Oviposition-stimulatory activity of phenanthroindolizidine alkaloids of host-plant origin to a danaid butterfly, Ideopsis similis

Oviposition response of Ideopsis similis (L.) (Lepidoptera: Danaidae) was examined for 12 phenanthroindolizidine alkaloids present in its host plant, Tylophora tanakae (Maxim.) (Asclepiadaceae). At least five alkaloids, i.e. (+)‐isotylocrebrine (3,4,6,7‐tetramethoxyphenanthroindolizidine; l ), (+)‐3‐demethyliso‐ tylocrebrine ( 3 ), (+)‐isotylocrebrine N‐oxide ( 5 ), (+)‐6‐demethyltylocrebrine ( 8 ) and (–)‐7‐demethyltylophorine ( 10 ), were found to individually stimulate oviposition by females. Of these, compounds 1, 3 and 10 were regarded as key components most responsible for host recognition or preference. However, female egg‐laying was much higher in response to a mixture of the five alkaloids. In two‐choice bioassays, more eggs were deposited on samples comprising the five alkaloids than on samples consisting of a single alkaloid. This suggests strongly that host selection by the butterfly is mediated by the synergistic action of several phenanthroindolizidine alkaloids present in the host plant.     

Alkaloids from the hallucinogenic plant Virola sebifera

Bark of Virola sebifera used in the preparation of hallucinogenic snuffs and drinks in Venezuela has yielded N-methyl-N-formyltryptamine and N-methyl-N-acetyltryptamine, which exist in two rotameric forms reflecting hindered rotation around the carbon—nitrogen bond of the amide function. They were detected by HPLC as well as NMR. 2-Methyl-1,2,3,4-tetrahydro-β-carboline, N,N-dimethyltryptamine, its oxide and N-monomethyltryptamine were also identified.     

Loline alkaloids: Currencies of mutualism

Several species of Lolium and other cool-season grasses (Poaceae subfamily Pooideae) tend to harbor symbiotic, seed-transmitted, fungi that enhance their fitness by various means. These fungal endophytes--species of Neotyphodium or Epichlo? (Clavicipitaceae)--are known for production of antiherbivore metabolites such as the bioprotective loline alkaloids. Lolines are saturated pyrrolizidines with an exo-1-amine and an ether bridge between C-2 and C-7. The ether bridge is an unusual feature for a biogenic compound in that it links two bridgehead carbon atoms. Much of the loline-biosynthetic pathway has been elucidated by administering isotopically labeled precursors to fungal cultures and by comparisons of loline biosynthesis genes to known gene families. The first step appears to be an unusual gamma-substitution reaction involving an enzyme related to O-acetylhomoserine (thiol) lyase, but which uses the secondary amine of L-proline rather than a sulfhydryl group as the nucleophile. The strained ether bridge is added after formation of the pyrrolizidine rings. Lolines with dimethylated or acylated 1-amines have insect antifeedant and insecticidal activities comparable to nicotine, but little or no toxicity to mammals. Considering the surprising abundance of lolines in some grass-endophyte symbiota, possible additional effects on plant stress tolerance and physiology are worth future consideration. In this review, we discuss the history of loline discovery, methods of analysis, biological activities and distribution in nature, as well as progress on the genetics and biochemistry of their biosynthesis, and on the chemical synthesis of these alkaloids.     

Pyrrolizidine alkaloids in the antipodean genus Brachyglottis (Asteraceae)

The phylogeny of the genus Brachyglottis suggests that its constituent species should contain pyrrolizidine alkaloids. Consistent with this hypothesis, and the established occurrence of such alkaloids in Brachyglottis repanda, Brachyglottis kirkii, and Brachyglottis hectori, an investigation of Brachyglottis adamsii revealed the presence of senecionine and retrorsine; Brachyglottis huntii was found to contain senkirkine and retrorsine; 7-O-angelylheliotridine was the predominant alkaloid in Brachyglottis perdicioides, and the same alkaloid together with senecionine, senkirkine and intergerrimine was present in the Brachyglottis hectori × B. perdicioides “Alfred Atkinson” horticultural hybrid; Brachyglottis sciadophila contained clivorine and neopetasitenine (acetylfukinotoxin); the latter alkaloid was also present in B. kirkii together with the previously reported senkirkine and senkirkine 12-acetate.     

Monomeric and Dimeric 9‐O Anthraquinone and Phenanthryl Derivatives of Cinchona Alkaloids as Chiral Solvating Agents for the NMR Enantiodiscrimination of Chiral Hemiesters

Mono‐ and bis‐alkaloid chiral auxiliaries with anthraquinone or phenanthryl cores were probed as chiral solvating agents (CSAs) for the enantiodiscrimination of chiral cyclic hemiesters. The dimeric anthraquinone derivative and the monomeric phenanthryl one showed remarkable efficiency in the nuclear magnetic resonance (NMR) differentiation of enantiomeric mixtures of hemiesters. An anthraquinone analogous with a single alkaloid unit was remarkably less effective. The conformational prevalence of the chiral auxiliaries were ascertained by NMR. Chirality 27:693–699, 2015. © 2015 Wiley Periodicals, Inc.