Recent advances in application and progress of advanced materials as adsorbents in sample preparation for plant growth regulators.

Plant growth regulators are a class of physiologically active substances that could modify or regulate basic physiological processes in the plant and defense against abiotic and biotic stresses, including natural plant growth regulators and synthetic ones. Different from natural plant growth regulators with low content and high cost of extraction in plants, synthetic ones can be produced in large-scale production and widely used in agriculture for increasing and securing yield and quality of the harvested produce. However, like pesticides, the abuse of plant growth regulators will have negative impacts on human beings. Therefore, it is important to monitor plant growth regulators residues. Due to the low concentration of plant growth regulators and complex matrices of food, it is necessary to isolate and extract plant growth regulators by appropriate adsorbents in sample preparation for obtaining satisfactory results. In the last decade, several advanced materials as adsorbents have shown superiority in sample preparation. This review briefly introduces the recent application and progress of advanced materials as adsorbents in sample preparation for extraction of plant growth regulators from the complex matrix. In the end, the challenge and outlook about the extraction of plant growth regulators of these advanced adsorbents in sample preparation are presented.

Main Allelochemicals from the Rhizosphere Soil of Saussurea lappa (Decne.) Sch. Bip. and Their Effects on Plants' Antioxidase Systems.

Allelochemicals are the media of allelopathy and form the chemical bases of plant-environment interactions. To determine true allelochemicals and their autotoxic effects, seven compounds were isolated and identified from in-situ sampled rhizosphere soil of cultivated Saussurea lappa. Of these; costunolide (2), dehydrocostus lactone (3) and scopoletin (4) showed significant inhibition on seedling growth in a concentration-dependent manner. Detection and observation demonstrated that the antioxidase system was found to be affected by these chemicals, resulting in the accumulation of ROS and membrane damage. To investigate their release ways, the compounds were traced back and volumes quantified in rhizosphere soil and plant tissues. This work made clear the chemical bases and their physiological effects on the plants. These chemicals were found to be the secondary metabolites of the plants and included in the rhizosphere soil. The findings identified a potential pathway of plant-plant interactions, which provided theoretical basis to overcoming replanting problems. This research was also useful for exploring ecological effects of allelochemicals in green agriculture.

Antifungal activity of umbelliferone derivatives: Synthesis and structure-activity relationships.

Umbelliferone was an important allelochemical with a wide spectrum bioactivity. In our previous study, C7 hydroxy in the backbone of umbelliferone was identified to be responsible for its phytotoxicity and the targeted modification of the above site could lead to the phytotoxicity loss. In view of this, a series of hydroxycoumarins and C7 O-substituted umbelliferone derivatives were efficiently synthesized to evaluate their antifungal activity against four phytopathogenic fungi. Most of them, as we predicted, exhibited improved fungicidal activity. The phytotoxicity of effective compounds was also assayed by Lactuca sativa to investigate their side effects on plant growth. Compounds 9 and 17 were identified to show strong antifungal activity with low phytotoxicity. A brief investigation on structure-activity relationships revealed that the modification at the C7 hydroxy of umbelliferone could be a promising way to enhance the antifungal activity with decreasing the phytotoxicity.

Synthesis of N-substituted phthalimides and their antifungal activity against Alternaria solani and Botrytis cinerea.

As organosulfur and organophosphorus agents, phaltane and phosmet are facing great challenges for the environmental contamination, mammalian toxicity and increasing resistance with long term use. It is efficient and meaningful to develop phthalimide-based alternatives with non-sulfur and non-phosphorus groups. A series of N-substituted phthalimides were synthesized and their antifungal activity against two disastrous phytopathogenic fungi, Alternaria solani and Botrytis cinerea was evaluated in vitro. Most of them showed significant antifungal activity against both of fungi, or either of them selectively. N-vinylphthalimide (4) and 8-[4-(phthalimide-2-yl) butyloxy] quinoline (13) were identified as the most promising candidates against B. cinerea and A. solani with the IC50 values of 7.92 µg/mL and 10.85 µg/mL respectively. The brief structure-activity relationships have revealed that vinyl, quinolyl, bromide alkyl and benzyl substitutions were appropriate substituents and coupling functional moieties indirectly with optimum alkyl chain was efficient to prepare phthalimides related fungicides.

Characterization of rhizosphere and endophytic fungal communities from roots of Stipa purpurea in alpine steppe around Qinghai Lake.

Stipa purpurea is among constructive endemic species in the alpine steppe on the Qinghai-Xizang Plateau. To reveal the fungal community structure and diversity in the rhizosphere and roots of this important grass and to analyze the potential influence of different habitats on the structure of fungal communities, we explored the root endophyte and the directly associated rhizosphere communities of S. purpurea by using internal transcribed spacer rRNA cloning and sequencing methods. We found that the roots of S. purpurea are associated with a diverse consortium of Basidiomycota (59.8%) and Ascomycota (38.5%). Most fungi obtained from rhizosphere soil in S. purpurea have been identified as Ascomycetes, while the high proportion detected in roots were basidiomycetous endophytes. The species richness, diversity, and evenness of fungal assemblages were higher in roots than in the rhizosphere soil. Fungi inhabiting the rhizosphere and roots of S. purpurea are significantly different, and the rhizosphere and endophyte communities are largely independent with little overlap in the dominant phyla or operational taxonomic units. Taken together, these results suggested that a wide variety of fungal communities are associated with the roots and rhizosphere soil of S. purpurea and that the fungal assemblages are strongly influenced by different habitats.

Phylogenic diversity and tissue specificity of fungal endophytes associated with the pharmaceutical plant, Stellera chamaejasme L. revealed by a cultivation-independent approach.

The fungal endophytes associated with medicinal plants have been demonstrated as a reservoir with novel natural products useful in medicine and agriculture. It is desirable to explore the species composition, diversity and tissue specificity of endophytic fungi that inhabit in different tissues of medicinal plants. In this study, a culture-independent survey of fungal diversity in the rhizosphere, leaves, stems and roots of a toxic medicinal plant, Stellera chamaejasme L., was conducted by sequence analysis of clone libraries of the partial internal transcribed spacer region. Altogether, 145 fungal OTUs (operational taxonomic units), represented by 464 sequences, were found in four samples, of these 109 OTUs (75.2 %) belonging to Ascomycota, 20 (13.8 %) to Basidiomycota, 14 (9.7 %) to Zygomycota, 1 (0.7 %) to Chytridiomycota, and 1 (0.7 %) to Glomeromycota. The richness and diversity of fungal communities were strongly influenced by plant tissue environments, and the roots are associated with a surprisingly rich endophyte community. The endophyte assemblages associated with S. chamaejasme were strongly shaped by plant tissue environments, and exhibited a certain degree of tissue specificity. Our results suggested that a wide variety of fungal assemblages inhabit in S. chamaejasme, and plant tissue environments conspicuously influence endophyte community structure.

Isolation and characterization of bacteria from the rhizosphere and bulk soil of Stellera chamaejasme L.

This study is the first to describe the composition and characteristics of culturable bacterial isolates from the rhizosphere and bulk soil of the medicinal plant Stellera chamaejasme L. at different growth stages. Using a cultivation-dependent approach, a total of 148 isolates showing different phenotypic properties were obtained from the rhizosphere and bulk soil. Firmicutes and Actinobacteria were the major bacterial groups in both the rhizosphere and bulk soil at all 4 growth stages of S. chamaejasme. The diversity of the bacterial community in the rhizosphere was higher than that in bulk soil in flowering and fruiting stages. The abundance of bacterial communities in the rhizosphere changed with the growth stages and had a major shift at the fruiting stage. Dynamic changes of bacterial abundance and many bacterial groups in the rhizosphere were similar to those in bulk soil. Furthermore, most bacterial isolates exhibited single or multiple biochemical activities associated with S. chamaejasme growth, which revealed that bacteria with multiple physiological functions were abundant and widespread in the rhizosphere and bulk soil. These results are essential (i) for understanding the ecological roles of bacteria in the rhizosphere and bulk soil and (ii) as a foundation for further evaluating their efficacy as effective S. chamaejasme growth-promoting rhizobacteria.

Tailoring 3,3'-dihydroxyisorenieratene to hydroxystilbene: finding a resveratrol analogue with increased antiproliferation activity and cell selectivity.

Four novel compounds were designed by "tailoring" 3,3'-dihydroxyisorenieratene (a natural carotenoid) based on an isoprene unit retention truncation strategy. Among them, the smallest molecule 1 (2,3,6,2',3',6'-hexamethyl-4,4'-dihydroxy-trans-stilbene) was concisely synthesized in a one-pot Stille-Heck tandem sequence, and surfaced as a promising lead molecule in terms of its selective antiproliferative activity mediated by blocking the NCI-H460 cell cycle in G1 phase. Additionally, theoretical calculations and cell uptake experiments indicate that the unique polymethylation pattern of compound 1 significantly induces a conformational change shift out of planarity and increases its cell uptake and metabolic stability. The observation should be helpful to rationally design resveratrol-inspired antiproliferative agents.

CuII ions and the stilbene-chroman hybrid with a catechol moiety synergistically induced DNA damage, and cell cycle arrest and apoptosis of HepG2 cells: an interesting acid/base-promoted prooxidant reaction.

Development of potential cancer treatment strategies by using an exogenous reactive oxygen species (ROS)-generating agent (prooxidant) or redox intervention, has attracted much interest. One effective ROS generation method is to construct a prooxidant system by polyphenolic compounds and Cu(II) ions. This work demonstrates that Cu(II) and the stilbene-chroman hybrid with a catechol moiety could synergistically induce pBR322 plasmid DNA damage, as well as cell cycle arrest and apoptosis of HepG2 cells. Additionally, an interesting acid/base-promoted prooxidant reaction was found. The detailed chemical mechanisms for the reaction of the hybrid with Cu(II) in acid, neutral and base solutions are proposed based on UV/Vis spectral changes and identification of the related oxidative intermediates and products.

Extraordinary radical scavengers: 4-mercaptostilbenes.

In the past decade, there was a great deal of interest and excitement in developing more active antioxidants and cancer chemoprevention agents than resveratrol, a naturally occurring stilbene. In this work, eight resveratrol-directed 4-mercaptostilbenes were constructed based on the inspiration that thiophenol should be a stronger radical scavenger than phenol, and their reaction rates with galvinoxyl (GO(.)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(.)) radicals in methanol and ethyl acetate were measured by using stopped-flow UV/Vis spectroscopy at 25 °C. Kinetic analysis demonstrates that 4-mercaptostilbenes are extraordinary radical scavengers, and the substitution of the 4-SH group for the 4-OH group in the stilbene scaffold is an important strategy to improve the radical-scavenging activity of resveratrol. Surprisingly, in methanol, some of the 4-mercaptostilbenes are 10(4)-times more active than resveratrol, dozens of times to hundreds of times more effective than known antioxidants (α-tocopherol, ascorbic acid, quercetin, and trolox). The detailed radical-scavenging mechanisms were discussed based on acidified-kinetic analysis. Addition of acetic acid remarkably reduced the GO(.) and DPPH(.) radical-scavenging rates of the 4-mercaptostilbenes in methanol, a solvent that supports ionization, suggesting that the reactions proceed mainly through a sequential proton loss electron transfer mechanism. In contrast, an interesting acid-promoted kinetics was observed for the reactions of the 4-mercaptostilbenes with DPPH(.) in ethyl acetate, a solvent that weakly supports ionization. The increased ratio in rates is closely correlated with the electron-rich environment in the molecules, suggesting that the acceleration could benefit from the contribution of the electron transfer from the 4-mercaptostilbenes and DPPH(.). However, the addition of acetic acid had no influence on the GO(.)-scavenging rates of the 4-mercaptostilbenes in ethyl acetate, due to the occurrence of the direct hydrogen atom transfer. Our results show that the radical-scavenging activity and mechanisms of 4-mercaptostilbenes depends significantly on the molecular structure and acidity, the nature of the attacking radical, and the ionizing capacity of the solvent.

[Study on chemical constituents from petroleum ether-soluble parts of cones of Platycladus orientalis].

OBJECTIVE: To study chemical constituents from petroleum ether-soluble parts of cones of Platycladus orientalis. METHODS: The compound were isolaeed by repeated column chromatography of silica gel and Sephadex LH-20. The structures were elucidated by physicochemical properties and spectrum analysis. RESULTS: Seven constituents were isolated and identified as sandaracopimaric acid (1), 6alpha-hydroxy sandaracopimaric acid (2), ent-isopimara-8 (14), 15-dien-3beta, 19-diol (3), ent-isopimara-8 (9), 15-dien-3beta-ol (4), ent-isopimara-8 (14),15- dien-3beta-ol (5), isocupressic acid (6) and 15-acetylisocupressic acid (7). CONCLUSION: Compounds 2 and 7 are isolated from this genus for the first time.

Synthesis and biological evaluation of hydroxylated 3-phenylcoumarins as antioxidants and antiproliferative agents.

Based on the observed biological activities of coumarins and resveratrol, we synthesized fourteen hydroxylated 3-phenylcoumarins (stilbene-coumarin hybrids) including six novel ortho-hydroxy-methoxy substituted derivatives, 1-14, by Perkin reaction. We characterized these compounds concerning their antioxidant activity against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced pBR322 DNA strand breakage, and their antiproliferative effects on human promyelocytic leukemia HL-60 and human lung adenocarcinoma epithelial A549 cells. Structure-activity relationship information suggests that the introduction of ortho-hydroxy-methoxy groups and ortho-dihydroxy groups on the aromatic A ring could efficiently improve antiproliferative activity. Interestingly, a new derivative, 6-methoxy-7-hydroxy-3-(4'-hydroxyphenyl)coumarin, 9, behaved as a poor antioxidant but appeared to be the most potent antiproliferative agent among the compounds examined, and this activity was mediated by deregulation in cell cycle and induction of apoptosis.

Antioxidant and antiproliferative activities of hydroxyl-substituted Schiff bases.

Eight hydroxyl-substituted Schiff bases with the different number and position of hydroxyl group on the two asymmetric aromatic rings (A and B rings) were prepared by the reaction between the corresponding aromatic aldehyde and aniline. Their antioxidant effects against the stable galvinoxyl radical (GO(.)) in ethyl acetate and methanol, and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced DNA strand breakage, and their antiproliferative effects on human hepatoma HepG2 cells, were investigated. Structure-activity relationship analysis demonstrates that o-dihydroxyl groups on the aromatic A ring and 4-hydroxyl group attached to the aromatic B ring contribute critically to the antioxidant and antiproliferative activities.

Antioxidant activity of alpha-pyridoin and its derivatives: possible mechanism.

alpha-Pyridoin (1, 1,2-di(2-pyridyl)-1,2-ethenediol) is a unique enediol antioxidant. To explore the detailed antioxidant mechanism of alpha-pyridoin, we synthesized alpha-pyridoin and its 5,5'- or 6,6'-bis-substituted derivatives (2-7) and compared their capacities to scavenge galvinoxyl radical (GO*) and protect human red blood cells (RBCs) from oxidative haemolysis. It was found that the compounds (5 and 6) with a methyl or methoxy group at the 5-position exhibit significantly higher GO*-scavenging and anti-haemolysis activities than other derivatives and vitamin C. Kinetic analysis of the GO*-scavenging reaction and the effect of added base on the reaction rate revealed that in ethyl acetate, the reaction occurs primarily by the direct hydrogen atom transfer (HAT mechanism). However, in ethanol that supports ionization, the kinetics of the process is mostly governed by sequential proton loss electron transfer (SPLET mechanism).

4,4'-Dihydroxy-trans-stilbene, a resveratrol analogue, exhibited enhanced antioxidant activity and cytotoxicity.

Resveratrol (3,5,4'-trans-trihydroxystibene) is a natural phytoalexin present in grapes and red wine, which possesses a variety of biological activities including antioxidant activity. In order to find more active antioxidant with resveratrol as the lead compound we synthesized 4,4'-dihydroxy-trans-stilbene (4,4'-DHS). The antioxidant activities of resveratrol and 4,4'-DHS were evaluated by the reaction kinetics with galvinoxyl radical or Cu(II) ions, and the inhibition effects against free-radical-induced peroxidation of human erythrocyte ghosts. It was found that 4,4'-DHS exhibits remarkably higher antioxidant activity than resveratrol. The oxidative products of resveratrol and 4,4'-DHS in the presence of Cu(II) in acetonitrile were identified as the dihydrofuran dimers by spectroscopic method, and the antioxidant mechanism for 4,4'-DHS was proposed. In addition, 4,4'-DHS exhibits remarkably higher cytotoxicity against human promyelocytic leukemia (HL-60) cells than resveratrol.

Structural characterization, antioxidant and antibacterial activities of two heteropolysaccharides purified from the bulbs of Lilium davidii var. unicolor Cotton.

Two heteropolysaccharides, BHP-1 and BHP-2, were separated and purified from the edible bulbs of Lilium davidii var. unicolor Cotton by anion-exchange and gel-permeation chromatography. The primary structural characteristics of BHP-1 and BHP-2 were investigated by Congo red test, X-ray diffractometry (XRD) analysis, IR, GC and NMR. The results showed that the weight-average molecular weight (MW) and number-average molecular weight (Mn) of BHP-1 and BHP-2 were nearly 1.93 × 105 g/moL, 8.86 × 104 g/moL and 3.52 × 104 g/moL, 2.95 × 104 g/moL, respectively. Glucose and mannose comprised BHP-1 in a relative molar ratio of 5.9:2.0, and BHP-2 was consisted of glucose, galactose, mannose and arabinose with approximate molar ratios of 8.3:1.5:1.0:1.1. Their backbone mainly contained α-(1 → 4)-linked d-glucopyranosyl. In addition, the C-6 of the glucose and C-2 of mannose residue of BHP-1 and BHP-2 were substituted. The two polysaccharides were semi-crystalline substance with multi-branching structure and triple helix conformation. Bioassays showed that BHP-1 and BHP-2 had effective antioxidant activities evaluated by DPPH, scavenging superoxide radical and OH radical in a dose-dependent manner. The two heteropolysaccharides also displayed distinct and selective antibacterial activity against B. cereus, P. putida, M. luteus and K. pneumonia with inhibition zones of 13 mm, 16 mm, 17 mm, 23 mm and 12 mm, 17 mm, 19 mm, 20 mm, respectively. These findings provided a reference for potential applications of the polysaccharides from L. davidii as natural antioxidants and antibacterial agents in food and pharmaceuticals.

Purification, characterization and antioxidant activities of a polysaccharide from the roots of Lilium davidii var. unicolor Cotton.

A polysaccharide (LPR) was separated from the roots of Lilium davidii var. unicolor Cotton with hot water extraction, ethanol precipitation, and purification by anion-exchange and gel-permeation chromatography. LPR was characterized. The weight-average molecular weight (MW) of LPR was 5.12 × 104 g/moL. Glucose and mannose comprised LPR with a molar ratio of 2.9:3.3. IR, NMR and methylation analysis showed that LPR was a natural O-acetyl glucomannan, the backbone mainly contained ß-(1 → 4)-linked d-glucopyranosyl and ß-(1 → 4)-linked D-mannopyanosyl, and the branches probably linked at O-2 and/or O-3 of the mannosyl and glucosyl residues. The acetyl groups mainly attached at O-2 or O-3 of mannosyl residues. X-ray diffractometric (XRD) analysis and scanning electron microscopy (SEM) analysis revealed that LPR was a semi-crystalline substance with porous lamellar structure. Bioassays in vitro indicated that LPR had distinct scavenging activities on hydroxyl radical and DPPH radical. These findings provided a reference for functional underutilization roots of L. davidii as natural antioxidant in food and pharmaceutical industry.

Bio-guided isolation of plant growth regulators from allelopathic plant-Codonopsis pilosula: phyto-selective activities and mechanisms.

Natural pesticides are the subject of growing interest, as the overuse of synthetic pesticides severely threatens the safety of humans and the eco-environment. Allelopathic plants can release plentiful secondary metabolites as natural plant growth regulators to affect the growth of neighboring plants. Bio-guided isolation of the aerial waste part of typical allelopathic plant-Codonopsis pilosula led to six active compounds being produced, including ginsenoside Rg1 (1), ginsenoside Re (2), luteolin (3), luteolin-5-O-glucoside (4), ginsenoside Rb1 (5) and lobetyolin (6). Ginsenosides and luteolin-5-O-glucoside were firstly found in Codonopsis. Phyto-activity tests showed that all compounds showed inhibiting effects toward C. pilosula, and compounds 2, 4, 5 and 6 were also inhibitors of Amaranthus retroflexus. By contrast, the compounds promoted the seedling growth of wheat, rice and Setaria viridis. At certain concentrations, compounds 1, 4, 5 and 1, 2, 4 could observably promote the growth of wheat and rice seedlings, respectively, exceeding Setaria viridis. The different effects toward the two weeds might be related to the different ROS levels induced by the compounds. The ROS amounts in the root tips of S. viridis were as low as those in the control test, and the ROS content in the root tips increased with aggravation of the inhibition effect. In summary, successful isolation of phyto-selective chemicals from allelopathic plants may provide a promising method for natural herbicide screening. The compounds isolated could potentially be applied as inhibitors of dicotyledon weeds and promoters of monocotyledon crops for weed management in agriculture.

Codonopilate A, a Triterpenyl Ester as Main Autotoxin in Cultivated Soil of Codonopsis pilosula (Franch.) Nannf.

Codonopilate A (1), a triterpenyl ester, was isolated from monocultivated soil of annual Codonopsis pilosula and identified as the main autotoxin. The yield ratio of codonopilate A in dried soil was calculated as 2.04 µg/g. Other two triterpenoids, taraxeryl acetate (2) and 24-methylenecycloartanol (3), were isolated and identified as well showing weaker autotoxity. This was the first time that the potential allelochemicals and autotoxins in the cultivated soil of Codonopsis pilosula were reported. Accumulation of reactive oxygen species (ROS) induced by the autotoxins in the root tips of Codonopsis pilosula was considered as an important factor for the phytotoxic effect. This work systematically investigates the allelopathic and autotoxic effect of Codonopsis pilosula, and the preliminary autotoxic action mode of the three autotoxins. These findings are helpful to understand the molecular mechanism of autotoxicity and conducive to explore proper ways to degrade the autotoxins and eliminate the replanting problems of Codonopsis pilosula.

Cycloartane-type triterpenoids from Astragalus hoantchy French.

A new cycloartane-type triterpenoid, 3ß-acetoxy-9ß,19-cyclolanost-24E-ene-1α,16ß-diol-27-O-ß-d-glucopyranoside (1), together with three known ones (2-4) were isolated from the aerial parts of Astragalus hoantchy. The structure of compound 1 was elucidated by detailed spectroscopic analyses including 1D and 2D NMR, HRESIMS, and IR experiments. All of the four compounds were isolated from A. hoantchy for the first time. The antifungal activities of compounds 1-4 against a phytopathogenic fungus (Alternaria solani) were evaluated with the result that compound 3 exhibited a moderate activity with an IC50 value of 284 µg/mL.