents a suitable tool for the study of the in vitro exsheathment kinetics of H. contortus L3.

Bioassay-Guided Fractionation of Erythrostemon yucatanensis (Greenm.) Gagnon & GP Lewis Components with Anti-hemagglutinin Binding Activity against Influenza A/H1N1 Virus.

Erythrostemon yucatanensis (Greenm.) Gagnon & GP Lewis is a legume tree native to and widely distributed in southeast Mexico, where its branches are used in traditional medicine. An in vitro evaluation of the antiviral activity of extracts and fractions from the leaves, stem bark and roots against two strains of the AH1N1 influenza virus was performed, leading to the identification of bioactive compounds in this medicinal plant. In a cytopathic effect reduction assay, the fractions from the leaves and stem bark were the active elements at the co-treatment level. These were further fractionated based on their hemagglutination inhibition activity. The analysis of spectroscopy data identified a combination of phytosterols (ß-sitosterol, stigmasterol and campesterol) in the stem bark active fraction as the main anti-hemagglutinin binding components, while 5-hydroxy-2(2-hydroxy-3,4,5-trimethoxyphenyl)-7-metoxi-4H(chromen-4-ona), which was isolated from the leaf extracts, showed a weak inhibition of viral hemagglutinin. Time of addition experiments demonstrated that the mixture of sterols had a direct effect on viral particle infectivity at the co-treatment level (IC50 = 3.125 µg/mL). This effect was also observed in the virus plaque formation inhibition assay, where the mixture showed 90% inhibition in the first 20 min of co-treatment at the same concentration. Additionally, it was found using qRT-PCR that the NP copy number was reduced by 92.85% after 60 min of co-treatment. These results are the first report of components with anti-hemagglutinin binding activity in the genus Erythrostemon sp.

Diospyros anisandra phytochemical analysis and anti-hemagglutinin-neuraminidase activity on influenza AH1N1pdm09 virus.

Influenza viral proteins Haemagglutinin (HA) and Neuraminidase (NA) are important targets for antiviral design. We analyzed for the first time the anti-HA activity and the NA inhibitory activity of extracts and their fractions from Diospyros anisandra on the influenza AH1N1pdm09 virus. The n-hexane fruit extract exhibited HA inhibitory (HAI) activity, and fraction F3 inhibited the hemagglutination from 12.5 up to 100 µg/ml. Gas chromatography-mass spectrometry analysis (GC-MS) on fraction F3, and the n-hexane fruit extract, identified six compounds that were individually evaluated. Only vitamin E and lupeol showed a slight inhibitory activity on HA at 100 µg/ml. Regarding the NA assays, the presence of fluorescent (coumarin) and antioxidant (α-tocopherol) compounds in the root extract, masked the NA assays when using fluorescence techniques. We concluded that D. anisandra is a promising source of bioactive compounds with diverse properties including anti-HA activity on the influenza AH1N1pdm09 virus.

Anthelmintic Activity of Extracts and Active Compounds From Diospyros anisandra on Ancylostoma caninum, Haemonchus placei and Cyathostomins.

The present study aimed to evaluate the anthelmintic activity of leaf and bark extracts of Diospyros anisandra collected during different seasons and their major constituents on eggs of Ancylostoma caninum, Haemonchus placei, and cyathostomins. Specifically, the eclosion inhibition of the methanolic extracts of the leaves and bark of D. anisandra collected during the dry and rainy seasons (600-37.5 µg/ml) were evaluated in addition to the fractions, sub-fractions (300-37.5 µg/ml) and active major constituents (150-2.3 µg/ml). The rainy season bark extract had the highest percentage of eclosion inhibition (PEI) against the evaluated nematodes (≥ 90% at 75 µg/ml) along with high ovicidal activity (90.0 to 93.4% at 75 µg/ml). The purification of the rainy season bark extract showed that its biological activity came from the non-polar n-hexane fraction (≥ 93% at 75 µg/ml). The bioguided fractionation pointed to sub-fraction 5 as having the highest anthelmintic activity against the three evaluated genera of nematodes (PEI ≥ 93% at 37.5 µg/ml). Gas chromatography and mass spectrometry revealed that the major constituent in sub-fraction 5 was plumbagin. Upon evaluation, plumbagin was confirmed to be responsible for the anthelmintic activity of D. anisandra, with a PEI ≥ 90% at 2.3 µg/ml on the three evaluated nematodes. Additionally, the compounds betulin and lupeol in the bark of D. anisandra were evaluated but presented low anthelmintic activity (PEI ≤ 5.3% at 2.3 µg/ml). In conclusion, the rainy season bark extract of D. anisandra exerts a high ovicidal activity against the eggs of the three studied nematodes. Plumbagin is the active compound responsible for this activity and represents a potential alternative for the control of different genera of gastrointestinal nematodes given the current scenario of anthelmintic resistance.

Antitubercular Activity of the Fungus Gliocladium sp. MR41 Strain.

Tuberculosis (TB) is a leading cause of death worldwide from infectious diseases and its inadequate treatment has led to emergence of resistant strains. The emergence of these strains renders the search for new drugs for the treatment of TB. The aim of this study was the evaluation of the anti-TB activity of the extract from fungus Gliocladium sp. MR41, and bioassay-guided fractionation and identification of majority compounds was carried out. Fungal strain culture was lyophilized and extracted by maceration in Ethyl Acetate (EtOAc). This extract was fractionated by liquid-liquid partitioning and chromatographic techniques, and the compounds were identified by their spectroscopic data. Furthermore, the EtOAc extract, fractions, and pure compounds were tested on Mycobacterium tuberculosis using the Microplate Alamar Blue Assay. From the bioactive AcetoNitrile Fraction (AcNF; MIC = 3.13 µg/mL) of the EtOAc extract, four compounds were isolated: ergosterol (1), ergosterol-5, 8-peroxide (2), 1, 6-di-O-acetyl-2,3,4,5-tetrahydroxy-hexane (3), and allitol (4). Only 2 exhibited potent activities against M. tuberculosis (MIC = 0.78 µg/mL). Additionally, this is the first report, to our knowledge, of polyols 3 and 4 from this fungus.

Bio-guided fractionation to identify Senegalia gaumeri leaf extract compounds with anthelmintic activity against Haemonchus contortus eggs and larvae.

Small ruminants browsing in tropical forests readily consume the foliage of Senegalia gaumeri. A S. gaumeri methanol:water extract was recently shown to have ovicidal activity against Haemonchus contortus eggs in vitro. In the present study, the fraction of a S. gaumeri methanol:water extract with ovicidal activity against H. contortus eggs and the metabolites potentially involved in this activity were identified. Bio-guided fractionation of the S. gaumeri methanol:water extract identified high ovicidal activity (80.29%, EC50 = 58.9 µg/mL) in the non-polar sub-fraction P1. Gas chromatography-mass spectrometry (GC-MS) identified several fatty acids: pentacosane (18.05%), heneicosane (18.05%), triacontane (30.94%), octacosane (18.05%), and hexanedioic acid bis-(2-ethylhexyl) ester (32.72%). Purification of the polar components of sub-fraction P1 led to the identification of p-coumaric acid as a major constituent. In egg hatch tests, 400 µg/mL p-coumaric acid resulted in an ovicidal effect of 8.7%, a larvae failing eclosion effect of 2.9%, and of the emerged larvae (88.4%), many were damaged. In conclusion, the low AH activity of p-coumaric acid against H. contortus eggs indicates that it is not solely responsible for the ovicidal activity of sub-fraction P1 but might act in synergy with other compounds in this fraction. However, p-coumaric acid showed potential anthelmintic effects against the larval stage of H. contortus.

Evaluation of cinnamic acid and six analogues against eggs and larvae of Haemonchus contortus.

This study evaluated the in vitro anthelmintic (AH) activity of cinnamic acid and six analogues against eggs and larvae of Haemonchus contortus. Stock solutions of each compound (trans-cinnamic acid, p-coumaric acid, caffeic acid, trans-ferulic acid, trans-sinapic acid, 3,4-dimethoxycinnamic acid, and chlorogenic acid) were prepared in PBS:Tween-20 (1%) for use in the egg hatch test (EHT) and larval exsheathment inhibition test (LEIT) at different concentrations (25-400 µg/mL). The respective effective concentration 50% (EC50) values with 95% confidence intervals were estimated. Mixtures made of all cinnamic acid and its analogues as well as some selected individual compounds were also tested in the EHT. Only ferulic and chlorogenic acids showed AH activity in the EHT (EC50: 245.2 µg/mL (1.26 mM) and 520.8 µg/mL (1.47 mM), respectively) (P < 0.05). A higher EC50 (1628.10 µg/mL) of the mixture of cinnamic acid and its analogues was required to observe activity against eggs mostly blocking the larvae hatching. The analogues' mixtures tested were less active than ferulic or chlorogenic acid alone. The activity of ferulic and chlorogenic acids against eggs was associated with larvae failing to hatch, and the two compounds exhibited antagonistic effects when evaluated together. All standards had an EC50 lower than 0.42 mM in the LEIT. Caffeic acid had the best activity in the LEIT (EC50 0.04 mM), followed by ferulic acid (EC50 0.11 mM) (P < 0.05). There was no clear, definitive structure-activity relationship for these non-flavonoid polyphenols against eggs or larvae of H. contortus in vitro. This study is the first to directly evaluate cinnamic acid and its derivatives as active compounds against eggs and larvae of H. contortus.

Pentacyclic triterpenes and other constituents in propolis extract from Melipona beecheii collected in Yucatan, México

ABSTRACT Thirteen pentacyclic triterpenes, methyl 3-oxours-12-en-23-oate, marsformosanone, taraxerone, β-amyrenone, α-amyrenone, lupenone, 24-methylencycloartan-3-one, moretenol acetate, β-amyrin acetate, germanicol acetate, 24-methylencycloartanyl acetate, β-amyrin, and α-amyrin were identified in a chloroform-methanol propolis extract from Melipona beecheii. Additionally, were identified in this propolis, hexadecanoic acid, methyl ester, octadecanoic acid, methyl ester and 1-triacontanol. The purification of the propolis extract was carried out using different chromatographic techniques, including vacuum liquid chromatography, gravity column chromatography and gel filtration chromatography Sephadex LH-20. The identification of the metabolites was performed using mass spectrometry.

Zeylanone epoxide isolated from Diospyros anisandra stem bark inhibits influenza virus in vitro.

Influenza virus infection is a public health problem, causing significant morbidity and mortality. Currently, zanamivir and oseltamivir are in common use, and there are already reports of antiviral resistance. Several studies have shown the antiviral potential of a wide variety of plant-based natural compounds, among them those of the quinone type. In this study, we evaluated the antiviral activity of naphthoquinones isolated from the stem bark of Diospyros anisandra, and we selected zeylanone epoxide (ZEP) to study its effects on influenza A and B viruses. Our results indicated that ZEP inhibits the replication of influenza A and B viruses, at early and middle stages of the replication cycle. Confined nuclear localization of the viral NP indicated that ZEP affects its intracellular distribution and reduces viral yield. This is the first report on the antiviral properties and possible mechanism of action of ZEP in vitro, showing its broad-spectrum activity against influenza A and B viruses.

Ecological Strategies Behind the Selection of Cultivable Actinomycete Strains from the Yucatan Peninsula for the Discovery of Secondary Metabolites with Antibiotic Activity.

The quest for novel natural products has recently focused on the marine environment as a source for novel microorganisms. Although isolation of marine-derived actinomycete strains is now common, understanding their distribution in the oceans and their adaptation to this environment can be helpful in the selection of isolates for further novel secondary metabolite discovery. This study explores the taxonomic diversity of marine-derived actinomycetes from distinct environments in the coastal areas of the Yucatan Peninsula and their adaptation to the marine environment as a first step towards novel natural product discovery. The use of simple ecological principles, for example, phylogenetic relatedness to previously characterized actinomycetes or seawater requirements for growth, to recognize isolates with adaptations to the ocean in an effort to select for marine-derived actinomycete to be used for further chemical studies. Marine microbial environments are an important source of novel bioactive natural products and, together with methods such as genome mining for detection of strains with biotechnological potential, ecological strategies can bring useful insights in the selection and identification of marine-derived actinomycetes for novel natural product discovery.

In vitro evaluation of anthraquinones from Aloe vera (Aloe barbadensis Miller) roots and several derivatives against strains of influenza virus.

Aloe vera is a crop of wide economic value of worldwide distribution, and a rich source of quinone components. Recently, antiviral aloe anthraquinones had been reported against human influenza virus. In the present work two anthraquinones, aloesaponarin-I (1) and aloesaponarin-II (2) were isolated from A. vera roots, and six derivatives were obtained by methylation (3), acetylation (4) and O-glycosyl (5-6) reactions starting from (1). Additionally, a new Tetra-O-acetyl-ß-d-glucopyranosyl derivative from 2 was also prepared. All compounds were evaluated against two strains of influenza virus AH1N1 by cytopathic effect reduction assay (CPE). The antiviral activity was determined by the ability of compounds to inhibit virus replication on Madin Darby Canine Kidney cells (MDCK). New derivatives 3-(2´,3´,4´,6´-Tetra-O-acetyl-ß-d-glucopyranosyl-aloesaponarin-I (5) and 3-(2´,3´,4´,6´-Tetra-O-acetyl-ß-d-glucopyranosyl- aloesaponarin-II (7) showed a cytopathic reduction effect against influenza strain A/Yucatán/2370/09 with IC50 of 30.77 and 13.70 µM, and against the virus A/Mexico/InDRE797/10 with IC50 of 62.28 and 19.47 µM, respectively. To assess the effect of derivatives 5 and 7 during one cycle of replication (0-10 h), a time-of-addition experiment was performed. As a result it was found that both compounds were most effective when added 6-10 h post-infection and significantly inhibited viral titre (> 70%) at the concentrations of 50 and 100 µM. Based on the structural analysis of the compounds, it was suggested that the Tetra-O-acetyl-ß-d-glucopyranosyl substituent at the C3 position of the anthraquinone might have an effect against the influenza AH1N1 virus.

Acaricidal activity of Havardia albicans and Caesalpinia gaumeri methanolic leaf extracts on Rhipicephalus microplus and its toxicity to laboratory animals.

The acaricidal activity of methanolic extracts from the leaves of Havardia albicans (Kunth Britton and Rose) and Caesalpinia gaumeri (Greenm) were tested on the larvae and adults of the cattle tick Rhipicephalus microplus Canestrini using the larval immersion test and the adult immersion test, respectively. The toxicity of these extracts was also evaluated on laboratory animals using toxicity bioassays at different concentrations: skin irritability (500 mg/ml), acute oral toxicity (5000 mg/kg), ocular irritability (1000 mg/ml) and dermal toxicity (5000 mg/kg). The acaricidal activity of the H. albicans extracts on R. microplus larvae showed a LC50 of 7.0% (4.3-11.4) and a LC99 of 25.5% (14.26-201.5). The acaricidal activity of the C. gaumeri extracts on larvae showed a LC50 of 7.8% (5.74-10.65) and a LC99 of 38.32% (22.22-146.48). The H. albicans extracts showed moderate acaricidal activity in the inhibition of egg laying (54.4 ± 12.4) and the inhibition of larval hatching (48.7 ± 6.8) in R. microplus adults. The C. gaumeri extracts also showed moderate acaricidal activity in the inhibition of egg laying (51.0 ± 11.2). However, none of the evaluated extracts showed significant toxicity on laboratory rodents. These plants show the potential to control R. microplus and could be administered topically or orally in animals. Further studies are needed to identify the active compound(s) and to evaluate the effects of these plants on R. microplus in vivo.

Naphthoquinones isolated from Diospyros anisandra exhibit potent activity against pan-resistant first-line drugs Mycobacterium tuberculosis strains.

BACKGROUND AND OBJECTIVES: The recent emergence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and totally drug-resistant (TDR) Mycobacterium tuberculosis (MTB) strains have further complicated the control of tuberculosis (TB). There is an urgent need of new molecules candidates to be developed as novel, active, and less toxic anti-tuberculosis (anti-TB) drugs. Medicinal plants have been an excellent source of leads for the development of drugs, particularly as anti-infective agents. In previous studies, the non-polar extract of Diospyros anisandra showed potent anti-TB activity, and three monomeric and five dimeric naphthoquinones have been obtained. In this study, we performed bioguided chemical fractionation and the isolation of eight naphthoquinones from D. anisandra and their evaluation of anti-TB and cytotoxic activities against mammalian cells. METHODS: The n-hexane crude extract from the stem bark of the plant was obtained by maceration and liquid-liquid fractionation. The isolation of naphthoquinones was carried out by chromatographic methods and identified by gas chromatography and mass spectroscopy data analysis. Anti-TB activity was evaluated against two strains of MTB (H37Rv) susceptible to all five first-line anti-TB drugs and a clinical isolate that is resistant to these medications (pan-resistant, CIBIN 99) by measuring the minimal inhibitory concentration (MIC). Cytotoxicity of naphthoquinones was estimated against two mammalian cells, Vero line and primary cultures of human peripheral blood mononuclear (PBMC) cells, and their selectivity index (SI) was determined. RESULTS: Plumbagin and its dimers maritinone and 3,3'-biplumbagin showed the strongest activity against both MTB strains (MIC = 1.56-3.33 µg/mL). The bioactivity of maritinone and 3,3'-biplumbagin were 32 times more potent than rifampicin against the pan-resistant strain, and both dimers showed to be non-toxic against PBMC and Vero cells. The SI of maritinone and 3,3'-biplumbagin on Vero cells was 74.34 and 194.11 against sensitive and pan-resistant MTB strains, respectively. CONCLUSION: Maritinone and 3,3'-biplumbagin possess a very interesting potential for development as new drugs against M. tuberculosis, mainly resistant profile strains.

Insecticidal effects of plant extracts on immature whitefly Bemisia tabaci Genn. (Hemiptera: Aleyroideae)

Background: The whitefly (Bemisia tabaci Genn.) is a widely distributed and highly harmful plant pest species. The management of B. tabaci has been typically carried out by chemical pesticides. In the last decade however, there has been an increasing interest in natural products, particularly those of plant origin, to control this pest species. In the present work, aqueous and ethanolic extracts of native plants from the flora of the Yucatán peninsula (Acalypha gaumeri, Annona squamosa, Carlowrightia myriantha, Petiveria alliaceae and Trichilia arborea) and the introduced plant Azadirachta indica were collected and evaluated for insecticidal activity against eggs and nymphs Bemisia tabaci. Results: Most of the aqueous and ethanolic extracts showed high insecticidal effects on B. tabaci eggs. The lowest LC50 values were recorded in the aqueous extracts of A. gaumeri (0.39% w/v), A. squamosa (0.36% w/v), P. alliaceae (0.42% w/v) and A. indica (0.30% /v), as well as in the ethanolic extracts of P. alliaceae (2.09 mg mL-1) and T. arborea (2.14 mg mL-1). On the other hand, B. tabaci nymphs were not affected by the aqueous extracts, but were highly sensitive to the ethanolic extracts of the tested plants. The lowest LC50 values were recorded in the ethanolic extracts of P. alliaceae (1.27 mg ml-1) and T. arborea (1.61 mg mL-1). The GC-MS analysis showed that phytol was the major component of the ethanolic extract of P. alliaceae and fatty acids were the major components of ethanolic extract of T. arborea. Conclusions: Overall, results suggest that ethanolic extracts of P. alliaceae and T. arborea leaves showed the highest insecticidal effects on eggs and nymphs B. tabaci. The extracts from P. alliaceae and T. arborea are good candidates to be developed as sources of natural insecticides for the management of immature B. tabaci since their effects were comparable with that showed by the extracts of A. indica, a well-known plant species for its insecticidal activity.

Antiprotozoal and cytotoxic studies on some isocordoin derivatives.

Isocordoin (1) and 2',4'-dihydroxy-3'-(gamma,gamma-dimethylallyl)-dihydrochalcone (7), chalcones isolated from the root of Lonchocarpus xuul, together with six analogues of 1 were tested in vitro against promastigotes of Leishmania mexicana and epimastigotes of Trypanosoma cruzi. Additionally, cytotoxic studies with MDCK cells were carried out using the MTT method. Among these derivatives, 2',4'-diacetoxy-3'-(3-methylbut-2-enyl)-chalcone (2) and 2',4'-dimethoxy-3'-(3-methylbut-2-enyl)-chalcone (3) showed the strongest antiprotozoal activity and lower cytotoxicity in comparison with isocordoin at a concentration in the microM range. Derivative 3 had the strongest trypanocidal activity with IC(50) values lower than those of nifurtimox and benznidazole, the common drugs used against these parasites. The selectivity index calculated for 3 (SI 109.3) confirms the selective trypanocidal activity of this metabolite.

Antimicrobial activity of Diospyros anisandra.

Leaves, root and stem bark of Diospyros anisandra were screened against two strains of Mycobacterium tuberculosis, one resistant and one susceptible to antibiotics, using the microplate Alamar blue assay test. The lypophylic fractions of the root and bark showed significant inhibitory activity against both strains, with the hexane fraction of the bark showing the strongest activity (MIC 6.25 microg/ml) against the resistant strain and a significant antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Candida albicans, Aspergillus niger, and Colletotrichum gloeosporioides. The bioassay-guided purification of the bioactive hexane fraction resulted in the isolation and identification of the naphthoquinone plumbagin as one of the metabolites responsible for the biological activity.

Flavonoids from two Lonchocarpus species of the Yucatan Peninsula.

Leaves, stem bark and root of Lonchocarpus xuul and Lonchocarpus yucatanensis were studied separately. A chalcone, 2',4-dimethoxy-6'-hydroxylonchocarpin (), and the flavones 5,4'-dihydroxy-3'-methoxy-(6:7)-2,2-dimethylpyranoflavone (2) and 5,4'-dimethoxy-(6:7)-2,2-dimethylpyrano-flavone (3), together with the known carpachromene (4), were isolated from the leaves of both species. Similarly, the previously reported flavans xuulanin (5) and 3beta-methoxyxuulanin (6), together with the novel 3beta,4beta,5-trimethoxy-4'-hydroxy-(6:7)-2,2-dimethylpyranoflavan (7), 3-hydroxy-4,5-dimethoxy-(6:7)-2,2-dimethyl-pyranoflavan (8), and 3,4-dihydroxy-5-methoxy-(6:7)-2,2-dimethylpyranoflavan (10), were isolated from the stem bark and root of both species. Finally, the known 2',4'-dihydroxy-3'-(3-methylbut-2-enyl) chalcone (13) was obtained from the root of L. xuul only. The structures of the various metabolites were established by interpretation of their spectroscopic data.