Variable-temperature ¹H-NMR studies on two C-glycosylflavones.

Two known C-glycosylflavones, swertisin and embinoidin, were isolated from the leaves of Anthurium aripoense, and characterized by room temperature 1D and 2D NMR experiments. At this temperature, the ¹H- and ¹³C-NMR spectra of these C-glycosylflavones revealed doubling of signals, which suggested the presence of two rotamers in solution. Variable-temperature (VT) ¹H-NMR studies supported this hypothesis.

Toxicity-structure activity evaluation of limonoids from Swietenia species on Artemia salina.

Context: Many plant extracts and compounds are being investigated for their cytotoxicity and hence their medicinal or therapeutic properties. Reports of toxicity studies with limonoid analogs have been sparse and have involved mainly crude extracts. In this study, individual natural limonoids have been isolated and their toxicity manipulated via semisynthesis.

The use of coupled HSQC spectra to aid in stereochemical assignments of molecules with severe proton spectral overlap.

Introduction: A simple glycoside with only 13 carbons exhibited extensive overlapping of four of the glycosidic protons, causing extreme difficulty in the determination of the stereochemistry of the pyranose unit. However, acquisition of a high-resolution coupled heteronuclear single-quantum coherence (HSQC) spectrum overcame this problem. This spectrum provides a useful method for determining vicinal proton coupling constants between strongly coupled protons.

Limonoids from Meliaceae with lipid peroxidation inhibitory activity.

In this study the antioxidant activity of natural limonoids from Meliaceae swietenolide (1), 3,6-O,O-diacetylswietenolide (2), swietenine (3), swietemahonin G (4) and 2-hydroxyswietenine (5) were investigated along with the semi-synthetic analogues (6-25) of compounds 1, 3-4. Lipid peroxidation (LPO) inhibitory assays revealed 85.6, 13.

In vitro antagonistic activity of monoterpenes and their mixtures against 'toe nail fungus' pathogens.

The antibiotic effect of the active ingredients in Meijer medicated chest rub (eucalyptus oil, camphor and menthol) as well as the inactive ingredients (thymol, oil of turpentine, oil of nutmeg and oil of cedar leaf) were studied in vitro using the fungal pathogens responsible for onychomycosis, such as the dermatophytes Tricophyton rubrum, Trichophyton mentagrophytes, Microsporum canis, Epidermophyton fl occosum and Epidermophyton stockdale. The zones of inhibition data revealed that camphor (1). menthol (2).

New erythrolides from the Caribbean gorgonian octocoral Erythropodium caribaeorum.

Seven new briarane diterpenes, erythrolides K-Q (1-7), as well as the known compounds erythrolides A, B, C, F, and J have been isolated from samples of the Caribbean gorgonian Erythropodium caribaeorumcollected at Buccoo Reef and Flying Reef, Tobago. The structures of the new compounds were determined by high-resolution 1H and 13C NMR spectroscopy utilizing COSY, HMBC, HMQC, and NOESY experiments. The structures of erythrolides K and P were confirmed and their relative stereochemistry determined by X-ray crystallographic analysis.