GC-MS AND Chemometric Analysis of the Essential Oils Obtained from Mexican Commercial Chamomilla Recutita Teas.

The essential oils prepared by hydrodistillation of twenty-one brands of German chamomile (S1-S21) commercialized in Mexico were analyzed by GS-MS. Altogether, twenty-four different compounds were identified in the analyzed samples, varying from 77 to 100 % of the total composition. Multivariate analyses were applied to explore similarity/dissimilarity and correlation between all samples; the results revealed a strong correlation among samples S4, S5, and S7-S21 due to the presence of (Z)-en-yn-dicycloether [(Z)-tonghaosu], α-bisabolol, ß-farnesene, ß-eudesmol, and xanthoxylin. The samples S1-S3 and S6 were clustered separately. Samples S1, S3, and S6 were characterized by their higher content of bisabolol oxide A (38.78 %, 51.84 %, and 70.46 %, respectively) as most known chemotypes of German chamomile, but only S1 and S3 contained chamazulene. Finally, S2 differed from the others because of its high content of (E)-anethole (62.28 %), suggesting a case of adulteration or substitution of the crude drug employed for manufacturing the product.

Micro-Morphology characterization and HS-SPME-GC-MS Analysis of Floral parts of Quararibea funebris (La Llave) Vischer, traditionally known as Rosita de Cacao.

The flowers of Quararibea funebris are used to make a traditional drink called tejate, to which they add aroma, flavor and consistency. The study aims to profile the morphoanatomy of the floral parts of Q. funebris and analyze the changes in its volatile chemical composition during the drying process from 0 to 180 days by HS-SPME-GC-MS. The calyx, corolla, androecium, and gynoecium have distinct characteristics, such as non-glandular fused stellate trichomes, calcium oxalate crystals, and large secretory ducts. Histochemical localization reveals the presence of mucilage and total lipids in all parts of the flower. The chemical analysis of the essential oil, extracted from the flowers, showed that transfarnesol and geraniol were the most abundant compounds, with a yield of 0.04 %. HS-SPME analysis indicated that fresh flowers had a more complex composition than dried ones. In total, 31 components were identified. Nonanal and geranyl acetone were found to be distinctive components of dried flowers. Microscopic examination helps in identifying and authenticating raw materials and also reveals the presence of secretory ducts in all floral parts, which is a distinctive feature. The chemical profile of volatiles provides an important parameter for the evaluation of the quality of Rosita de Cacao raw materials.

Calmodulin-Targeting Molecules from Ageratina grandifolia.

Four new natural chemical entities, including 2-hydroxy-α-truxillic acid (2), (3R,4S)-2,2-dimethyl-3-hydroxy-4-(1-angeloyloxy)-6-acetyl-7-methoxychromane (3), N-tricosanoyltyramine (4), and grandifolamide (5), were isolated along with 11 known compounds (1, 6-15) from the aerial parts of Ageratina grandifolia. The chemical structures were elucidated using chemical derivatization and HR-MS, NMR, and DFT-calculated chemical shifts, combined with DP4+ statistical analysis. It was found that 2 decomposed into its biogenetic precursor, o-coumaric acid, upon standing at room temperature for a few weeks. 3,5-Diprenyl-4-hydroxyacetophenone (8), O-methylencecalinol (10), encecalin (11), and encecalinol (12) bound to calmodulin (CaM) with higher affinity than chlorpromazine, a well-known CaM inhibitor. Molecular dynamics studies revealed that the complexes of these compounds with CaM remained stable during the simulation. Altogether these results revealed the therapeutic and research tool potential of compounds 8, 10, 11, and 12.

Echeveria Pallida: Inhibiting Adhesion of Fibroblasts From Pterygium and Neutrophil Extracellular Traps Production.

Context: Pterygium, meaty eyes, is a disease that produces a triangular, conjunctival-epithelial, neovascularized overgrowth covering the cornea, which can cause vision loss. Histological characterization of Pterygium reveals the presence of proliferating fibroblasts (FBs) that remodel the extracellular matrix, with infiltration of immune cells, causing chronic inflammation. The fresh juice of Echeveria pallida E. Walther (Crassulaceae), mechanically extracted from the leaves, can be used to lubricate the eyes and remove Pterygium, even in advanced, degenerative ocular disease. Objective: This study aimed to explore the healing mechanisms of an ethanolic extract of E. pallida on pterygium-derived FBs, lymphocytes, and neutrophils. Design: The research team designed an in-vitro study. Primary cultures of FBs were obtained from fresh, surgical pterygium tissues, and neutrophils and mononuclear cells were purified from the peripheral blood of healthy donors. Intervention: An ethanolic extract of E. pallida was evaluated at 30, 50, 80, 100, 200, and 300 µg/mL-the intervention groups-for viability and proliferation of FBs and lymphocytes. The study included a negative control with no extract, and a positive control, Mitomycin C (MMC), used as a FB proliferation inhibitor and anti-inflammatory. Because some reports have suggested that DMSO at low concentrations can stimulate or inhibit lymphocyte proliferation depending on the cell type, the study also included a DMSO control. Outcome Measures: The measures included an analysis of E. pallida's effects on the proliferation and viability of FBs, the proliferation of human lymphocytes, and human neutrophil extracellular traps (NETs) production. NETs were induced using biochemical and microbiological stimuli-phorbol myristate acetate (PMA), hypochlorous acid (HOCl), Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans-through fluorescence microscopy. Results: The ethanolic extract didn't affect the viability or proliferation of pterygium-derived FBs and human blood lymphocytes, but it showed significant inhibitory activity, from 100 µg/mL, on FB adhesion and the production of NETs. Conclusion: The study found scientific evidence that supports the effects of an extract of the medicinal plant E. pallida in inhibiting the adhesion of FBs derived from human pterygium and NET production.

4-Phenylcoumarin (4-PC) Glucoside from Exostema caribaeum as Corrosion Inhibitor in 3% NaCl Saturated with CO2 in AISI 1018 Steel: Experimental and Theoretical Study.

The corrosion inhibition of 5-O-ß-D-glucopyranosyl-7-methoxy-3',4'-dihydroxy-4-phenylcoumarin (4-PC) in AISI 1018 steel immersed in 3% NaCl + CO2 was studied by electrochemical impedance spectroscopy (EIS). The results showed that, at just 10 ppm, 4-PC exerted protection against corrosion with Õ² = 90% and 97% at 100 rpm. At static conditions, the polarization curves indicated that, at 5 ppm, the inhibitor presented anodic behavior, while at 10 and 50 ppm, there was a cathodic-type inhibitor. The inhibitor adsorption was demonstrated to be chemisorption, according to the Langmuir isotherm for 100 and 500 rpm. By means of SEM-EDS, the corrosion inhibition was demonstrated, as well as the fact that the organic compound was effective for up to 72 h of immersion. At static conditions, dispersion-corrected density functional theory results reveal that the chemical bonds established by the phenyl group of 4-PC are responsible of the chemisorption on the steel surface. According with Fukui reactivity indices, the molecules adsorbed on the metal surface provide a protective cover against nucleophilic and electrophilic attacks, pointing to the corrosion inhibition properties of 4-PC.

α-Glucosidase Inhibitors from Ageratina grandifolia.

Fractionation of an aqueous extract from the aerial parts of Ageratina grandifolia yielded a new natural product, namely, 4-hydroxy-3-((S)-1'-angeloyloxy-(R)-2',3'-epoxy-3'-methyl)butylacetophenone (1), along with eight known compounds, including three flavonoids (2-4) and five chromenes (5-9). NMR data interpretation and DFT-calculated chemical shifts combined with DP4+ statistical and J-DP4 probability analyses allowed for the complete characterization of compound 1. The presence of compound 1 in a plant that biosynthesizes 2,2-dimethylchromenes is noteworthy, because an epoxy derivative has long been postulated as the reaction intermediate from the prenylated p-hydroxyacetophenones to cyclic dimethylchromenes. So far, this key intermediate has not been isolated, due to its purported chemical instability. Thus, this is the first report of a potential epoxide intermediate, leading to any of the chromene constituents of this plant. Compounds 1-9 inhibited yeast α-glucosidase with IC50 values ranging from 0.79 to 460 µM (acarbose, IC50 = 278.7 µM). The most active compounds were quercetagetin-7-O-(6-O-caffeoyl-ß-d-glucopyranoside (3) and 6-hydroxykaempferol-7-O-(6-O-caffeoyl-ß-d-glucopyranoside (4). Kinetic analysis of 3 revealed its mixed-type inhibitor nature. Docking studies into the crystallographic structure of yeast α-glucosidase (pdb 3A4A) predicted that 3 and 4 bind at the catalytic site of the enzyme.

Antinociceptive Activity of Compounds from the Aqueous Extract of Melampodium divaricatum.

A decoction prepared from the aerial parts of Melampodium divaricatum showed antinociceptive and antihyperalgesic responses when tested in the formalin model in mice. From the CH2 Cl2 fraction of the decoction, two non-previously reported secondary metabolites, 3-O-ß-D-glucopyranosyl-16α-hydroxy-ent-kaurane (1) and melampodiamide (2) [(2'R*,4'Z)-2'-hydroxy-N-[(2S*,3S*,4R*)-1,3,4-trihydroxyoctadec-2-yl]tetracos-4-enamide] were separated and characterized by spectroscopic, spectrometric, and computational techniques. The flavonoids isoquercitrin and hyperoside, which possessed noted antinociceptive properties, were obtained from the active AcOEt fraction of the decoction. The chemical composition of the essential oil of the plant was also analyzed by gas chromatography-mass spectrometry. The major constituents were (E)-caryophyllene, germacrene D, ß-elemene, δ-elemene, γ-patchoulene, and 7-epi-α-selinene. Headspace solid-phase microextraction analysis detected (E)-caryophyllene as the main volatile compound of the plant.

Flavonoids and Terpenoids with PTP-1B Inhibitory Properties from the Infusion of Salvia amarissima Ortega.

An infusion prepared from the aerial parts of Salvia amarissima Ortega inhibited the enzyme protein tyrosine phosphatase 1B (PTP-1B) (IC50~88 and 33 µg/mL, respectively). Phytochemical analysis of the infusion yielded amarisolide (1), 5,6,4'-trihydroxy-7,3'-dimethoxyflavone (2), 6-hydroxyluteolin (3), rutin (4), rosmarinic acid (5), isoquercitrin (6), pedalitin (7) and a new neo-clerodane type diterpenoid glucoside, named amarisolide G (8a,b). Compound 8a,b is a new natural product, and 2-6 are reported for the first time for the species. All compounds were tested for their inhibitory activity against PTP-1B; their IC50 values ranged from 62.0 to 514.2 µM. The activity was compared to that of ursolic acid (IC50 = 29.14 µM). The most active compound was pedalitin (7). Docking analysis predicted that compound 7 has higher affinity for the allosteric site of the enzyme. Gas chromatography coupled to mass spectrometry analyses of the essential oils prepared from dried and fresh materials revealed that germacrene D (15) and ß-selinene (16), followed by ß-caryophyllene (13) and spathulenol (17) were their major components. An ultra-high performance liquid chromatography coupled to mass spectrometry method was developed and validated to quantify amarisolide (1) in the ethyl acetate soluble fraction of the infusion of S. amarissima.

α-Glucosidase Inhibitors from Malbranchea flavorosea.

From an extract prepared from the grain-based culture of Malbranchea flavorosea two new polyketides, namely, 8-chloroxylarinol A (1) and flavoroseoside (2), along with the known compounds xylarinol A (3), xylarinol B (4), massarigenins B and C (5 and 6), and clavatol (7), were isolated. The structures of 1 and 2 were elucidated using spectroscopic methods and corroborated by single-crystal X-ray diffraction analysis. In the case of compound 2 the absolute configuration at the stereogenic centers was established according to the method of Flack. In addition, the X-ray structure of compound 6 is reported for the first time. Compounds 3, 4, and 6 significantly inhibited yeast α-glucosidase. Compound 6 also inhibited the postprandial peak during an oral sucrose tolerance assay when tested in vivo, using normal and NA/STZ-induced hyperglycemic mice.

Anti-Hyperglycemic Activity of Major Compounds from Calea ternifolia.

Demethylisoencecalin (1) and caleins A (4) and C (5) (3.16-31.6 mg/kg, p.o.), the major components from an infusion of Calea ternifolia controlled postprandial glucose levels during an oral sucrose tolerance test (OSTT, 3 g/kg) in normal and nicotinamide/streptozotocin (NA/STZ, 40/100 mg/kg) hyperglicemic mice. The effects were comparable to those of acarbose (5 mg/kg). During the isolation of 1, 4, and 5, four additional metabolites not previously reported for the plant, were obtained, namely 6-acetyl-5-hydroxy-2-methyl-2-hydroxymethyl-2H-chromene (3), herniarin (6), scoparone (7), and 4',7-dimethylapigenin (8). In addition, the structure of calein C (5) was confirmed by X-ray analysis. Pharmacological evaluation of the essential oil of the species (31.6-316.2 mg/kg, p.o.) provoked also an important decrement of blood glucose levels during an OSTT. Gas chromatography coupled with mass spectrometry (GC-MS) analysis of the headspace solid phase microextraction (HS-SPME)-adsorbed compounds and active essential oil obtained by hydrodistillation revealed that chromene 1 was the major component (19.92%); sesquiterpenes represented the highest percentage of the essential oil content (55.67%) and included curcumene (7.10%), spathulenol (12.95%) and caryophyllene oxide (13.0%). A suitable High Performance Liquid Chromatography (HPLC) method for quantifying chromenes 1 and 6-hydroxyacetyl-5-hydroxy-2,2-dimethyl-2H-chromene (2) was developed and validated according to standard protocols.

α-Glucosidase Inhibitors from Vauquelinia corymbosa.

The α-glucosidase inhibitory activity of an aqueous extract and compounds from the aerial parts of V. corymbosa was demonstrated with yeast and rat small intestinal α-glucosidases. The aqueous extract inhibited yeast α-glucosidase with a half maximal inhibitory concentration (IC50) of 28.6 µg/mL. Bioassay-guided fractionation of the extract led to the isolation of several compounds, including one cyanogenic glycoside [prunasin (1)], five flavonoids [(-)-epi-catechin (2), hyperoside (3), isoquercetin (4), quercitrin (5) and quercetin-3-O-(6''-benzoyl)-ß-galactoside (6)] and two simple aromatic compounds [picein (7) and methylarbutin (8)]. The most active compound was 6 with IC50 values of 30 µM in the case of yeast α-glucosidase, and 437 µM in the case of the mammalian enzyme. According to the kinetic analyses performed with rat and yeast enzymes, this compound behaved as mixed-type inhibitor; the calculated inhibition constants (Ki) were 212 and 50 µM, respectively. Molecular docking analyses with yeast and mammalian α-glucosidases revealed that compound 6 bind differently to these enzymes. Altogether, the results of this work suggest that preparations of V. corymbosa might delay glucose absorption in vivo.

Development of a UHPLC-PDA method for the simultaneous quantification of 4-phenylcoumarins and chlorogenic acid in Exostema caribaeum stem bark.

Potential toxic effects in mice of an infusion prepared from the stem bark of Exostema caribaeum was assessed by means of the Lorke procedure. The preparation was not found to be toxic, with the LD50 value estimated to be more than 5 g/kg. This preparation at 100, 300, and 500 mg/kg also caused a significant hypoglycemic effect and a reduction in the postprandial glycemia peak in both normal and nicotinamide/streptozotocin (NA/STZ)-diabetic mice in an oral sucrose tolerance test. Phytochemical analysis of the infusion revealed that the major active principles are 4-phenylcoumarins (2-8) and chlorogenic acid (1). During this process, a new 4-phenylcoumarin was isolated along with several known analogues. The structure of the new compound was established as 5-O-[ß-D-xylopyranosyl-(1→6)-ß-D-glucopyranosyl]-7,3',4'-trihydroxy-4-phenylcoumarin (2) by spectroscopic means. A simple, efficient, fast, and reliable UHPLC-PDA analytical method for quantifying 4-phenylcoumarins and chlorogenic acid (1) was developed and validated. Parameters assessed for the method validation were selectivity, linearity, the limits of detection (LOD) and quantification (LOQ), precision, and accuracy. It was found that all calibration curves showed good linearity (R(2) > 0.9931), within the range of concentrations tested.

The Genus Ageratina (Asteraceae) in America: An Insight into its Chemistry and Pharmacological Potential.

BACKGROUND: Ageratina is an American genus of the tribe Eupatorieae (Asteraceae), comprising about 320 species. In Mexico, some species of this genus are highly valued for their medicinal properties, particularly A. pichinchensis, A. petiolaris, and A. grandifolia. Furthermore, herbal preparations of A. pichinchensis are available for treating several mycoses. AIMS AND OBJECTIVE: The present review is aimed to summarize the chemical and pharmacological properties of 37 species of the Ageratina genus up to April, 2022. METHODS: Data were recorded using online scientific databases, including Scopus, PubMed, Google Scholar, Taylor and Francis Imprints, National Center for Biotechnology Information, Science Direct, JSTOR, and SciFinder. The information was gathered from research articles, relevant books on herbal medicinal plants and the history of medicinal plants from Mexico, theses, reports, and web pages. RESULTS: The specialized metabolites present in the Ageratina genus belong to different chemical classes, including flavonoids, benzyl benzoates, benzofurans, chromenes, and terpenoids. The chromenes, benzofurans, and benzyl benzoates are the metabolites most widespread in the genus. So far, the species more thoroughly investigated is A. adenophora. Ageratina has received little attention from the pharmacological point of view. The studies are limited to 10 species. Biological studies have been conducted on extracts and/or compounds isolated from plants collected mainly from China and Mexico. The results revealed that the extracts and metabolites possess several biological activities, including antiviral, antioxidant, antimicrobial, anti-inflammatory, antinociceptive, antifeedant, larvicidal, acaricidal, antidiabetic, antiprotozoal, and wound-healing properties. In the case of A. pichinchensis, A. petiolaris, and A. grandifolia, the pharmacological studies provided evidence for their use for treating gastrointestinal complaints and diabetes. Furthermore, herbal preparations of A. pichinchensis are now widely used for alleviating onychomycosis. A. adenophora, is the most investigated species, chemically and biologically; however, some hepatotoxicity effect has been recorded. CONCLUSION: This review recapitulates information on the Ageratina genus, highlighting the phytochemistry and biological activities of the species investigated. It is important to point out that the pharmacological potential of this large genus remains largely unexplored.

Discovery of inhibitors of protein tyrosine phosphatase 1B contained in a natural products library from Mexican medicinal plants and fungi using a combination of enzymatic and in silico methods*.

This work aimed to discover protein tyrosine phosphatase 1B (PTP1B) inhibitors from a small molecule library of natural products (NPs) derived from selected Mexican medicinal plants and fungi to find new hits for developing antidiabetic drugs. The products showing similar IC50 values to ursolic acid (UA) (positive control, IC50 = 26.5) were considered hits. These compounds were canophyllol (1), 5-O-(ß-D-glucopyranosyl)-7-methoxy-3',4'-dihydroxy-4-phenylcoumarin (2), 3,4-dimethoxy-2,5-phenanthrenediol (3), masticadienonic acid (4), 4',5,6-trihydroxy-3',7-dimethoxyflavone (5), E/Z vermelhotin (6), tajixanthone hydrate (7), quercetin-3-O-(6″-benzoyl)-ß-D-galactoside (8), lichexanthone (9), melianodiol (10), and confusarin (11). According to the double-reciprocal plots, 1 was a non-competitive inhibitor, 3 a mixed-type, and 6 competitive. The chemical space analysis of the hits (IC50 < 100 µM) and compounds possessing activity (IC50 in the range of 100-1,000 µM) with the BIOFACQUIM library indicated that the active molecules are chemically diverse, covering most of the known Mexican NPs' chemical space. Finally, a structure-activity similarity (SAS) map was built using the Tanimoto similarity index and PTP1B absolute inhibitory activity, which allows the identification of seven scaffold hops, namely, compounds 3, 5, 6, 7, 8, 9, and 11. Canophyllol (1), on the other hand, is a true analog of UA since it is an SAR continuous zone of the SAS map.

Protein tyrosine phosphatase 1B inhibitory activity of compounds from Justicia spicigera (Acanthaceae).

An infusion from the aerial parts of Justicia spicigera Schltdl., an herb commonly used to treat diabetes, inhibited the activity of protein tyrosine phosphatase 1B (PTP1B). Two undescribed compounds, 2-N-(p-coumaroyl)-3H-phenoxazin-3-one, and 3″-O-acetyl-kaempferitrin, along with kaempferitrin, kaempferol 7-O-α-L-rhamnopyranoside, perisbivalvine B and 2,5-dimethoxy-p-benzoquinone were isolated from the active extract. Their structures were elucidated by a combination of spectroscopic and spectrometric methods. The isolates were evaluated for their inhibitory activity against PTP1B; the most active compounds were 2-N-(p-coumaroyl)-3H-phenoxazin-3-one, and perisbivalvine B with IC50 values of 159.1 ± 0.02 µM and 106.6 ± 0.01 µM, respectively. However, perisbivalvine B was unstable. Kinetic analysis of 2-N-(p-coumaroyl)-3H-phenoxazin-3-one and 2,5-dimethoxy-p-benzoquinone (obtained in good amounts) indicated that both compounds behaved as parabolic competitive inhibitors and bind to the enzyme forming complexes with 1:1 and 1:2 stoichiometry. Docking of 2-N-(p-coumaroyl)-3H-phenoxazin-3-one and 2,5-dimethoxy-p-benzoquinone to PTP1B1-400 predicted a good affinity of these compounds for PTP1B catalytic site and demonstrated that the binding of a second ligand is sterically possible. The 1:2 complex was also supported by the second docking analysis, which predicted an important contribution of π-stacking interactions to the stability of these 1:2 complexes. Finally, an UHPLC-MS method was developed and validated to quantify the content of kaempferitrin in the infusion of the plant.

Antinociceptive Effect of an Aqueous Extract and Essential Oil from Baccharis heterophylla.

Infusions and poultices prepared from the aerial parts of Baccharis heterophylla Kunth (Asteraceae) are widely used in Oaxaca (Mexico) for relieving painful and inflammatory complaints. Therefore, the antinociceptive potential of an aqueous extract (31.6-316 mg/kg, p.o.) and essential oil (30-177 µg/paw, i.pl.) of the plant was assessed using the formalin test. Both preparations inhibited the formalin-induced nociception response (100-316 mg/kg and 100-177 µg/paw, respectively) during the test's second phase. Chemical analysis of the aqueous extract revealed that the major active components were chlorogenic acid (1), 3,4-di-O-(E)-caffeoylquinic acid (2), 3,5-di-O-(E)-caffeoylquinic acid (3), 4,5-di-O-(E)-caffeoylquinic acid (4), 3,5-di-O-(E)-caffeoylquinic acid methyl ester (5), apigenin (6), genkwanin (7), acacetin (8). Compounds 1-5 and 8 are new for B. heterophylla. A high-pressure liquid chromatographic method for quantifying chlorogenic acid (1) and di-caffeoylquinic acids 2-4 in the plant was developed and validated. Analyses of the essential oil and the headspace solid-phase microextraction products, via gas-chromatography-mass spectrometry, revealed that the major volatiles were ß-pinene, myrcene, D-limonene, ß-caryophyllene, and α-caryophyllene, which have demonstrated antinociceptive properties.

Hypoglycemic activity of extracts and compounds from the leaves of Hintonia standleyana and H. latiflora: potential alternatives to the use of the stem bark of these species.

The CH(2)Cl(2)-MeOH (1:1) extract of the leaves of Hintonia standleyana and H. latiflora caused significant decrease in blood glucose levels in both normal and streptozotozin (STZ)-induced diabetic rats when compared with vehicle-treated groups (p < 0.05). These extracts were not toxic to mice according to the Lorke criteria. From the hypoglycemic extract of H. standleyana, two new 4-phenylcoumarins, namely, 6''-O-acetyl-5-O-beta-d-galactopyranosyl-7,4'-dihydroxy-4-phenylcoumarin (1) and 6''-O-acetyl-5-O-beta-d-galactopyranosyl-7,3',4'-trihydroxy-4-phenylcoumarin (2), were obtained. The analogous extract of H. latiflora yielded the new 5-O-[beta-d-xylopyranosyl-(1-->6)-beta-d-glucopyranosyl]-7,4'-dimethoxy-4-phenylcoumarin (3) along with several known compounds, including ursolic acid and desoxycordifolinic acid. Phenylcoumarins 1 and 2 showed hypoglycemic activity. HPLC profiles of the leaf extracts of both plants revealed the presence of known hypoglycemic phenylcoumarins as well as chlorogenic acid. The overall results have indicated that the leaves of H. standleyana and H. latiflora possess similar antidiabetic potential to their stem bark. Therefore, the leaves from these species could represent an alternative to the use of their stem bark, which, in turn, would contribute to the conservation of these Mexican medicinal plants.

Phytotoxic activity and conformational analysis of thymol analogs from Hofmeisteria schaffneri.

Bioassay-guided fractionation of two phytotoxic extracts (a CH(2)Cl(2)-MeOH (1:1) and an aqueous) prepared from the aerial parts of Hofmeisteria schaffneri led to isolation of thymol analogs 3-5, along with seven known compounds, 1, 2 and 6-10. Compounds 3-5 were identified by spectroscopic methods as 1,4-bis(2'-hydroxy-4'-methylphenyl)butane-1,4-dione (3), 2-isopropyl-5-methylphenyl (2Z)-2-methylbut-2-enoate (4) and 2-hydroxy-2-(2-hydroxy-4-methylphenyl)propane-1,3-diyl (2Z,2'Z)bis(2-methylbut-2-enoate) (5) and designated trivial names of hofmeisterins II-IV, respectively. Their conformational behavior was also studied by molecular modeling using density functional theory calculations at the B3LYP/DGDZVP level. Compounds 1-4 and 6-10 significantly inhibited radicle growth of seedlings of Amaranthus hypochondriacus and Echinochloa crus-galli in the Petri dish bioassay with IC(50)'s10(-4)M. Furthermore, the northymol analog 3 provoked significant bleaching of seedlings of A. hypochondriacus. However, none of the isolates affected either seedling growth or germination of Medicago sativa.

Natural products with calmodulin inhibitor properties.

This review summarizes properties of various naturally occurring compounds with reported calmodulin (CaM)-inhibitory properties which include about 159 natural products belonging to different structural classes. Most inhibitors are alkaloid and peptide type of compounds and have been isolated from a wide variety of natural sources, including many plant species. Among the most potent natural anti-CaM substances, however, are several animal venoms and the antibiotic polymixin. The largest number of compounds described were discovered by means of enzymatic functional assays.