Antispasmodic activity of xanthoxyline derivatives: structure-activity relationships

A Medicinal Halophyte Ipomoea pes-caprae (Linn.) R. Br.: A Review of Its Botany, Traditional Uses, Phytochemistry, and Bioactivity

Ipomoea pes-caprae (Linn.) R. Br. (Convolvulaceae) is a halophytic plant that favorably grows in tropical and subtropical countries in Asia, America, Africa, and Australia. Even though this plant is considered a pan-tropical plant, I. pes-caprae has been found to occur in inland habitats and coasts of wider areas, such as Spain, Anguilla, South Africa, and Marshall Island, either through a purposeful introduction, accidentally by dispersal, or by spreading due to climate change. The plant parts are used in traditional medicine for treating a wide range of diseases, such as inflammation, gastrointestinal disorders, pain, and hypertension. Previous phytochemical analyses of the plant have revealed pharmacologically active components, such as alkaloids, glycosides, steroids, terpenoids, and flavonoids. These phytoconstituents are responsible for the wide range of biological activities possessed by I. pes-caprae plant parts and extracts. This review arranges the previous reports on the botany, distribution, traditional uses, chemical constituents, and biological activities of I. pes-caprae to facilitate further studies that would lead to the discovery of novel bioactive natural products from this halophyte.

When a Tritrophic Interaction Goes Wrong to the Third Level: Xanthoxylin From Trees Causes the Honeybee Larval Mortality in Colonies Affected by the River Disease

The "River Disease" (RD), a disorder impacting honeybee colonies located close to waterways with abundant riparian vegetation (including Sebastiania schottiana, Euphorbiaceae), kills newly hatched larvae. Forager bees from RD-affected colonies collect honeydew excretions from Epormenis cestri (Hemiptera: Flatidae), a planthopper feeding on trees of S. schottiana. First-instar honeybee larvae fed with this honeydew died. Thus, we postulated that the nectars of RD-affected colonies had a natural toxin coming from either E. cestri or S. schottiana. An untargeted metabolomics characterization of fresh nectars extracts from colonies with and without RD allowed to pinpoint xanthoxylin as one of the chemicals present in higher amounts in nectar from RD-affected colonies than in nectars from healthy colonies. Besides, xanthoxylin was also found in the aerial parts of S. schottiana and the honeydew excreted by E. cestri feeding on this tree. A larva feeding assay where xanthoxylin-enriched diets were offered to 1^st instar larvae showed that larvae died in the same proportion as larvae did when offered enriched diets with nectars from RD-colonies. These findings demonstrate that a xenobiotic can mimic the RD syndrome in honeybee larvae and provide evidence of an interspecific flow of xanthoxylin among three trophic levels. Further, our results give information that can be considered when implementing measures to control this honeybee disease.

Epormenis cestri secretions in Sebastiania schottiana trees cause mass death of honey bee Apis mellifera larvae in Uruguay

For more than 60 years, sporadic cases of massive summer honey bee larvae mortality in colonies located near freshwater systems with abundant riparian vegetation have been reported in Uruguay. This odd phenomenon, known as “River disease” by beekeepers, can lead to colony death by depopulation. The aim of this study was to detect the causes of larvae death. Different experiments and analyses were performed using affected apiaries located between two important water courses. 1 day old larvae were the most susceptible and substances that killed the larvae were present in the nectar but not in the pollen. A palynological analysis of nectar samples showed that bees collect this resource from commonly pollinated floral species in the country. However, abundant fungi spores and conidia were found, which indicates that the bees also collected honeydews. In the riparian vegetation, bees were observed collecting the secretions of the planthopper Epormenis cestri on Sebastiania schottiana trees. It was found that the mortality period of larvae overlaps with the presence of E. cestri. Larvae maintained in the laboratory were fed (i) nectar from healthy colonies, (ii) nectar from affected colonies, and (iii) secretions of E. cestri. The mortality of the larvae that received nectar from colonies affected with River disease and secretions of E. cestri was higher than the mortality of those receiving nectar from healthy colonies. This represents the first report of planthopper honeydew causing mass larval mortality in honey bees.

Molecular Structure and QSAR Study on Antispasmodic Activity of some Xanthoxyline Derivatives

Semi-empirical molecular orbital calculations at AM1 level were done with the aim to investigate the structure-activity relationships of antispasmodic activities of ten 2-(X-benzyloxy)-4,6-dimethoxyacetophenones with X = H, 4'-F, 4'-NO2, 4'-CH3, 4'-Cl, 3',4'-(CH3)2, 4'-OCH3, 4'-Br, 4'-OCH2C6H5, and 4'-C(CH3)3, against acetylcholine-induced contraction of the guinea pig ileum. The most significant quantum chemical descriptors for this series of compounds were the net atomic charges, nucleophilic and electrophilic frontier electron density, HOMO and LUMO orbitals, and reactivity indices. While no significant correlations were found employing molecular parameters such as heat of formation, dipole moment, molecular polarizability, and so on, good correlations were obtained using the reactivity indices of HOMO and LUMO orbitals at specific atoms of the molecules. These results indicate that the spatial distribution of HOMO and LUMO orbitals over these specific atoms play an important role for an increase of biological activity.

Correlation of activity of 2-(X-benzyloxy)-4,6-dimethoxyacetophenones with topological indices and with the Hansch equation

The antispasmodic activities of the 2-(X-benzyloxy)-4,6-dimethoxyacetophenones (X = H, 4'-F, 4'-NO2, 4'-CH3, 4'-Cl, 3',4'-(CH3)2, 4'-OCH3, 4'-Br, 4'-C(CH3)3, 4'-OCH2C6H5) against acetylcholine-induced contraction of the guinea pig ileum were correlated with different topological indices. Good correlations were obtained through a simple regression equation with electrotopological state indices (Si) for the carbon atoms S(C1) and S(C6). Using multiple linear regression with two variables the best correlations were obtained with carbons in the 6- and 1-positions with sigma. Such results indicate that the corresponding carbon atoms play an important role in the biological activity. The equation of Hansch showed that the activity of these compounds increases when the ring substituent in the benzyloxy group are more highly electron-releasing and hydrophobic.