排序方式: 共有38条查询结果,搜索用时 15 毫秒
21.
建立了蜂蜜中5种吡咯里西啶类生物碱的超高效液相色谱-串联质谱测定方法.蜂蜜样品用50%甲醇超声提取,强阳离子交换固相萃取柱净化富集,超高效液相色谱-三重四极杆串联质谱MRM模式检测,外标法定量.以Waters BEH C18(100 mm×2.1 mm,1.7μm)色谱柱分离,以含0.1%甲酸的乙腈和0.1%甲酸水溶液进行梯度洗脱.倒千里光碱、千里光宁、千里光菲啉和野百合碱在0.2—100.0μg·kg-1,克氏千里光宁在1.0—200.0μg·kg-1的浓度范围内各化合物线性关系良好,相关系数r均大于0.999,定量限在0.2—0.8μg·kg-1之间.在3个加标水平下,空白基质蜂蜜中的5种生物碱的平均回收率为82.0%—110.0%之间,相对标准偏差(RSD)小于12.5%.方法准确可靠,适合于蜂蜜中吡咯里西啶类生物碱的测定. 相似文献
22.
Summary. A widely distributed host race of Tyria jacobaeae lives on Senecio jacobaea and related species and accumulates pyrrolizidine alkaloids (“PA race”), another race, which is restricted to the Alps and
found on Petasites paradoxus, sequesters sesquiterpenes, such as petasol and isopetasol. Nucleotide sequences of the mitochondrial 16S rDNA gene show
1% sequence divergence, indicating that genetical differences exist between the PA exploiting and the terpene-sequestering
host races of T. jacobaeae. This finding suggests that both host races of T. jacobaeae must have been separated for some time already, possibly since the Pleistocene.
Received 2 May 2001; accepted 1 June 2001. 相似文献
23.
Thomas Hartmann Claudine Theuring Till Beuerle Elizabeth A. Bernays 《Chemoecology》2004,14(3-4):207-216
Summary. The alkaloid profiles of the life history stages
of the highly polyphagous arctiid Estigmene acrea were
established. As larvae individuals had free choice between
a plain diet (alkaloid-free) and a diet that was supplemented
with Crotalaria-pumila powder with a known content and
composition of pyrrolizidine alkaloids (PAs). Idiosyncratic
retronecine esters (insect PAs) accounted for approximately
half of the PAs recovered from the larvae. These alkaloids
were synthesized by the larvae through esterification of dietary
supinidine yielding the estigmines, and esterification of
retronecine yielding the creatonotines. The retronecine is
derived from insect-mediated degradation of the sequestered
pumilines (macrocyclic PAs of the monocrotaline type).
With one exception, the PA profiles established for larvae
were found almost unaltered in all life-stages as well as
larval exuviae and pupal cocoons. The exception is the
males, which in comparison to pupae and adult females,
showed a significantly decreased quantity of the creatonotines
and pumilines. These data support the idea that
the creatonotines are direct precursors of the PA-derived male
courtship pheromone, hydroxydanaidal. Crosses of PA-free
males with PA-containing females and vice versa confirmed
an efficient trans-mission of PAs from males to females and
then from females to eggs. In single cases a male bestowed
almost his total PA load to the female, and a female her total load
to the eggs. The results are discussed with respect to pheromone
formation, PA transmission between life-stages, and the
defensive role of PAs against predators and parasitoids 相似文献
24.
Alkaloid tolerance in Manduca sexta and phylogenetically related sphingids (Lepidoptera: Sphingidae) 总被引:2,自引:0,他引:2
Summary. Nicotine tolerance is well known for Manduca sexta. It also occurs in several other sphingids of the subfamilies Macroglossinae and Sphinginae. Only members of the subfamily
Smerinthinae appear to be more susceptible to nicotine intoxication. Phylogenetic trees have been reconstructed from mitochondrial
16S rDNA and nuclear DNA to map nicotine tolerance.?The nicotine binding site of both α-subunits of nicotinic acetylcholine receptors (nAChR) have been amplified and sequenced. No apparent amino acid substitution
can be seen in the putative nicotine binding site of the α-subunits of nAChR from nicotine tolerant and nicotine sensitive sphingids. Thus, a simple target-site modification can be
ruled out as a cause for nicotine tolerance. This finding agrees with feeding experiments: larvae of M. sexta and other sphingids of the Macroglossinae and Sphinginae not only tolerated nicotine, but also many other alkaloids that
affect neuroreceptors other than acetylcholine receptors (nAChR, mAChR).?Only 10 to 20% of nicotine injected into larvae of
nicotine-tolerant taxa could be recovered later as free nicotine, nicotine N-oxide or cotinine, i.e., 80 to 90% must have been converted to polar conjugates or degradation products which are not detectable with the methods
applied. Usually more than 98% of the recoverable alkaloids were found in the faeces. Excretion reached a maximum 6 h after
injection in tolerant taxa. Larvae of Manduca sexta, which were reared on a nicotine-rich diet, showed higher nicotine degradation and faster nicotine elimination than na?ve
larvae. Application of the cytochrome P450 inhibitor SKF 525A (proadifen) reduced the formation of nicotine N-oxide and the rate of alkaloid degradation. Thus, an
inducible detoxification mechanism, coupled with a rapid and inducible excretion, appear to be a strategy in Sphingidae that
helps them to live on host plants rich in otherwise toxic secondary metabolites.
Received 23 March 2001; accepted 4 August 2001. 相似文献
25.
Summary. Hydroxydanaidal, the pyrrolizidine alkaloid-derived male corematal pheromone active in the close-range precopulatory interactions
of the moth Utetheisa ornatrix, appears not to contribute to the chemical defense of this moth. The compound failed to manifest feeding deterrency as an
additive to mealworms, in assays with a lycosid spider (Lycosa ceratiola). Moreover, contact with the male’s coremata, such as appears to occur inevitably in consequence of courtship in Utetheisa, does not in itself reduce the palatability of the female moth. 相似文献
26.
Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis
and constraints on defence level during the seedling stage were examined
in the annual Senecio vulgaris and the monocarpic perennial
Senecio jacobaea. In both species, PAs were actively
synthesized from the onset of seedling growth so that juvenile stages
did not go through an undefended stage. Roots are known to be the
exclusive sites where PAs are produced. Root biomass was the single most
important biomass parameter explaining variation in total PAs per
seedling. All correlation coefficients between—relative growth
rate and PA concentration were negative, but none was significant.
However, a significant negative—correlation was found between
shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have
shown that the shoot to root ratio is positively correlated with
relative growth—rate of established S. jacobaea plants.
It is therefore suggested that young S. jacobaea plants
with a high shoot to root ratio and hence a high growth capacity
necessarily have lower PA defence levels than plants with a low
shoot to root ratio.
Received 10 July 2002; accepted 16 November 2002. 相似文献
27.
Summary Among alkaloids the pyrrolizidine alkaloids (PAs) play a unique role in the interactions between plants and adapted insects. InSenecio spp. (Asteraceae) PAs are synthesized in the roots as alkaloidN-oxides which are specifically translocated into shootsvia the phloem-path and channeled to the preferred sites of storage (e.g. inflorescences) where they are stored in the cell vacuoles. In differentSenecio spp. senecionineN-oxide is produced as the common product of biosynthesis, which subsequentlyvia a number of simple but specific reactions is transformed into typical speciesspecific PA-patterns. Insects from diverse taxa sequester PAs for their own defense. Lepidopterans (e.g. arctiids such asTyria jacobaeae andCreatonotos transiens) may hydrolyze plant acquired ester-PAs and convert the resulting necine base into insect-specific PAs by esterification with an acid of their own metabolism. Adapted arctiids and the grasshopperZonocerus take up PAs in the state of the tertiary amine.N-Oxides are reduced in the guts prior to uptake. In the bodies the tertiary PAs are rapidlyN-oxidized by a specific mixed-function oxigenase and are maintained in theN-oxide state. The importance of the reversible interconversion of the nontoxicN-oxide (pro-toxine) into the toxic tertiary alkaloid is discussed as the specific feature of PAs in plant-insect interactions. 相似文献
28.
Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range. 相似文献
29.
Thomas?HartmannEmail author H?kan?H?ggstr?m Claudine?Theuring Rainer?Lindigkeit Martine?Rahier 《Chemoecology》2003,13(3):123-127
Summary. The harvestman Mitopus morio (Phalangidae) is
a generalist predator. It is known to prey on larvae of the
chrysomelid leaf beetle Oreina cacaliae defended by plant
acquired pyrrolizidine alkaloids (PAs). Tracer feeding
experiments were performed to determine how harvestmen
tolerate protoxic PAs. Minced meat containing either
[14C]senecionine or [14C]senecionine N-oxide was fed to
M. morio and subsequently feces and bodies were analyzed.
Labeled alkaloid N-oxide remained stable and was eliminated
almost unaltered with the feces; only 10% was recovered
as tertiary PA. In contrast, approximately 80% of
labeled tertiary alkaloid (senecionine) ingested with the diet
was N-oxidized and eliminated; the remaining 20% consisted
of unchanged senecionine and a polar metabolite
of unknown structure. Harvestmen process their diet by
excreting digestive juice, indicated by bleaching of the meat
color. Analysis of the processed diet revealed some N-oxidation
of [14C]senecionine, suggesting the gut as the site of Noxidation.
Analysis of the bodies of harvestmen 80 hours
after the tracer feeding pulse revealed only trace amounts of
the polar metabolite. Neither senecionine nor its N-oxide
could be detected in the body extracts. The results are discussed
in relation to the strategies of PA adapted insects to
avoid accumulation of tertiary PAs in living tissues. 相似文献
30.
D. Wianowska S. Garbaczewska A. Cieniecka–Roslonkiewicz R. Typek A. L. Dawidowicz 《Chemistry and Ecology》2018,34(6):582-594
This study discusses the similarities and differences between the antifungal activity of Chelidonium majus L. extracts and chelerythrine/sanguinarine, the main alkaloids in these extracts, against the plant pathogenic fungus, Botrytis cinerea. The obtained data show that the Ch. majus L. extracts inhibit the growth of B. cinerea very effectively. The extracts activity is significantly greater than that of chelerythrine/sanguinarine standard solutions alone and it does not always reflect the total content of alkaloids in the extracts. It has been proved that B. cinerea exhibits very diverse resistance to chelerythrine and sanguinarine. The IC50 values for chelerythrine and sanguinarine equal 5.41?mg/mL and 1.76?mg/mL, respectively. In the mixture the antifungal activity of chelerythrine and sanguinarine is antagonistic in the concentration dependent way. Based on the presented data it is not clear, however, which alkaloids present in the Ch, majus extracts at significantly lower concentration levels enhance the activity of chelerythrine and sanguinarine so that the extracts activity is considerably greater than that of both main alkaloids mixtures. 相似文献