Indole Alkaloids from the Sea Anemone Heteractis aurora and Homarine from Octopus cyanea.

The two new indole alkaloids 2-amino-1,5-dihydro-5-(1H-indol-3-ylmethyl)-4H-imidazol-4-one (1), 2-amino-5-[(6-bromo-1H-indol-3-yl)methyl]-3,5-dihydro-3-methyl-4H-imidazol-4-one (2), and auramine (3) have been isolated from the sea anemone Heteractis aurora. Both indole alkaloids were synthesized for the confirmation of the structures. Homarine (4), along with uracil (5), hypoxanthine (6), and inosine (7) have been obtained from Octopus cyanea.

Detection of a new piperideine alkaloid in the pygidial glands of some Stenus beetles.

Rove beetles of the genus Stenus produce and store bioactive alkaloids like stenusine (3), 3-(2-methylbut-1-enyl)pyridine (4), and cicindeloine (5) in their pygidial glands to protect themselves from predation and microorganismic infestation. The biosynthesis of stenusine (3), 3-(2-methylbut-1-enyl)pyridine (4), and cicindeloine (5) was previously investigated in Stenus bimaculatus, Stenus similis, and Stenus solutus, respectively. The piperideine alkaloid cicindeloine (5) occurs also as a major compound in the pygidial gland secretion of Stenus cicindeloides. The three metabolites follow the same biosynthetic pathway, where the N-heterocyclic ring is derived from L-lysine and the side chain from L-isoleucine. The different alkaloids are finally obtained by few modifications of shared precursor molecules, such as 2,3,4,5-tetrahydro-5-(2-methylbutylidene)pyridine (1). This piperideine alkaloid was synthesized and detected by GC/MS and GC at a chiral phase in the pygidial glands of Stenus similis, Stenus tarsalis, and Stenus cicindeloides.

Elicitors of tansy volatiles from cotton leafworm larval oral secretion.

The feeding of Spodoptera littoralis and Autographa gamma caterpillars on tansy leaves led to a complete different release of volatile monoterpenes, sesquiterpenes, and hexenyl alkanoates. Volatiles were collected from S. littoralis and A. gamma larvae damaged, mechanically wounded, and excised tansy leaves by closed loop stripping analysis. The qualitative and quantitative determination of the volatiles were done by GC-MS- and GC-measurements. The oligosaccharides sucrose, raffinose, stachyose, and verbascose have been detected in oral secretion of the caterpillars of the cotton leafworm S. littoralis. When applied to damaged leaves of tansy plants, these oligosaccharides induce the tansy leaves to emit a similar volatile blend as the feeding of S. littoralis larvae.

Diastereoselective synthesis of a lilac aldehyde isomer and its electrophysiological detection by a moth.

The monoterpene lilac aldehyde (=2-(5-ethenyl-5-methyloxolan-2-yl)propanal) is a widespread flower scent. Lilac aldehyde is emitted in high amounts from nocturnal plant species, and it is highly attractive to nocturnal moth pollinators, such as Hadena bicruris, the pollinating seed predator of Silene latifolia. Lilac aldehyde possesses three stereogenic centers and can occur in eight stereoisomers which induce different antennal responses in H. bicruris. The distribution pattern of stereoisomers differs among plant species, and if H. bicruris has different receptors for detecting different isomers, it may use these differences to discriminate flowers of S. latifolia hosts from flowers of non-host plants. To investigate the question whether the moths have in their antennae one olfactory receptor or several different receptors for the detection of the single lilac aldehyde isomers, (2S,2'S,5'S)-lilac aldehyde was diastereoselectively synthesized. (2S,2'S,5'S)-Lilac aldehyde and its isomeric mixture were tested electrophysiologically on antennae of H. bicruris. The results displayed antennal responses, which are characteristic for a single receptor that detects the different lilac aldehyde isomers.

The floral scent of Taccarum ulei (Araceae): attraction of scarab beetle pollinators to an unusual aliphatic acyloin.

The strongly fragrant thermogenic inflorescences of Taccarum ulei (Araceae) are highly attractive to night-active scarab beetles of Cyclocephala celata and C. cearae (Scarabaeidae, Cyclocephalini), which are effective pollinators of plants in the wild in northeastern Brazil. GC-MS analysis of headspace floral scent samples of T. ulei established that two constituents, (S)-2-hydroxy-5-methyl-3-hexanone (an aliphatic acyloin rarely detected in flowers) and dihydro-ß-ionone (an irregular terpene) accounted for over 96% of the total scent discharge. Behavioral tests (in both field and cages) showed that male and female C. celata and C. cearae were attracted to traps baited with a synthetic mixture of both compounds; however, they were also responsive to (S)-2-hydroxy-5-methyl-3-hexanone alone, which thus functions as a specific attractive cue. These findings support other recent research in suggesting that angiosperms pollinated by cyclocephaline scarab beetles release floral odors of limited complexity in terms of numbers of compounds, but often dominated by unusual compounds that may ensure attraction of specific pollinator species.

Skimming behaviour and spreading potential of Stenus species and Dianous coerulescens (Coleoptera: Staphylinidae).

Rove beetles of the genus Stenus Latreille and the genus Dianous Leach possess pygidial glands containing a multifunctional secretion of piperidine and pyridine-derived alkaloids as well as several terpenes. One important character of this secretion is the spreading potential of its different compounds, stenusine, norstenusine, 3-(2-methyl-1-butenyl)pyridine, cicindeloine, α-pinene, 1,8-cineole and 6-methyl-5-heptene-2-one. The individual secretion composition enables the beetles to skim rapidly and far over the water surface, even when just a small amount of secretion is emitted. Ethological investigations of several Stenus species revealed that the skimming ability, skimming velocity and the skimming behaviour differ between the Stenus species. These differences can be linked to varied habitat claims and secretion saving mechanisms. By means of tensiometer measurements using the pendant drop method, the spreading pressure of all secretion constituents as well as some naturally identical beetle secretions on the water surface could be established. The compound 3-(2-methyl-1-butenyl)pyridine excelled stenusine believed to date to be mainly responsible for skimming relating to its surface activity. The naturally identical secretions are not subject to synergistic effects of the single compounds concerning the spreading potential. Furthermore, evolutionary aspects of the Steninae's pygidial gland secretion are discussed.

Biosynthesis of the defensive alkaloid cicindeloine in Stenus solutus beetles.

To protect themselves from predation and microorganismic infestation, rove beetles of the genus Stenus produce and store bioactive alkaloids like stenusine, 3-(2-methyl-1-butenyl)pyridine, and cicindeloine in their pygidial glands. The biosynthesis of stenusine and 3-(2-methyl-1-butenyl)pyridine was previously investigated in Stenus bimaculatus and Stenus similis, respectively. Both molecules follow the same biosynthetic pathway, where the N-heterocyclic ring is derived from L-lysine and the side chain from L-isoleucine. The different alkaloids are finally obtained by slight modifications of shared precursor molecules. The piperideine alkaloid cicindeloine occurs as a main compound additionally to (E)-3-(2-methyl-1-butenyl)pyridine and traces of stenusine in the pygidial gland secretion of Stenus cicindeloides and Stenus solutus. Feeding of S. solutus beetles with [D,(15)N]-labeled amino acids followed by GC/MS analysis techniques showed that cicindeloine is synthesized via the identical pathway and precursor molecules as the other two defensive alkaloids.

Biosynthesis of the defensive alkaloid (Z)-3-(2-methyl-1-butenyl)pyridine in Stenus similis beetles.

Most rove beetles of the genus Stenus protect themselves against microorganisms and predators such as ants and spiders by producing the alkaloid stenusine (1) in their pygidial glands. The biosynthesis of 1 was previously investigated in S. bimaculatus, where L-lysine forms the piperidine ring, L-isoleucine the side chain, and acetate the N-ethyl group. In addition to 1, S. similis keeps the pyridine alkaloid (Z)-3-(2-methyl-1-butenyl)pyridine (2) in its pygidial glands. Feeding S. similis beetles with [D,15N]-labeled amino acids followed by GC/MS analysis showed that L-Lys yields the pyridine ring and L-Ile the 2-methyl-1-butenyl side chain. Thus the alkaloids 1 and 2 probably share two precursor molecules in their biosynthesis.

Terpenes from the soft corals Litophyton arboreum and Sarcophyton ehrenbergi.

The new cembrane diterpene (3E,11E)-cembra-3,8(19),11,15-tetraene-7alpha-ol (1), nephthenol (2), and all-trans-peridinin (3) have been isolated from the soft coral Litophyton arboreum. The tetraterpene 3, (+)-7,8-epoxy-7,8-dihydrocembrene C (4), emblide (5), sarcophytoxide (6), sarcoglaucol-16-one (7), guajacophine (8), and 1,4-peroxymuurol-5-ene (9) have been obtained from the soft coral Sarcophyton ehrenbergi. The compounds were characterized primarily by NMR spectroscopy. Some of the terpenes were tested for their antiproliferative activity against the cell lines HUVEC and K-562 and for cytotoxicity against the cell line HeLa, and they showed moderate activities.

New pyridine alkaloids from rove beetles of the genus Stenus (Coleoptera: Staphylinidae).

Three new pyridine alkaloids were detected in the pygidial glands of some Stenus species. The chemotaxonomic significance of the occurrence of these alkaloids and stenusine in different Stenus species is discussed. The antimicrobial properties of (Z)- and (E)-3-(2-methyl-1-butenyl)-pyridine and the deterrent activities of stenusine and norstenusine were investigated.

Synthesis and pharmacological activities of some sesquiterpene quinones and hydroquinones.

Synthesis of protected siphonodictyal C was achieved via drim-7-en-11-al. Some sesquiterpene quinones and hydroquinones were tested for their pharmacological activities in assays in search of antiproliferative, cytotoxic, antiphlogistic, antirheumatic and anti-inflammatory drugs. Wiedendiol B is a ten times stronger cyclooxygenase-2 inhibitor than the reference compound indomethacine. Cyclooxygenase-2 inhibitors are drugs with antiphlogistic and antirheumatic activity.

Drug metabolism studies with the incubated hen's egg. Identification of 2,3,5-trihydroxybenzoic acid as a metabolite of gentisic acid.

Previous investigations have shown that an ex vivo model on the basis of the incubated hen's egg represents a potential alternative to animal experimentation for xenobiotic metabolism studies. This model is characterized by administration of the xenobiotic into the yolk sac and identification of metabolites in the allantoic fluid. In the present study, gentisic acid (2,5-dihydroxybenzoic acid, 2,5-DHBA, CAS 490-79-9) was used as a test substance. The oxidative fate of this salicylate metabolite in human and animal species could not be completely elucidated until now. Inoculation of 2,5-DHBA into the incubated hen's egg in concentrations up to 8 mg/egg did not affect embryo viability. For the metabolism studies a dose of 2 mg/egg was chosen and 2,5-DHBA was identified as the main metabolite in both the free and conjugated form (glucuronidel/sulfate). Two minor metabolites were detected in addition. The first of these could be identified as 2,3,5-trihydroxybenzoic acid (2,3,5-THBA) and the second one as 2-hydroxy-5-methoxybenzoic acid (2-H-5-MBA). 2,3,5-THBA has been characterized as a metabolite of 2,5-DHBA in a vertebrate species for the first time. Since 2,3,5-THBA can be methylated to the guaiacol derivative, 2,5-dihydroxy-3-methoxybenzoic acid (2,5-DH-3-MBA) can not to be excluded as a further possible metabolite. The metabolites were identified by comparative TLC with the authentic reference substances as well as additionally by GC and GC-MS analysis of the trimethylsilyl derivatives. The structures of the synthesized reference substances were confirmed by MS, 1H and 13C NMR spectral data.

Furanocembranoids from the soft corals Sinularia asterolobata and Litophyton arboreum.

The new cembranoid diterpene danielid (1) along with 3alpha-ethoxyfuranocembranoid 2, pukalide (3), 13alpha-acetoxypukalide (4), furanocembranoid 5, and furanosesquiterpene 6 have been isolated from the soft coral Sinularia asterolobata. The furanocembranoid diterpene 11beta,12beta-epoxypukalide (7) and the sesquiterpene (-)-bicyclogermacrene (8) have been obtained from the soft coral Litophyton arboreum. The structures were elucidated primarily by NMR spectroscopy. The furanocembranoids 2, 4, and 5 show good antiproliferative activities against the cell lines L-929 and K-562, and weak cytotoxic effects on HeLa cells.

Capnellenes from the soft coral Dendronephthya rubeola.

Four new acetoxycapnellenes 1-4, the first epoxyprecapnellene 5, along with the known dihydroxycapnellene 6 and monoacetoxycapnellene 7, have been isolated from the soft coral Dendronephthya rubeola. The structures were determined primarily by NMR spectroscopy. The compounds 6 and 7 showed a good antiproliferative activity against the cell line L-929 (murine fibroblasts) and a good cytotoxic activity against the HeLa (human cervix carcinoma) cell line. Compound 6 strongly inhibits the interaction of the oncogenic transcription factor Myc with its partner protein Max. Myc/Max-Interaction inhibitors are therapeutically interesting compounds in oncology.

Stenusine, an antimicrobial agent in the rove beetle genus Stenus (Coleoptera, Staphylinidae).

Stenusine is well known as the alkaloid, discharged by the rove beetle, genus Stenus Latreille (Coleoptera, Staphylinidae). The Stenus beetles employ the alkaloid as an escape mechanism when on water surfaces. In the case of danger, they lower their abdomen and emit stenusine from their pygidial glands. Stenusine shows a low surface tension and therefore a high spreading pressure; these properties propel the beetle quickly over the water. Many Steninae do not live in habitats with open waters, but in detritus, leaf litter, mosses, etc. This raises the possibility that stenusine might also have another function, e.g., as antibiotic or fungicide. Stenus beetles show an intense grooming behaviour. With gas chromatography-mass spectrometry analyses we could prove that they cover themselves with their secretion. To tests its antimicrobial properties we conducted agar diffusion tests with stenusine and norstenusine, another substance that is abundant in most Stenus species. Both compounds have an antimicrobial effect on entomopathogenic bacteria and fungi. Stenusine not only allows for an extraordinary method of locomotion on water surfaces, it also protects the Steninae from being infested with microorganisms.

Biosynthesis of stenusine.

The rove beetles of the genus Stenus Latreille synthesize the alkaloid stenusine in their pygidial glands, which are located in the last three segments of their abdomen. It is proposed that stenusine is derived from the two amino acids, L-lysine and L-isoleucine. Feeding S. bimaculatus beetles with deuterium-labeled amino acids and using GC/MS analysis showed that L-lysine forms the piperidine ring of the stenusine molecule. The side chain originates from L-isoleucine and the N-ethyl group from acetate.

Intrageneric differences in the four stereoisomers of stenusine in the rove beetle genus, Stenus (Coleoptera, Staphylinidae).

Most species of the rove beetle genus Stenus employ the spreading alkaloid stenusine as an escape mechanism on water surfaces. In the case of danger, they emit stenusine from their pygidial glands, and it propels them over the water very quickly. Stenusine is a chiral molecule with four stereoisomers: (2'R,3R)-, (2'S,3R)-, (2'S,3S)-, and (2'R,3S)-stenusine. The percentile ratio of these four isomers is only known for the most common species of the genus: Stenus comma. With the intention of determining the stereoisomer ratios of five additional species from the two subgenera, Stenus and Hypostenus, we used GC/mass spectrometry measurements with a chiral phase. The results showed that the ratio differs among the genus. These findings can be a basis for chemotaxonomy. It is also possible that the biological function of stenusine, e.g., as antibiotic or fungicide, varies with changing stereoisomer composition.

Cembranoid diterpenes and a briarane diterpene from corals.

Two new cembrane diterpenes (+)-polydactylide (1) and (+)-7alpha,8beta-dihydroxydeepoxysarcophine (2) together with (+)-sarcophine (3) and (+)-sarcophytoxide (4) have been isolated from the soft coral Sinularia polydactyla. The new cembrane diterpene (-)-7beta-hydroxy-8alpha-methoxydeepoxysarcophine (5) has been obtained from the soft coral Sarcophyton trocheliophorum and the known briarane diterpene briaexcavatolide W (6) from the gorgonian coral Briareum sp.The structures were determined primarily by NMR spectroscopy. The assignment of NMR signals was performed by means of (1)H-(1)H COSY, ROESY, HMQC and HMBC experiments.

Biotechnological production and bioactivities of mollisin and two new, structurally related fungal naphthoquinone metabolites.

The antibiotic and fungicidal deuteromycete Mollisia caesia Sacc. was cultivated on a large scale. Mollisin (1; = 8-(dichloroacetyl)-5-hydroxy-2,7-dimethylnaphthalene-1,4-dione) and two new tri- and tetrahalogenated metabolites, mollisin A (2) and mollisin B (3) were isolated from M. caesia. The formation of 2 and 3 indicates that the biosynthesis of these compounds starts from a C(16) polyketide (Scheme). Mollisin (1) shows strong fungicidal activities against Sclerophoma pityophila (Corda) v. Höhn and Heterobasidion annosum (Fr.) Bref., which is one of the most-destructive basidiomycetes in coniferous forests. The metabolites 1-3 possess interesting pharmacological activities in assays in search of anti-inflammatory and antiproliferative drugs.