Chemical defense of an Asian snake reflects local availability of toxic prey and hatchling diet.

Species that sequester toxins from prey for their own defense against predators may exhibit population-level variation in their chemical arsenal that reflects the availability of chemically defended prey in their habitat. Rhabdophis tigrinus is an Asian snake that possesses defensive glands in the skin of its neck ('nuchal glands'), which typically contain toxic bufadienolide steroids that the snakes sequester from consumed toads. In this study, we compared the chemistry of the nuchal gland fluid of R. tigrinus from toad-rich and toad-free islands in Japan and determined the effect of diet on the nuchal gland constituents. Our findings demonstrate that captive-hatched juveniles from toad-rich Ishima Island that had not been fed toads possess defensive bufadienolides in their nuchal glands, presumably due to maternal provisioning of these sequestered compounds. Wild-caught juveniles from Ishima possess large quantities of bufadienolides, which could result from a combination of maternal provisioning and sequestration of these defensive compounds from consumed toads. Interestingly, juvenile females from Ishima possess larger quantities of bufadienolides than do juvenile males, whereas a small sample of field-collected snakes suggests that adult males contain larger quantities of bufadienolides than do adult females. Captive-born hatchlings from Kinkasan Island lack bufadienolides in their nuchal glands, reflecting the absence of toads on that island, but they can sequester bufadienolides by feeding on toads (Bufo japonicus) in captivity. The presence of large quantities of bufadienolides in the nuchal glands of R. tigrinus from Ishima may reduce the risk of predation by providing an effective chemical defense, whereas snakes on Kinkasan may experience increased predation due to the lack of defensive compounds in their nuchal glands.

Red cochineal dye (carminic Acid): its role in nature.

Carminic acid, the well-known red dyestuff from cochineal insects (Dactylopius spp.), is a potent feeding deterrent to ants. This deterrency may be indicative of the natural function of the compound, which may have evolved in cochineals as a chemical weapon against predation. The behavior of an unusual predator is described-the carnivorous caterpillar of a pyralid moth (Laetilia coccidivora)-which is undeterred by carminic acid and feeds on cochineals. The animal has the remarkable habit of utilizing the ingested carminic acid for defensive purposes of its own.

1,2-Dialkyl-4(3H)-quinazolinones in the defensive secretion of a millipede (Glomeris marginata).

Two crystalline components isolated from the defensive secretion of the glomerid millipede, Glomeris marginata, are identified as 1- methyl- 2- ethyl- 4( 3H)- quinazolinone and 1,2- dimethyl- 4( 3H)- quinazolinone. These heterocyclic compounds bear a close structural resemblance to arborine, the chief alkaloid of the Indian medicinal plant, Glycomis arborea Correa.

Sex pheromone of the queen butterfly: chemistry.

Two major components in the "hairpencil" secretion of the male of the queen butterfly (Danaus gilippus berenice) have been identified. One, a crystalline ketone (2,3-dihydro-7-methyl-1H-pyrrolizin-1-one), is known from another danaid butterfly. The other, a viscous terpenoid alcohol (trans, trans-3,7-dimethyldeca-2,6-dien-1,10-diol), is new; its structure is confirmed by an unambiguous synthesis.

Chemical ecology: studies from East Africa.

The International Centre of Insect Physiology and Ecology (ICIPE), in Nairobi, provides a laboratory at which a multinational group of scientists pursues interdisciplinary research. In collaboration with their colleagues in biology, ICIPE chemists have characterized the sex pheromones of the tick which serves as a vector of East Coast fever and have identified a termite queen-cell-building pheromone. The structure of many anthropod defensive chemicals have been determined; most interesting of these are the trinervitenes, structurally novel diterpenoids from nasute termites. Several highly active insect antifeedants were discovered using a simple bioassay to screen selected East African plants. These antifeedants may provide leads for the development of new insect-control techniques.

Dihydromatricaria acid: acetylenic acid secreted by soldier beetle.

The aposematic cantharid beetle Chauliognathus lecontei produces a defensive secretion, from glands in its thorax and abdomen, containing 8-cis-dihydromatricaria acid. Similar acetylenic compounds are known only from certain fungi and flowering plants.

2,5-Dichlorophenol (from ingested herbicide?) in defensive secretion of grasshopper.

The defensive froth emitted by the grasshopper Romalea microptera contains several odorous compounds (phenols, terpenes, benzoquinone), including a chlorinated aromatic compound, 2,5-dichlorophenol. This compound, which is repellent to ants and therefore defensively useful to the grasshopper, probably stems from herbicide or herbicide derivative ingested by the insect with its diet. Although there is precedent for the defensive employ by one species of chemical agents produced by another, no instance was known involving secondary utilization of a pesticide dispensed by man.

Flavonols: pigments responsible for ultraviolet absorption in nectar guide of flower.

The petals of the black-eyed susan (Compositae: Rudbeckia hirta) contain three flavonol glucosides (6,7-dimethoxy-3',4',5-trihydroxyflavone-3-O-glucoside, patulitrin, and quercetagetin). These compounds, which show intense spectral absorption at 340 to 380 nanometers, are restricted in distribution to the petal bases, which are ultraviolet absorbing as a result. Such ultraviolet-absorbing petal zones, known as "nectar guides," are invisible to us, but are visible and of orientation value to the pollinating insect that lands on the flower in search for food. This is the first time that ultraviolet absorption in a nectar guide has been interpreted in chemical terms. In view of the widespread occurrence of flavonols in flowers, it is suggested that these pigments serve specifically for demarcation of ultraviolet petal patterns visible and relevant to insects.

Defense of phalangid: liquid repellent administered by leg dabbing.

The phalangid Vonones sayi has a pair of exocrine defensive glands that secrete quinones (2,3-dimethyl-1,4-benzoquinone and 2,3,5-trimethyl-1,4- benzoquinone). When distributed, the animal emits the secretion, dilutes it with aqueous regurgitated fluid, and effects dosaged delivery of the mixture by brushing it on the assailant with the tips of its forelegs. Predators such as ants are effectively repelled.

Cyclopentanoid terpene biosynthesis in a phasmid insect and in catmint.

The stick insect, Anisomorpha buprestoides, and the catmint, Nepeta cataria, produce closely related cyclopentanoid terpenes, anisomorphal and nepetalactone. Tracer experiments with isotopes indicate that anisomorphal is synthesized by the walking stick from normal terpene precursors (acetate or mevalonate). In the catmint plant, isolated leaf disks synthesized nepetalactone, utilizing the same precursors.

Major components in the exocrine secretion of a male butterfly (lycorea).

Extracts of the extrusible secretion-disseminating organs ("hairpencils") of the male of the danaid butterfly, Lycorea ceres ceres, from Trinidad, contain a pyrrolizidine and two aliphatic esters. An odorous component, present in trace amounts, remains unidentified. Judging from the function of "hairpencils" in a related species, the secretion may play a mediating role in courtship.

Defensive use by an insect of a plant resin.

Larvae of the sawfly Neodiprion sertifer (Hymenoptera: Diprionidae), when disturbed, discharge an oily oral effluent essentially identical chemically to the terpenoid resin of its host plant (Pinus sylvestris). The resin is sequestered by the larva upon feeding, and stored in two compressible diverticular pouches of the foregut. The fluid is effectively deterrent to predators. The defensive use by an insect of a plant resin provides an instance of secondary utilization by a herbivore of the protective chemical weaponry of its host.

Inhalational anesthetics stereochemistry: optical resolution of halothane, enflurane, and isoflurane.

Halothane (I), enflurane (II), and isoflurane (III), which are among the most important inhalation anesthetics, are currently administered as racemic mixtures. The pure enantiomers have not been described, and no analytical method for resolving the commercially available racemic mixtures has been reported. Complete optical resolution of (+/-)-I and (+/-)-III on per-n-pentylated alpha-cyclodextrin (Lipodex A) and of (+/-)-II and (+/-)-III on octakis(6-O-methyl-2,3-di-O-pentyl)-gamma-cyclodextrin capillary columns has been achieved, making rapid and convenient determination of enantiomeric ratios in samples of all three of these anesthetics possible.

Combinatorial chemistry in insects: a library of defensive macrocyclic polyamines.

The pupal defensive secretion of the coccinellid beetle Epilachna borealis is composed principally of a combinatorial library of macrocyclic polyamines. These compounds constitute a previously unrecognized family of natural products, characterized by extremely large-ring lactonic structures derived from a small set of (2-hydroxyethylamino)alkanoic acids. The combinatorial assembly of these simple building blocks generates a high degree of structural diversity, which is further increased by slow, spontaneous intramolecular rearrangement of the macrocycles.

Polyzonimine: A novel terpenoid insect repellent produced by a milliped.

A nitrogen-containing terpene 6,6-dimethyl-2-azaspiro[4.4]non-1-ene (polyzonimine) was isolated from the defensive secretion of the milliped Polyzonium rosalbum. Polyzonimine, which is repellent to such natural enemies of the milliped as ants, acts as a topical irritant to insects (10-4 M induces scratching in cockroaches). Its structure was confirmed by a five-step synthesis starting from 2,2-dimethyl-7-oxabicyclo[4.1.0]heptane.

Stink of Stinkpot Turtle Identified: ohgr-Phenylalkanoic Acids.

The exocrine secretion of the "stinkpot turtle," Sternotherus odoratus, discharged by the animals in response to disturbance, contains four omega-phenylalkanoic acids (phenylacetic, 3-phenylpropionic, 5-phenylpentanoic, and 7-phenylheptanoic). The last two of these are new natural products. The first two are powerfully malodorous and responsible for the stench of the fluid. Lesser components, including several aliphatic acids, are also present. Only a few milligrams of secretion are discharged by a turtle at any one time. Although bioassays with fish suggest that the secretion has the potential to serve as a feeding deterrent to predators, it is argued that Sternotherus does not ordinarily discharge enough fluid to effect this action and may employ its secretion only as an aposematic signal that warns predators of its more generalized undesirability.

Scent organ development in creatonotos moths: regulation by pyrrolizidine alkaloids.

7-Hydroxy-6,7-dihydro-5H-pyrolizine-1-carboxaldehyde is the major volatile component of the scent organs in males of two species of Creatonotos (Lepidoptera, Arctiidae). The biosynthesis of this presumed pheromone depends on the presence of pyrrolizidine alkaloids in plants that are ingested by the larvae. In addition, these secondary plant substances control the morphogenesis of the scent organs. This morphogenetic effect of an alkaloid has not been observed previously.

Sex pheromone of the winter moth, a geometrid with unusually low temperature precopulatory responses.

The sex pheromone for the winter moth, Operophtera brumata (L.), has been identified as the novel compound (Z,Z,Z)-1,3,6,9-nonadecatetraene. The male moths respond to the pheromone at low temperatures (4 degrees to 15 degrees C) and exhibit an upper response limit that coincides with the lower response limit for other reported moth sex pheromone systems. The pheromone attracted two other geometrid species, O. bruceata (Bruce spanworm) and O. occidentalis.

Chiral silylation reagents for the determination of absolute configuration by NMR spectroscopy.

We have investigated the use of chiral silylating reagents as analytical probes for determining the absolute stereochemistry of natural products by NMR spectroscopy. These reagents are prepared in high chemical yield in one step and can be used to derivatize chiral allylic alcohols which are incompatible with ester-based methodologies. Microscale ( approximately 400 nmol) derivatization conditions have been defined. The resulting siloxane diastereomers are readily distinguished by their (1)H NMR spectra.