Lacinilene C,A revised structure,and lacinilene C 7-methyl ether from Gossypium bracts

Two sesquiterpenes, which exhibit brilliant yellow fluorescence in the ultraviolet, have been isolated from frost-killed cotton bracts. They have been identified as lacinilene C and its 7-methyl ether. A revised structure related to the cadinane ring system is proposed for lacinilene C.     

A possible relationship between phytoalexin production in the cotton leaf and a phytotoxic response

A 10-day time-course study on the production of 2,7-dihydroxycadalene, 2-hydroxy-7-methoxycadalene, lacinilene C and lacinilene C 7-methyl ether in cotton leaves induced by cell-free mycelial extracts of Aspergillus flavus showed that the cadalenes and the lacinilenes accumulate in a cyclic fashion. The initial increase at 2 days is followed by a greater increase at 6 days after treatment. The location of these compounds was found predominately either in a 6 mm wounded, treated area or in a 3 mm area immediately surrounding the 6 mm treated area of the leaf. Lacinilene C and lacinilene C 7-methyl ether were both phytotoxic in a Lemna minor bioassay. Endogenous constituents produced by plant cell damage could have triggered the production of the cadalenes and lacinilenes observed.     

Effects of methyl jasmonate on phytoalexin production and aflatoxin control in the developing cotton boll

Artificially wounded 22–27-day old developing cotton bolls were initially inoculated with, (1) a cell-free, hot water-soluble mycelial extract (CFME) of an atoxigenic strain of Aspergillus flavus or with, (2) chitosan lactate (CHL) or with, (3) CFME or CHL and then exposed to gaseous methyl jasmonate (MJ) or, (4) exposed to MJ alone. Five days after these treatments, the induction of the sesquiterpenoid naphthol phytoalexins, 2,7-dihydroxycadalene (DHC) and 2-hydroxy-7-methoxy cadalene (HMC), lacinilene C, lacinilene C7-methyl ether, and the coumarin phytoalexin-scopoletin was determined on the excised carpel discs surrounding the inoculated surfaces of the developing cotton bolls. The results indicated a two- or three-fold increase in the production of the phytoalexins when gaseous MJ was added in combination to the CFME or the CHL elicitors. In a separate experiment, 22–27-day old developing cotton bolls were pretreated for a five-day period as described above and then a spore suspension of a toxigenic strain of A. flavus was introduced into a second artificial wound which was produced adjacent to the first wound. On boll maturity, the cottonseeds located within the locules underlying the areas that were pretreated with both elicitors and MJ then later infected with toxigenic A. flavus exhibited a 75–95% aflatoxin B₁ inhibition. These results suggest a host defense mechanism which may be triggered by both elicitors and MJ.     

6-Hydroxy- and 6-methoxyflavonoids from Neurolaena lobata and N. macrocephala

Twelve flavonoids including one new sulfate were isolated from Neurolaena lobata, and six known flavonoids were obtained from N. macrocephala. The new compound isolated from N. lobata is 6-hydroxykaempferol 3-methyl ether 7-sulfate, and the known flavonoids are 6-hydroxykaempferol 3,7-di-dimethyl ether, 6-hydroxykaempferol, 3-methyl ether 7-glucoside, 6-hydroxykaempferol 7-glucoside, quercetagetin and its 7-glucoside, quercetagetin 3,6- and 3,7-dimethyl ethers, quercetagetin 3-methyl ether 7-glucoside and 7-sulfate, 6-hydroxyluteolin 3′-methyl ether and 6-hydroxyluteolin 7-glucoside. The known flavonoids identified from N. macrocephala are quercetagetin 3,6- and 3, 7-dimethyl ethers, quercetagetin 6-methyl ether 7-glucoside, quercetagetin 3,6-dimethyl ether 7-glucoside, quercetagetin 7-glucoside and quercetagetin 3-methyl ether 7-sulfate.     

New sesquiterpenoids of Bombax malabaricum

Hemigossypol-6-methyl ether, reported to be present in the root bark of Bombax malabaricum, has been shown to be isohemigossypol-1-methyl ether. Isohemigossypol-1,2-dimethyl ether, 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthaquinone, 7-hydroxycadalene and an unidentified phenolic compound have also been isolated. Long range couplings in the ¹H NMR spectrum of isohemigossypol-1-methyl ether have been established by decoupling experiments.     

3-Hydroxyisoflavanones from the stem bark of Dalbergia melanoxylon: Isolation,antimycobacterial evaluation and molecular docking studies

Two new 3-hydroxyisoflavanones, (S)-3,4′,5-trihydroxy-2′,7-dimethoxy-3′-prenylisoflavanone (trivial name kenusanone F 7-methyl ether) and (S)-3,5-dihydroxy-2′,7-dimethoxy-2″,2″-dimethylpyrano[5″,6″:3′,4′]isoflavanone (trivial name sophoronol-7-methyl ether) along with two known compounds (dalbergin and formononetin) were isolated from the stem bark of Dalbergia melanoxylon. The structures were elucidated using spectroscopic techniques. Kenusanone F 7-methyl ether showed activity against Mycobacterium tuberculosis, whereas both of the new compounds were inactive against the malaria parasite Plasmodium falciparum at 10 μg/ml. Docking studies showed that the new compounds kenusanone F 7-methyl ether and sophoronol-7-methyl ether have high affinity for the M. tuberculosis drug target INHA.     

(+)-Pinpollitol: A di-O-methyl d-(+)-chiro-inositol from Pinus radiata

(+)-Pinpollitol, a new cyclitol recently isolated from the pollen of Pinus radiata, was found in the needles of this species. (+)-Pinpollitol was found to be a di-O-methyl ether Of d-(+)-chiro-inositol, and tentative isomeric structures have been proposed for the cyclitol. (+)-Pinpollitol is the first di-O-methyl inositol to be found in a gymnosperm and is one of only three di-O-methyl inositols yet found in nature.     

Bacteriostatic heterocycles from Euodia lunu-ankenda

A new constituent characterized as 8-acetyl-3,4-dihydroxy-5,7-dimethoxy-2,2-dimethylchroman has been isolated together with alloevodionol-7-methyl ether, 4-methoxy-1-methyl-2(1H)quinolinone, evolitrine, isoevodionol and its methyl ether from the aerial parts of Euodia lunu-ankenda. Its structure was confirmed by its transformation to alloevodionol-7-methyl ether. 4-Methoxy-1-methyl-2(1H)quinolinone and its isomer were synthesized by a modified procedure.     

Spongiacidin C,a pyrrole alkaloid from the marine sponge Stylissa massa,functions as a USP7 inhibitor

USP7, a deubiquitylating enzyme hydrolyzing the isopeptide bond at the C-terminus of ubiquitin, is an emerging cancer target. We isolated spongiacidin C from the marine sponge Stylissa massa as the first USP7 inhibitor from a natural source. This compound inhibited USP7 most strongly with an IC₅₀ of 3.8 μM among several USP family members tested.     

On the natural occurrence of gossypetin 7- and 8-monomethyl ethers

The 7-methyl ether of gossypetin occurs, as a mixture of 4 glycosides, in the yellow inflorescence of Eriogonum nudum. In contrast to previous reports, however, it does not occur in Lotus corniculatus flowers, nor is it present in leaves of Medicago sativa. The 8-methyl ether, which is present in Lotus flowers, has been found for the first time in the Compositae, in flowers of Geraea canescens.     

Sexangularetin 3-glucoside-7-rhamnoside from gossypium hirsutum

A new diglycosylated flavonol was isolated from immature flower buds of the cotton plant Gossypium hirsutum. The structure was determined to be the 3-glucoside-7-rhamnoside of 3,5,7,4′-tetrahydroxy-8-methoxyflavone.     

Flavans from Zephyranthes flava

A new optically active flavan aglucone, 7-hydroxy-3′,4′-methylenedioxyflavan, and its 7-glucoside have been isolated from the bulbs of Zephyranthes flava, collected at flowering. Additionally, two known flavans, 7,4′-dihydroxy-3′-methoxyflavan and 7-methoxy-2′-hydroxy-4′,5′-methylenedioxyflavan, have been isolated for the first time from this species. The structures of these flavans have been established by comprehensive analyses (UV, IR, ¹H NMR, ¹³C NMR, mass spectrometry, [α]_D) of the compounds and their acetates, and also by chemical correlation.     

The Structure of a New Biflavone from Podocarpus fleuryi

Continuing the former report, another new minor biflavone was isolated. Its structure was assigned as robustaflavone-7-methyl ether (Ⅰ)by means of chemical reaction and lower shift of acetylation in 1HNMR.     

Flavonoids from Wyethia glabra

Ten flavonoid compounds, including three new natural products, were isolated from a dichloromethane extract of Wyethia glabra. The known compounds are: orobol 7-methyl ether, orobol 3′-methyl ether, naringenin 7-methyl ether, eriodictyol, 8-C-prenyleriodictyol, 6-C-prenyleriodictyol and 8-C-prenylnaringenin. Eriodictyol 7-methyl ether, 2′,4′,6′-trihydroxy-4-methoxychalcone and 6-C-prenylnaringenin are new natural products. An additional prenylated flavanone was isolated and partially characterized.     

Methylated 7-deazahypoxanthines as regiochemical probes of xanthine oxidase

7-Deazahypoxanthine was found to be oxidised by cow's milk xanthine oxidase exclusively at carbon 2. The resulting 7-deazaxanthine is a strong inhibitor of the enzymatic reaction. This offers a possibility for determining the structural requirements of ligand binding separately for the first step. All the monomethyl isomers of 7-deazahypoxanthine were tested as probes by measuring their Km, Ki and V values. While the N-3-methyl and C-7-methyl isomers are still processed, the N-9-methyl and 6-O-methyl isomers are bound as inhibitors to the active site. The N-1-methyl compound is neither an inhibitor nor a substrate. This demonstrates that HN(1) and O = C(6) are essential for the binding. Replacement of O = C(6) by S = C(6) changes the substrate into a strong inhibitor (Ki = 9 microM), implying that the electron transfer to the enzyme is hindered. Methylation of the thioxo group (S =) reduces the inhibition significantly. In contrast to 7-deazahypoxanthine, 2-thioxo-7-deazaxanthine is an activator at concentrations below 87 microM and a partial competitive inhibitor above this concentration, which implies the presence of a second binding site.     

棉花苞叶光呼吸和PSII热耗散对土壤水分的响应

在新疆气候生态条件下, 采用膜下滴灌植棉技术, 设置不同滴灌水分处理, 研究了不同滴灌量条件下棉花(Gossypium hirsutum)苞叶和叶片碳同化、光呼吸作用、光系统II (PSII)热耗散作用及其光破坏防御机制的差异, 以揭示滴灌节水条件下棉花苞叶缓解光抑制的机理及与棉花抗旱特性的关系。结果表明: 棉花开花后苞叶及叶片在高温强光下实际光化学效率(Φ_PSII)显著降低, 发生明显的光抑制现象, 但苞叶的光抑制程度较叶片轻; 与正常滴灌量处理相比, 节水滴灌条件下棉花水分亏缺, 叶片净光合速率(P_n)、Φ_PSII、光呼吸(P_r)、光化学猝灭系数(q_P)降低, 非光化学猝灭系数(NPQ)升高, 叶片光抑制程度加重, 而苞叶P_n、Φ_PSII、P_r、q_P、NPQ变化不大, 与正常滴灌量处理相比, 光抑制程度无显著差异。苞叶光呼吸速率与光合速率的比值(P_r/P_n)显著高于叶片; 滴灌节水条件下棉花适度水分亏缺对苞叶光呼吸及P_r/P_n无显著影响。高温强光下, 棉花节水滴灌对叶片PSII量子产量的转化与分配影响显著, 但对苞叶的影响不显著; 苞叶非调节性能量耗散的量子产量(Y(NPQ))高于叶片, 因此能有效地将PSII的过剩光能以热的形式耗散。综上所述, 与叶片相比, 苞叶对轻度水分亏缺不敏感, 是棉花适应干旱逆境较强的器官, 苞叶光呼吸和热耗散作用对光破坏防御具有重要意义。     

Detection of the chirality of C alpha-methylated alpha-amino acids with a dynamic helical poly(phenylacetylene) bearing aza-18-crown-6 ether pendants

A stereoregular poly(phenylacetylene) bearing the aza-18-crown-6 ether pendants (poly-1) was found to form a predominantly one-handed helix upon complexation with optically active C(alpha)-methylated alpha-amino acids and their amide derivatives including typical meteoritic C(alpha)-methylated alpha-amino acids such as C(alpha)-methyl norvaline and C(alpha)-methyl valine. The complexes exhibited an induced circular dichroism (ICD) in the UV-visible region of the polymer backbone. Therefore, poly-1 can be used as a novel probe for detection of the chirality of C(alpha)-methylated alpha-amino acids. The effect of the enantiomeric excess (ee) of C(alpha)-methylated alpha-amino acids on the helicity induction in poly-1 was also investigated.     

Transport of Radioactivity in Relation to Bracts in the Cotton Plant

[¹⁴C]sucrose was applied to the leaf subtending 14-d-old boll(cotton fruit) with and without bracts, and to bracts alonein var. Suvin (Gossypium barbadense L.). The removal of bractssubstantially enhanced the transport of radioactivity from theleaf to the carpels and seed cotton. When bracts alone weretreated, still larger quantities of radioactivity were incorporatedin the carpels and seed cotton. The bracts appeared to nourishthe developing boll through their own photosynthate and regulatethe transport of assimilate from the leaf. Radioactivity, transport, bracts, boll, carpels, seed cotton     

Trypanocidal activity of Lychnophora staavioides Mart. (Vernonieae, Asteraceae)

In the continuing search for new compounds with trypanocidal activity for use in blood banks to prevent the transmission of Chagas' disease, a trypanocidal extract of Lychnophora staavioides Mart. (Vernonieae, Asteraceae) was fractionated using several chromatographic techniques and afforded the following flavonoids: tectochrysin, pinostrobin, pinobanksin, pinobanksin 3-acetate, pinocembrin, chrysin, galangin 3-methyl ether, quercetin 3-methyl ether, chrysoeriol and vicenin-2. The most active compound was quercetin 3-methyl ether, which showed no blood lysis activity and which represents a promising compound for use against T. cruzi in blood banks.     

Photodynamic activity of anthraquinones isolated from Heterophyllaea pustulata Hook f. (Rubiaceae) on MCF-7c3 breast cancer cells

Searching for agents that could be effective in the treatment of cancer, special highlight has focused on the study of numerous plant-derived compounds. We previously demonstrated that anthraquinones (AQs) isolated from a vegetal species: Heterophyllaea pustulata Hook f. (Rubiaceae), such as rubiadin, rubiadin-1-methyl ether, soranjidiol, soranjidiol-1-methyl ether exhibit photosensitizing properties without antecedents as photodynamic agents in malignant cells. In the present study, we investigated the potential role of these AQs as a phototoxic agent against human breast carcinoma using MCF-7c3 cells. All AQs exhibited significant photocytotoxicity on cancer cells at the concentration of 100 μM with 1 J/cm² light dose, resulting soranjidiol-1-methyl ether in complete cell destruction. The observed cellular killing by photoactivated AQs exhibited close relation with singlet oxygen production, except for soranjidiol-1-methyl ether, where cell viability decrease is in relation to uptake by tumor cells.