Iridoid glucosides from Wendlandia ligustroides (Boiss. &Hohen.) Blakelock.

Eight iridoid glucosides were reported from the aerial parts of Wendlandia ligustroides. 10-deoxygeniposidic acid (1), 7-deoxygardoside (2), geniposidic acid (3), 7-deoxy-8-epi-loganic acid (4), deacetyl-daphylloside (5), scandoside methyl ester (6), 6-O-methyl-deacetyl-daphylloside (7), 6-O-methyl-scandoside methyl ester (8). Compounds 3 - 8 were isolated as a pure form while 1 and 2 as a mixture. The structures of the compounds 1 - 8 were established by spectroscopic methods including 1D-NMR (1H NMR, 13C NMR, DEPT-135), 2D-NMR (COSY, NOESY, HSQC, HMBC) and HRMS.

Iridoid glucosides in the endemic Picconia azorica (Oleaceae).

In our continued investigation of plants from the family Oleaceae we have now investigated Picconia azorica endemic to the Azores. Like most species within the family it contains the oleoside-based secoiridoid glucosides ligstroside and oleuropein as the main compounds and in addition verbascoside and echinacoside. As with the previously investigated Picconia excelsa, it also contained the carbocyclic iridoid glucosides involved in the biosynthetic pathway to the oleoside derivatives. However, while P. excelsa contained loganin esterified with some monoterpenoid acids, P. azorica contains similar esters of 7-epi-loganic acid named Picconioside A and B. In addition were found the two 7-O-E/Z-cinnamoyl esters of 7-epi-loganic acid named Picconioside C and D.

Further iridoid glucosides in the genus Manulea (Scrophulariaceae).

From Manulea altissima (Scrophulariaceae) were isolated five known secoiridoid glucosides sweroside, eustomoside, eustoside, secoxyloganin and secologanoside as well as the 4″-O-rhamnopyranosyl-feruloyl ester of adoxosidic acid, named altissimoside. Also, the caffeoyl phenylethanoid glycoside verbascoside was isolated. In addition two previously unknown terpenoid esters of 6ß-hydroxy 8-epi-boschnaloside, named manucoside A and B were isolated from a formerly obtained fraction from the work-up of Manulea corymbosa. The distribution of iridoid glucosides in the Scrophulariaceae is discussed.

Unexpected secoiridoid glucosides from Manulea corymbosa.

From an extract of Manulea corymbosa were isolated four known secoiridoid glucosides (1-4), 10 new monoterpenoid esters of secologanol, namely, manuleosides A-I (5-11, 13, and 14) and dimethyl rhodanthoside A (12), and four new phenylpropanoid esters of carbocyclic iridoid glucosides, manucorymbosides I-IV (15-18). Also, the caffeoyl phenylethanoid glycoside verbascoside was isolated. The presence of secoiridoids apparently derived from loganic acid in the family Scrophulariaceae is unprecedented and greatly unexpected.

Iridoid and phenylethanoid glycosides in the New Zealand sun hebes (Veronica; Plantaginaceae).

The sun hebes are a small clade of New Zealand Veronica formerly classified as Heliohebe. The water-soluble compounds of Veronica pentasepala, Veronica raoulii and Veronica hulkeana were studied and 30 compounds including 15 iridoid glucosides, 12 phenylethanoid glycosides, the acetophenone glucoside pungenin, the mannitol ester hebitol II and mannitol were isolated. Of these, five were previously unknown in the literature: dihydroverminoside and 3,3',4,4'-tetrahydroxy-α-truxillic acid 6-O-catalpyl diester, named heliosepaloside, as well as three phenylethanoid glycoside esters heliosides D, E and F, all derivatives of aragoside. The esters of cinnamic acid derivatives with iridoid and phenylethanoid glycosides and an unusually high concentration of verminoside were found to be the most distinctive chemotaxonomic characters of the sun hebes. The chemical profiles of the species were compared and used to assess the phylogenetic relationships in the group.

Iridoid and phenylethanoid glucosides from Veronica lavaudiana.

From an extract of Veronica (sect. Hebe) lavaudiana we have identified mannitol and isolated 11 iridoid glucosides, the carbohydrate ester hebitol II, and four phenylethanoid glycoside esters. Five of the iridoid glycosides are new; of these, lavaudiosides A, B, and C (2a, 3a, and 4) are 1-mannityl esters of 8-epiloganic acid, while 7e and 7f are 6'-O-caffeoyl derivatives of catalpol. The new phenylethanoid glycoside esters, heliosides A, B, and C (8b-d), are 6'-xylosyl derivatives of aragoside. The structures of the new compounds were elucidated mainly by spectroscopic analysis, but also by chemical degradation. We also demonstrated that the structures of the known glycosides globularitol and hebitols I and II should be revised. These compounds are derivatives of mannitol and not glucitol as previously believed.

Chlorinated iridoid glucosides from Veronica longifolia and their antioxidant activity.

From Veronica longifolia were isolated three chlorinated iridoid glucosides, namely, asystasioside E (6) and its 6-O-esters 6a and 6b, named longifoliosides A and B, respectively. The structures of 6a and 6b were proved by analysis of their spectroscopic data and by conversion to the catalpol ester verproside (5a) or to catalpol (5), respectively. The configuration of the previously known vanilloyl analogue, urphoside B, was shown to be the 6ß-epimer (6c) of the structure originally reported. Longifoliosides A (6a) and B (6b) were found to exhibit radical-scavenging activity against nitric oxide, superoxide, and 2,2-diphenyl-1-picrylhydrazyl radicals.

Sequestration of glucosinolates and iridoid glucosides in sawfly species of the genus Athalia and their role in defense against ants.

In this study, the larval sequestration abilities and defense effectiveness of four sawfly species of the genus Athalia (Hymenoptera: Tenthredinidae) that feed as larvae either on members of the Brassicaceae or Plantaginaceae were investigated. Brassicaceae are characterized by glucosinolates (GLSs), whereas Plantaginaceae contain iridoid glucosides (IGs) as characteristic secondary compounds. Athalia rosae and A. liberta feed on members of the Brassicaceae. Larvae of A. rosae sequester aromatic and aliphatic GLSs of Sinapis alba in their hemolymph, as shown previously, but no indolic GLSs; A. liberta larvae with a narrower host range sequester aliphatic as well as indolic GLSs from their host plant Alliaria petiolata. Larvae of A. circularis and A. cordata are specialized on members of the Plantaginaceae. Athalia circularis utilizes mainly Veronica beccabunga as host plant, whereas A. cordata feeds additionally on Plantago lanceolata. Both sawfly species sequester the IGs aucubin and catalpol. In V. beccabunga, catalpol esters and carboxylated IGs also occur. The high catalpol concentrations in hemolymph of A. circularis can only be explained by a metabolization of catalpol esters and subsequent uptake of the resulting catalpol. The carboxylated IGs of the plant are excreted. The IG-sequestering sawfly species are able to accumulate much higher glucoside concentrations in their hemolymph than the GLS-sequestering species, and the concentration of IGs in hemolymph increases constantly during larval development. The defensive effectiveness of hemolymph that contains GLSs or IGs and of the respective glucosides was tested in feeding-bioassays against a potential predator, the ant Myrmica rubra (Hymenoptera: Formicidae). Hemolymph of IG-sequestering cryptic A. cordata larvae has a higher deterrence potential than hemolymph of the GLS-sequestering conspicuous A. rosae larvae. The results show that glucoside sequestration is widespread in the genus Athalia, but that the specific glucoside uptake can result in different defense effectiveness against a predator species.

Structural revision of some recently published iridoid glucosides.

The structures of six different iridoid glucosides have been revised. Three compounds isolated from Eremostachys glabra and designated 6,9-epi-8-O-acetylshanziside (1), 5,9-epi-penstemoside (2), and 5,9-epi-7,8-didehydropenstemoside (3) have been shown to be identical to the known iridoids barlerin (4, 8-O-acetylshanziside), penstemoside (5), and 7,8-didehydropenstemoside (6), respectively. Another compound named harpagoside-B, isolated from Scrophularia deserti and proposed to be 9-epi-6-O-methylharpagoside (11), was demonstrated from the spectroscopic data given to be the known harpagoside (10b). Finally, two alleged iridoid galactosides from Buddleja crispa named buddlejosides A and B (12a and 12b) have been shown to be the corresponding glucosides; the former is identical to agnuside (13a), while the latter is 3,4-dihydroxybenzoylaucubin (13b), an iridoid glucoside not previously published. This clearly showed that care should be taken with the interpretation of NOEs involving bridgehead protons in iridoid structures because they can be capricious and lead to erroneous structural assignments.

Characterization of polychlorinated alkane mixtures--a Monte Carlo modeling approach.

A Monte Carlo model was developed to characterize the molecular composition of polychlorinated alkane mixtures. The model is based upon a simulation of the free-radical chlorination process by which polychlorinated alkane mixtures are produced industrially from n-alkanes. In the model, the free-radical chlorination reaction was simulated by randomly selecting a position on a partially converted alkane molecule for target by chlorine free-radical attack. The relative reactivities of the hydrogen atoms on the alkane chain towards chlorine free-radical substitution were either determined experimentally or extrapolated from experimental results and incorporated into the model. The result of the simulation is the prediction of the detailed molecular composition of any PCA mixture. Good agreement was found when comparing the distribution of molecules predicted by the model to analytically determined distributions of real PCA mixtures. Results from the model were then coupled with rules describing the action of biological enzymes to estimate the upper limit possible for the aerobic biodegradation of PCA mixtures.

Biodegradation of chlorinated alkanes and their commercial mixtures by Pseudomonas sp. strain 273.

The biodegradation of chlorinated alkanes was studied under oxic conditions with the objective of identifying favorable and unfavorable intramolecular chlorination sequences with respect to the enzymes studied. Several dehalogenating bacterial strains were screened for their ability to degrade middle-chain polychlorinated alkanes as well as a commercial mixture. Of the organisms tested, the most promising was Pseudomonas sp. strain 273, which possesses an oxygenolytic dehalogenase. The effects of carbon chain length (C(6)-C(16)), halogen position, and overall chlorine content (14-61% w/w) were examined using both commercially available compounds and molecules synthesized in our laboratory. The effects of co-substrates, solvents, and inducing agents were also studied. The results with pure chlorinated alkanes showed that the relative positions of the chlorine atoms strongly influenced the total amount of dehalogenation achieved. The greatest dehalogenation yields were associated with terminally chlorinated alkanes. The alpha- and alpha,omega-chlorinated compounds yielded similar results. Vicinal chlorination had the most dramatic impact on degradation. When present on both ends or at the center of the molecule, no dehalogenation was detected. Although partial dehalogenation of 1,2-dichlorodecane was observed, it was likely due to a combination of beta-oxidation and an abiotic mechanism. Cereclor S52 was appreciably dehalogenated in shake flasks only when 1,10-dichlorodecane was present as a co-substrate and after increasing the oil surface area through mechanical emulsification, demonstrating the importance of abiotic factors in degrading commercial polychlorinated alkane mixtures.