高效液相色谱-高分辨质谱法鉴定拉萨大黄化学成分

建立了高效液相色谱-高分辨质谱法分析鉴定拉萨大黄化学成分。选用Agilent Zorbax SB-C18柱（150 mm×4.6 mm×5 μm）,以乙腈和水为流动相进行梯度洗脱,流速0.5 mL/min;采用电喷雾离子源,在正、负离子模式下对拉萨大黄提取物进行一级和多级全扫描质谱分析。综合分析化合物的色谱和质谱行为,并结合对照品、文献和数据库等相关数据鉴定化合物。在负离子模式下,鉴定出63种化合物;正离子模式下,鉴定出54种化合物。所检测到的化合物包括22种鞣质类、28种茋类、6种黄酮类、3种苯丙酸类、2种苯丁酮类和2种有机酸类,其中有53种化合物为在该药材中首次发现,且未发现蒽醌类成分。该方法快速、灵敏,不仅提高了拉萨大黄复杂基质中微量化合物的鉴定效率,同时实现了对拉萨大黄提取物中不同类型化合物的分析鉴别,为进一步阐明拉萨大黄的药效物质基础及质控标准提供了科学依据。     

New Eugenol Derivatives with Enhanced Insecticidal Activity

Eugenol, the generic name of 4-allyl-2-methoxyphenol, is the major component of clove essential oil, and has demonstrated relevant biological potential with well-known antimicrobial and antioxidant actions. New O-alkylated eugenol derivatives, bearing a propyl chain with terminals like hydrogen, hydroxyl, ester, chlorine, and carboxylic acid, were synthesized in the present work. These compounds were later subjected to epoxidation conditions to give the corresponding oxiranes. All derivatives were evaluated against their effect upon the viability of insect cell line Sf9 (Spodoptera frugiperda), demonstrating that structural changes elicit marked effects in terms of potency. In addition, the most promising molecules were evaluated for their impact in cell morphology, caspase-like activity, and potential toxicity towards human cells. Some molecules stood out in terms of toxicity towards insect cells, with morphological assessment of treated cells showing chromatin condensation and fragmentation, which are compatible with the occurrence of programmed cell death, later confirmed by evaluation of caspase-like activity. These findings point out the potential use of eugenol derivatives as semisynthetic insecticides from plant natural products.     

Metabolomics to Decipher the Chemical Defense of Cereals against Fusarium graminearum and Deoxynivalenol Accumulation

Fusarium graminearum is the causal agent of Fusarium head blight (FHB) and Gibberella ear rot (GER), two devastating diseases of wheat, barley, and maize. Furthermore, F. graminearum species can produce type B trichothecene mycotoxins that accumulate in grains. Use of FHB and GER resistant cultivars is one of the most promising strategies to reduce damage induced by F. graminearum. Combined with genetic approaches, metabolomic ones can provide powerful opportunities for plant breeding through the identification of resistant biomarker metabolites which have the advantage of integrating the genetic background and the influence of the environment. In the past decade, several metabolomics attempts have been made to decipher the chemical defense that cereals employ to counteract F. graminearum. By covering the major classes of metabolites that have been highlighted and addressing their potential role, this review demonstrates the complex and integrated network of events that cereals can orchestrate to resist to F. graminearum.     

Antioxidant activity screening of extracts from Sideritis species (Labiatae) grown in Bulgaria

Plant samples from several species and populations of the genus Sideritis (Labiatae) grown in Bulgaria (S scardica, S syriaca and S montana) were extracted with different solvents. Their antioxidant activities were determined by the β‐carotene bleaching test (BCBT), 2,2′‐diphenyl‐1‐picrylhydrazyl (DPPH^?) radical scavenging method and static headspace gas chromatography (HS‐GC) and compared with the antioxidant activity of two reference compounds of different polarity, viz butylated hydroxytoluene (BHT) and rosmarinic acid. The pure reference compounds were applied in a ten‐times lower concentration than the plant extracts. The highest antioxidant activity in the BCBT, close to that of BHT, was observed for the more apolar extracts. The inhibitory effect on β‐carotene bleaching of the polar extracts and rosmarinic acid was much lower than that of BHT. The inhibition of hexanal formation in bulk safflower oil by most of S syriaca and S scardica extracts was as effective as BHT but less so than rosmarinic acid. S montana extracts showed weak antioxidant or even pro‐oxidant properties. Extracts from butanol and from ethyl acetate and the total methanol extracts from all Sideritis plants studied showed a strong radical scavenging activity against DPPH^?, close to that of rosmarinic acid. S montana extracts were, as a whole, slightly weaker radical inhibitors than the extracts from the other two species. The antioxidant activity of Sideritis extracts was attributed to the presence of flavonoid and phenylpropanoid glycosides. Copyright © 2003 Society of Chemical Industry     

Microbial Production of Natural and Unnatural Monolignols with Escherichia coli

Phenylpropanoids and phenylpropanoid-derived plant polyphenols find numerous applications in the food and pharmaceutical industries. In recent years, several microbial platform organisms have been engineered towards producing such compounds. However, for the most part, microbial (poly)phenol production is inspired by nature, so naturally occurring compounds have predominantly been produced to date. Here we have taken advantage of the promiscuity of the enzymes involved in phenylpropanoid synthesis and exploited the versatility of an engineered Escherichia coli strain harboring a synthetic monolignol pathway to convert supplemented natural and unnatural phenylpropenoic acids into their corresponding monolignols. The performed biotransformations showed that this strain is able to catalyze the stepwise reduction of chemically interesting unnatural phenylpropenoic acids such as 3,4,5-trimethoxycinnamic acid, 5-bromoferulic acid, 2-nitroferulic acid, and a “bicyclic” p-coumaric acid derivative, in addition to six naturally occurring phenylpropenoic acids.     

Inhibition of radish germination and root growth by coumarin and phenylpropanoids

Thirteen natural and synthetic phenylpropanoids as well as coumarin (2×10⁴M) were tested for their biological activity on radish germination and subsequent root growth in light and darkness. Coumarin was the most potent inhibitor. With some exceptions, phenylpropanoids with a carboxylic group in the side chain inhibited root growth. Coumarin was formed spontaneously by photooxidation of 2-hydroxycinnamic acid. Microscopic observations of root treated with coumarin suggest that this substance inhibits the elongation of cells of the differentiating zone of the root.     

Comparative Detoxification of Plant (Magnolia virginiana) Allelochemicals by Generalist and Specialist Saturniid Silkmoths

The foliage of sweetbay magnolia (Magnolia virginana) contains at least two biologically active phenylpropanoid compounds (magnolol and a biphenyl ether) that are toxic to a number of generalist insect herbivores. These compounds have little effect on caterpillars of the sweetbay silkmoth, C. securifera, which is a specialist on sweetbay, but they are toxic to two closely related silkmoths, C. angulifera and C. promethea. To understand the influence of phytochemistry on the evolution of host use and feeding specialization in Callosamia, the detoxification capability of C. securifera was compared with that of C. angulifera and C. promethea. Degradation of magnolol and the biphenyl ether by midgut homogenate of the sweetbay specialist was NADPH-dependent and inhibited by piperonyl butoxide, suggesting the involvement of cytochrome P-450 detoxification enzymes. Both were degraded three times faster in the specialist compared to the unadapted herbivores. Higher rates of degradation could not be induced in the polyphagous C. promethea by a mixture of magnolol and the biphenyl ether or by the P-450 inducer pentamethylbenzene, nor did activity vary significantly when larvae were reared on different host plants. Use of sweetbay by Callosamia silkmoths appears to be dependent on their ability to degrade host toxins rapidly via midgut detoxification enzymes. Moreover, the intraspecific comparisons contradict the common prediction that higher levels of cytochrome P-450 activity are found in more polyphagous species; instead, P-450 activity is more closely associated with specific chemical attributes of the herbivores' host plants.     

Glycine max signaling of environmental stress: Dynamics of inducible aromatic allelochemistry

Treatment of Davis soybeans (Glycine max (L.) Merrill) with a proven stress elicitor, iodoacetic acid, which binds specifically with sulfhydryl groups, induced a defensive phytochemistry, which included increased concentrations of aromatic compounds. High-performance liquid chromatography resolved groups of peaks, including one that contains the major allelochemical daidzein and several that contained relatively nonpolar compounds. Some peak groups were increased quantitatively, while others were decreased by iodoacetic acid elicitation. The more significant differences in methanol-extractable HPLC-resolved aromatic metabolites between elicited and nonelicitedG. max apical leaves occurred at 24, 48, and 72 hr after elicitation.