Erigerol, a new labdane diterpene from Erigeron philadelphicus

Enantiospecific Entry to a Common Decalin Intermediate for the Syntheses of Highly Oxygenated Terpenoids

Herein, we describe an enantiospecific route to one enantiomer of a common decalin core that is present in numerous highly oxygenated terpenoids. This intermediate is accessed in eight steps from (R)-carvone, an inexpensive, enantioenriched building block, which can be elaborated to the desired bicycle through sequential Fe(III)-catalyzed reductive olefin coupling and Dieckmann condensation. The same synthetic route may be applied to (S)-carvone to afford the enantiomer of this common intermediate for other applications.

Terpenoids and Related Compounds from Plants of the Family Compositae (Asteraceae)

This review will summarize the authors’ studies on the structures of terpenoids and related compounds from plants of the family Compositae (Asteraceae). Eighty three new compounds have been obtained and characterized from seven species of the plants, namely, Erigeron annuus (L.) Pers., Erigeron philadelphicus L., Erigeron sumatrensis Retz., Ligularia dentata Hara, Ligularia stenocephala Matsum. et Koidz., Petasites japonicus Maxim. and Tussilago farfara L.

GC-MS Analysis, Antibacterial Activity and Genotoxic Property of Erigeron mucronatus Essential Oil

GC-MS analysis of the hydrodistilled oil of Erigeron mucronatus DC was carried out, after the separation of a crystalline compound, lachnophyllum cumulene. Twenty-four components were identified. The oil contained 59.6% sesquiterpenoids, 16.1% monoterpenoids and 24.3% polyacetylenic esters. Among the mono and sesquiterpenoids, limonene (10.3%) and caryophyllenes (11.4%) were the major constituents. The essential oil also revealed the unusual presence of both cis (8.3%) and trans (1.1%) methyl lachnophyllum esters. Seasonal variation in the yield of E. mucronatus oil was observed. The yield varied from 0.49 to 0.58%, being highest during the rainy season. Antimicrobial activity was assessed using a method based on zones of inhibition; the oil exhibited maximum anti- bacterial activity against both Staphylococcus aureus and Escherichia coli, but moderate activity against Pseudomonas aeruginosa. Genotoxicity of the oil was determined in AB blood serum at different concentrations and hours of exposure. The antibacterial activity of the oil and its insignificant genotoxicity at low concentrations make the oil a good candidate as a curative agent.

Two new cyclopentenone derivatives and a new cyclooctadienone derivative from Erigeron annuus (L.) PERS., Erigeron philadelphicus L., and Erigeron sumatrensis RETZ

Two new cyclopentenone derivatives, erigerenones A (1) and B (2), and a new cyclooctadienone derivative, erigerenone C (3), were isolated from the aerial parts of Erigeron philadelphicus L. Compound 2 was also isolated from the aerial parts of Erigeron annuus (L.) PERS. and Erigeron sumatrensis RETZ. The structures of 1-3 were elucidated on the basis of their spectral data.

Five new sesquiterpenoids and a new diterpenoid from Erigeron annuus (L.) PERS., Erigeron philadelphicus L. and Erigeron sumatrensis RETZ

The aerial parts of Erigeron annuus (L.) PERS., E. philadelphicus L. and E. sumatrensis RETZ. (Compositae) have been investigated chemically. A new sesquiterpenoid, 6beta,14-epoxyeudesm-4(15)-en-1beta-ol (1), and a new diterpenoid, philadelphinone (6), have been isolated from E. philadelphicus. Four new sesquiterpenoids, (7R*)-opposit-4(15)-ene-1beta,7-diol (2), 11-methoxyopposit-4(15)-en-1beta-ol (3), 15-methoxyisodauc-3-ene-1beta,5alpha-diol (4) and 10alpha-hydroxycadin-4-en-15-al (5), have been isolated from E. annuus. Compounds 2 and 4 were also isolated from E. sumatrensis. The structures of the new compounds were elucidated on the basis of their spectral data.

Grindelane diterpenoids from Stevia subpubescens

Four new 9R,13R-epoxylabdane diterpenes (1-4) and a known clerodane derivative, 3,4beta-epoxy-5beta,10beta-cis-17alpha, 20alpha-clerod-13(14)-en-15,16-olide, were isolated from the leaves of Stevia subpubescens. The structures, which correspond to the grindelane class of diterpenoids, were elucidated by NMR data, chemical correlation, and single-crystal X-ray diffraction analysis of monoacetate 5. The absolute configuration of 1-4 is based on the optical activity of ketone 3 as compared with data of closely related substances.

Insecticide synergists: role, importance, and perspectives

Synergists have been used commercially for about 50 years and have contributed significantly to improve the efficacy of insecticides, particularly when problems of resistance have arisen. In the current article we review the nature, mode of action, role in resistance management, natural occurrence, and significance in research of insecticide synergists. These natural or synthetic chemicals, which increase the lethality and effectiveness of currently available insecticides, are by themselves considered nontoxic. The mode of action of the majority of synergists is to block the metabolic systems that would otherwise break down insecticide molecules. They interfere with the detoxication of insecticides through their action on polysubstrate monooxygenases (PSMOs) and other enzyme systems. The role of synergists in resistance management is related directly to an enzyme-inhibiting action, restoring the susceptibility of insects to the chemical, which would otherwise require higher levels of the toxicant for their control. For this reason synergists are considered straightforward tools for overcoming metabolic resistance, and can also delay the manifestation of resistance. However, the full potential of these compounds may not have been realized in resistance management. Synergists have an important role to play in the ongoing investigation of insecticide toxicity and mode of action and the nature of resistance mechanism. They also can be used in understanding the effects of other xenobiotics in non-target organisms. The search for and the need of new molecules capable of synergizing existing or new pesticides has reactivated the identification and characterization of secondary plant compounds possessing such activity. Plants do possess and utilize synergists to overcome the damage produced by phytophages. This has to be exploited in pest management programs. Hopefully, it will lead to a new perspective on the nature and significance of synergism.