粗壮女贞中的新单萜配糖体(英)

从粗壮女贞（Ｌｉｇｕｓｔｒｕｍ ｒｏｂｕｓｔｕｍ）叶子中分离鉴定了４ 个新的单萜配糖体, 命名为粗壮女贞甙Ｄ、Ｇ、Ｈ和Ｌ． 通过波谱及化学方法,它们分别鉴定为香叶醇３′ＯαＬ吡喃鼠李糖基４′顺式香豆酰基βＤ吡喃葡萄糖甙（１） ,６羟基３,７二甲基２Ｅ,７葵二烯醇３′ＯαＬ吡喃鼠李糖基４′反式香豆酰基βＤ吡喃葡萄糖甙（２） ,６羟基３,７二甲基２Ｅ,７葵二烯醇３′ＯαＬ吡喃鼠李糖基４′顺式香豆酰基βＤ吡喃葡萄糖甙（３） 以及６,７二羟基３,７二甲基２Ｅ葵烯醇３′ＯαＬ吡喃鼠李糖基４′顺式香豆酰基βＤ吡喃葡萄糖甙（４） ． 此外,还从该植物得到了７ 个已知化合物,芹菜素（５）、ｃｏｓｍｏｓｉｉｎ（６） 、ｒｈｏｉｆｏｌｉｎ（７） 、山梨糖醇（８）、阿克苷（９） 、β谷甾醇（１０） 和齐墩果酸（１１） ．     

Survival of first instar larvae ofDanaus plexippus (Lepidoptera: Danainae) in relation to cardiac glycoside and latex content ofAsclepias humistrata (Asclepiadaceae)

Summary Our paper addresses field survivorship of first instar monarch butterfly larvae (Danaus plexippus L., Lep.: Danainae) in relation to the dual cardenolide and latex chemical defenses of the sand hill milkweed plant,Asclepias humistrata (Asclepiadaceae) growing naturally in north central Florida. Survival of first instar larvae in the field was 11.5% in the first experiment (15–20 April 1990), and dropped to 3.4% in the second experiment (20–30 April). About 30% of the larvae were found glued to the leaf surface by the milkweed latex. Predator exclusion of non-flying inverte-brates by applying tanglefoot to the plant stems suggested that the balance of the mortality was due to volant inverte-brates, or to falling and/or moving off the plants. Regression analyses to isolate some of the other variables affecting survivorship indicated that first instar mortality was correlated with (1) increasing cardiac glycoside concentration of the leaves, (2) increasing age of the plants, and (3) the temporal increase in concentration of cardiac glycosides in the leaves. The study also provided confirmatory data of previous studies that wild monarch females tend to oviposit onA. humistrata plants containing intermediate concentrations of cardiac glycosides. Cardiac glycoside concentration in the leaves was not correlated with that in the latex. The concentration of cardenolide in the latex is extremely high, constituting an average of 1.2 and 9.5% of the mass of the wet and dry latex, respectively. The data suggest that an increase in water content of the latex is compensated for by an influx of cardenolide with the result that the cardenolide concentration remains constant in the latex systems of plants that are growing naturally. We also observed first instar larvae taking their first bite of milkweed leaves in the field. In addition to confirming other workers findings that monarch larvae possess elaborate sabotaging behaviour of the milkweed's latex system, we discovered that several larvae on their first bite involuntarily imbided a small globule of latex and instantly became cataleptic. This catalepsis, lasting up to 10 min, may have been in response to the high concentration of cardenolide present in the latex ofA. humistrata, more than 10 times that in the leaves. The results of the present study suggest that more attention should be directed to plant chemical defenses upon initial attack by first instar insect larvae, rather than attempting correlations of plant chemistry with older larvae that have already passed the early instar gauntlet. The first bite of neonate insects may be the most critical moment for coping with the chemical defenses of many plants and may play a much more important role in the evolution of insect herbivory than has previously been recognized.     

The iridoid glycoside,catalpol, as a deterrent to the predatorCamponotus floridanus (Formicidae)

Summary We investigated the role of the iridoid glycoside, catalpol, as a deterrent to the predator,Camponotus floridanus. Four laboratory colonies of this ant were offered buckeye caterpillars (Junonia coenia: Nymphalidae) raised on diets with and without catalpol. The same colonies were offered sugar-water solutions containing varying concentrations of catalpol, in both no-choice and choice tests. Regardless of diet, buckeye caterpillars appeared to be morphologically protected from predation by the ants, possibly because of their large spines or tough cuticle. However, buckeyes raised on diets with catalpol had high concentrations of catalpol in their hemolymph; extracts of this high-catalpol hemolymph proved to be an effective deterrent to the ants. When starved ants were not given the choice of food items, they were more likely to consume sucrose solutions that contained 5 mg catalpol/ml or 10 mg catalpol/ml than they were to consume solutions with 20 mg catalpol/ml. When they were given a choice of sugar solution or a sugar solution containing catalpol, the ants avoided solutions with catalpol at any of these concentrations. Ant colony responses to catalpol in sucrose solutions varied considerably over time and among colonies.     

Two herbivore-deterrent iridoid glycosides reduce the in-vitro growth of a specialist but not of a generalist pathogenic fungus of Plantago lanceolata L

Summary. Many secondary plant compounds are involved in defense against both insect herbivores and pathogens. Two secondary plant compounds of Plantago lanceolata, the iridoid glycosides catalpol and its precursor aucubin, are well known for their deterrent effects on generalist and non-adapted specialist insect herbivores. We tested the effects of these compounds on the in-vitro growth of a specialist and generalist fungal pathogen of this host species. Two chemical forms of these iridoids were tested. The glycosides and their aglycones, the products of enzymatic conversion by specific $/Beta$-glucosidase enzymes. The glycosides enhanced growth of both the specialist fungus Diaporthe adunca and the generalist fungus Fusarium moniliforme var. subglutinans. The positive effect of these glycosides on the generalist fungus is in sharp contrast with the generally negative effects of these glysosides on generalist insect herbivores. The aglycones of aucubin and catalpol reduced the growth of the specialist fungus D. adunca, but, contrary to expectation, enhanced the growth of the generalist fungus F. moniliforme var. subglutinans. Effects of aucubin on D. adunca were stronger than effects of catalpol. This was true both for the growth stimulating effects of the glycosides and for the fungitoxic effects of the aglycones. We therefore expect that the effects of these iridoids in P. lanceolata on the specialist fungus will strongly depend on the ratio between catalpol and its precursor aucubin and the chemical form (glycoside or aglycone) in which these compounds are encountered by the fungus during growth. Our results suggest that iridoid glycosides in P. lanceolata can be used as defense against both herbivores and pathogens, but that their effects are highly specific with respect to the natural enemy species that is encountered. Received 11 April 2002; accepted 9 August 2002     

Responses of three mouse species to deterrent chemicals in the monarch butterfly. II. Taste tests using intact monarchs

Summary Peromyscus melanotis is the only one of three mouse species that eats monarch butterflies at their overwintering sites in Mexico. I tested two hypotheses: 1)P. aztecus avoids monarchs because of a bitter taste aversion to cardiac glycosides (CGs) and an inability to reject CG-rich body parts; 2)Reithrodontomys sumichrasti avoids monarchs principally because of a bitter taste aversion to the CGs. None of the species are sensitive to the toxic effects of ingested CGs. Feeding responses of laboratory-reared mice of each species to monarchs with low, medium and high CG concentrations were compared. BothP. aztecus andR. sumichrasti ate significantly fewer of all three types of monarchs thanP. melanotis. ForP. aztecus andR. sumichrasti, the number of monarchs eaten decreased with increasing CG concentration, whereas forP. melanotis, the number remained constant.Peromyscus melanotis andR. sumichrasti developed a feeding technique for rejecting the CG-laden cuticular material, which reduced the bitterness of ingested monarch material. However,R. sumichrasti displayed the technique significantly less often thanP. melanotis; andP. aztecus never developed it. I conclude that high taste sensitivity to CGs and less versatile food handling preventP. aztecus andR. sumichrasti from overcoming the monarch's chemical defenses.     

粗壮女贞中的新单萜配糖体

从粗壮女贞（Ｌｉｇｕｓｔｒｕｍ ｒｏｂｕｓｔｕｍ）叶子中分离鉴定了４个新的单萜配糖体,命名为粗壮女贞甙Ｄ、Ｇ、Ｈ和Ｌ．通过滤谱及化学方法,它们分别鉴定为香叶醇３‘－Ｏ－μ－Ｌ－南鼠李糖基－４’－顺式香豆酰基－β－Ｄ－吡喃葡萄糖甙（１）,６－羟基－３,７－二甲基－２Ｅ,７葵二烯醇３‘－Ｏ－α－Ｌ－吡喃鼠李糖基－４’反式香豆酰基－β－Ｄ－吡喃葡萄糖甙（２）,６－羟基－３,７－二甲基－２Ｅ,７－葵二烯醇     

Effectiveness of tiger moth (Lepidoptera, Arctiidae) chemical defenses against an insectivorous bat (Eptesicus fuscus)

Summary. Adult tiger moths exhibit a wide range of palatabilities to the insectivorous big brown bat Eptesicus fuscus. Much of this variation is due to plant allelochemics ingested and sequestered from their larval food. By using a comparative approach involving 15 species from six tribes and two subfamilies of the Arctiidae we have shown that tiger moths feeding on cardiac glycoside-containing plants often contain highly effective natural feeding deterrents. Feeding on pyrrolizidine alkaloid-containing plants is also an effective deterrent to predation by bats but less so than feeding on plants rich in cardiac glycosides. Moths feeding on plants containing iridoid glycosides and/or moths likely to contain biogenic amines were the least deterrent. By manipulating the diet of several tiger moth species we were able to adjust their degree of palatability and link it to the levels of cardiac glycosides or pyrrolizidine alkaloids in their food. We argue that intense selective pressure provided by vertebrate predators including bats has driven the tiger moths to sequester more and more potent deterrents against them and to acquire a suite of morphology characteristics and behaviors that advertise their noxious taste.     

Multi-level complexity in the use of plant allelochemicals by aposematic insects

Summary As recognized by Miriam Rothschild as early as the 1960s and repeatedly emphasized in her papers, the use, misuse, or non-use of plant allelochemicals by insects is extremely variable and difficult to predict, at many levels of time, space, and biological organization. Although certain patterns that reoccur have been important in the development of ecological theory, the optimization of cost-benefit equations involving two or three trophic levels, each with large numbers of individuals, populations, and species in erratic and complex interactions, produces unexpected and fascinating scenarios. The development of rapid colorimetric and chromatographic analyses for several types of plant allelochemicals, notably certain groups of alkaloids, cardiac and cyanogenic glycosides, phenolics, terpenes, and glucosinolates, has permitted a detailed investigation of the variation and flow of these substances in natural organisms and ecosystems. The results of these analyses, in our hands mostly for pyrrolizidine alkaloids (PAs), do not suggest a straightforward classical choice by the aposematic insect to simply sequester or synthesize its defences. Rather, they reveal a confusing variety of diffuse and complex patterns that become increasingly closer to chaos as they are multiplied across structures, species, sexes, stages, sites, seasons, and selective regimes. We present a model reflecting results of analyses at this chemoecological interface. Depending upon an initial option, involving the recognition (or not) of a plant allelochemical, the herbivore will face thereafter options to ingest it (or not), and then to tolerate and absorb (or detoxify and excrete), modify (or not), passively, actively or selectively accumulate, turn over (or not), distribute (or concentrate), and use this compound in a variety of growth, defense, or reproductive functions. The herbivore can also quantitatively or qualitatively regulate the intensity or dispersion of its attack on the plant tissues, in order to modify feedback loops of selection on the plant and its chemicals which exist in most of the earlier steps, or those with its predators and parasites that occur in the later ones. Options that lead to mutualism through positive feedback loops will tend to accumulate and become rapidly fixed by natural selection. Additional variations and anomalies such as automimicry, chemical mimicry, sexual dimorphism and communication, selective sequestration and passing-up of allelochemicals, special glands and structures, and synergism effects, are among the secondary complications of this model that have occupied much thought, time, experimental labor, and polemical space in chemical ecology journals and meetings. Examination of the tendencies and results at various points in the model can be used to explain these features and to make further predictions, plan experiments, and devise activity-based bioassays and new chemical analyses. These may lead some day to new and more robust visions of the major patterns of chemical transfer at this widespread and important natural interface.     

Milkweeds,monarch butterflies and the ecological significance of cardenolides

Summary The contribution of Miriam Rothschild to the monarch cardenolide story is reviewed in the light of the 1914 challenge by the evolutionary biologist, E.B. Poulton for North American chemists to explain the chemical basis of unpalatability in monarch butterflies and their milkweed host plants. This challenge had lain unaccepted for nearly 50 years until Miriam Rothschild took up the gauntlet and showed with the help of many able colleagues that monarchs are aposematically coloured because they sequester toxic cardenolides from milkweed host plants for use as a defence against predators. By virtue of Dr Rothschild's inspiration and industry, and subsequently that of Lincoln Brower and his colleagues, this tritrophic interaction has become a familiar paradigm for the evolution of chemical defences and warning colouration. We now know that the cardenolide contents of different milkweeds vary quantitatively, qualitatively and spatially, both within and among species and we are starting to appreciate the implications of such variation. However, as Dr Rothschild has pointed out in her publications, cardenolides have sometimes blinded us to reality and it is curious how little evidence there is for a defensive function to cardenolides in plants — especially against adapted specialists such as the monarch. Thus the review will conclude with a discussion of the significance of temporal variation and induction of cardenolide production in plants, the lethal plant defence paradox and an emphasis on the dynamics of the cardenolide-mediated interaction between milkweeds and monarch larvae.     

Molecular studies on the ouabain binding site of the Na+, K+-ATPase in milkweed butterflies

Summary. The Na⁺, K⁺-ATPase of the Monarch butterfly (Danaus plexippus) is insensitive to the inhibition by cardiac glycosides due to an amino acid replacement: histidine instead of asparagine at position 122 of the α-subunit representing the ouabain binding site. By PCR amplification of the DNA sequence of this site, a PCR product of 270 bp was obtained from DNA extracted from Danainae species (Danaus plexippus, D. chrysippus, D. gillipus, D. philene, D. genutia, Tirumala hamata, Euploea spp., Parantica weiskei, P. melusine), Sphingidae (Daphnis nerii) and mimics of milkweed butterflies (Hypolimnas missipus, Limenitis archippus and L. arthemis, Nymphalidae). Analysis of the nucleotide sequences revealed that the single point mutation in the ouabain binding domain (AAC-Asn for CAC-His) was present only in Danaus plexippus, but not in the other species investigated. Since these milkweed butterflies also store cardenolides, other structural modifications of the Na⁺, K⁺-ATPase may have occurred or other strategies of cardenolide tolerance have been developed. Received 15 May 2000; accepted 29 June 2000