Mobility and recalcitrance of organo-chromium(III) complexes

Hexavalent chromium [Cr(VI)] is a major industrial pollutant. Bioremediation of Cr(VI) to Cr(III) is a viable clean-up approach. However, Cr(VI) bioreduction also produces soluble organo-Cr(III) complexes, and little is known about their behavior in the environment. When tested with soil columns, citrate-Cr(III) showed little sorption to soil; malate-Cr(III) had limited partitioning with soil; and histidine-Cr(III) exhibited significant interaction with soil. It appears that the mobility varies depending on the organic ligand. Further, Ralstonia eutropha JMP 134 and Pseudomonas aeruginosa pAO1 readily degraded malate, citrate, and histidine, but not the corresponding organo-Cr(III) complexes. The recalcitrance is not due to toxicity, but the complexes are likely to cause hindrance to enzymes, as malate dehydrogenase and amino acid oxidase could not use malate-Cr(III) and histidine-Cr(III), respectively. The data are in agreement with the reports of soluble organo-Cr(III) complexes in the environment.

Heterologous expression of a serine carboxypeptidase-like acyltransferase and characterization of the kinetic mechanism

In plant secondary metabolism, beta-acetal ester-dependent acyltransferases, such as the 1-O-sinapoyl-beta-glucose:l-malate sinapoyltransferase (SMT; EC 2.3.1.92), are homologous to serine carboxypeptidases. Mutant analyses and modeling of Arabidopsis SMT (AtSMT) have predicted amino acid residues involved in substrate recognition and catalysis, confirming the main functional elements conserved within the serine carboxypeptidase protein family. However, the functional shift from hydrolytic to acyltransferase activity and structure-function relationship of AtSMT remain obscure. To address these questions, a heterologous expression system for AtSMT has been developed that relies on Saccharomyces cerevisiae and an episomal leu2-d vector. Codon usage adaptation of AtSMT cDNA raised the produced SMT activity by a factor of approximately three. N-terminal fusion to the leader peptide from yeast proteinase A and transfer of this expression cassette to a high copy vector led to further increase in SMT expression by factors of 12 and 42, respectively. Finally, upscaling the biomass production by fermenter cultivation lead to another 90-fold increase, resulting in an overall 3900-fold activity compared to the AtSMT cDNA of plant origin. Detailed kinetic analyses of the recombinant protein indicated a random sequential bi-bi mechanism for the SMT-catalyzed transacylation, in contrast to a double displacement (ping-pong) mechanism, characteristic of serine carboxypeptidases.

Novel biodegradable poly(1,8-octanediol malate) for annulus fibrosus regeneration

A novel elastic scaffold that simulates the deformability of annulus fibrosus (AF) and has good biocompatibility was developed. The scaffold was formed of a malic acid-based polyester poly(1,8-octanediol malate) (POM), which was synthesized by direct polycondensation. The tensile strength of POM gradually increased with the extension of the polymerization time, while the degradation rate decreased. Rat AF cells proliferated on the POM films and maintained their phenotype. The 3D scaffold also supported the growth of the AF cells, as confirmed by Safranin-O and type II collagen staining. POM also demonstrated a good biocompatibility in an in vivo foreign body response assay, an important prerequisite for tissue engineering applications. This study suggests that elastic POM scaffold may be an ideal candidate for AF tissue engineering.

Synthesis and evaluation of water-soluble docetaxel prodrugs-docetaxel esters of malic acid

The synthesis of docetaxel esters of malic acid is described. These compounds were found to have greatly improved water solubility and are stable in solution at neutral pH. The C2' modified compounds 2a-c and 3a-c behave as prodrugs, that is, docetaxel is generated upon exposure to human plasma, whereas the C7 and C2',7,10- l modified derivatives do not. 2'-dl-Malyl docetaxel sodium salt demonstrated enhanced antitumor activity in vitro when compared to docetaxel and showed the inhibitory effect on tumor growth in vivo.

Brain tumor tandem targeting using a combination of monoclonal antibodies attached to biopoly(beta-L-malic acid)

Tumor-specific targeting using achievements of nanotechnology is a mainstay of increasing efficacy of anti-tumor drugs. To improve drug targeting we covalently conjugated for the first time two different monoclonal antibodies, an anti-mouse transferrin receptor antibody and a mouse autoimmune anti-nucleosome antibody 2C5, onto the drug delivery nanoplatform, poly(beta-L-malic acid). The active anti-tumor drug components attached to the same carrier molecule were antisense oligonucleotides to vascular protein laminin-8. The resulting drug, a new Polycefin variant, was administered intravenously into glioma-bearing xenogeneic animals. The drug delivery system was targeted across mouse endothelial system by the anti-mouse transferring receptor antibody and to the tumor cell surface by the anti-nucleosome antibody 2C5. The targeting efficacies of the Polycefin variants bearing either two antibodies or each single antibody were compared in vitro and in vivo. ELISA confirmed the co-existence of two antibodies on the same nanoplatform molecule and their functional activities. Fluorescence imaging analysis after 24 h of intravenous injection demonstrated significantly higher tumor accumulation of Polycefin variants with the tandem configuration of antibodies than with single antibodies. The results suggest improved efficacy for tandem configuration of antibodies than for single configurations carried by a drug delivery vehicle.

Characterization of the malate-aluminum(III) complex using 1H and 27Al NMR spectroscopy

Structural elucidation of a malate-aluminum(III) complex has been carried out using 1H and 27Al NMR spectroscopy. The 1H chemical shift perturbation clearly indicated the interaction between malate and Al(III) ion. The measurements of 27Al NMR and 1H-13C HSQC spectra demonstrated that the major form of a complex comprised two equivalent malate ions and two unequivalent Al(III) ions. With this constraint, an equilibrium geometry of the complex was proposed by a semi-empirical molecular orbital calculation.

Chelate-assisted phytoextraction of heavy metals in a soil contaminated with a pyritic sludge

The occurrence of many polluted areas as that affected by the accident of the Aznalcóllar pyrite mine has promoted phytoremediation as a technology able to reduce the risk of heavy metal contamination at low cost. White lupin plant has been considered a good candidate for phytoremediation. We studied the capacity of several complexing agents to improve the ability of white lupin for heavy metal phytoremediation in soils with multi-elemental pollution from acid pyritic sludge. Solution-soil interaction was studied and pot experiments with sludge-affected soil were carried out to this end. The interaction experiments indicated that EDTA and NTA were more efficient than malate and citrate in solubilizing metals (Fe, Mn, Cu, Zn, Cd), with minimum differences between EDTA and NTA. The pot trial showed that NTA was able to mobilize toxic elements from sludge-polluted soil and hence increasing their concentrations in plant (Mn, Cu, Zn, As, Cd). However, the NTA treatment promoted an increase of toxic elements concentrations, especially for As, Cd, Pb, in the lixiviates exceeding the maximum permissible levels, so a careful management of chelate is necessary.

Possible role of the polyuronic components in accumulation and mobilization of iron and phosphate at the soil--root interface

With the aim to investigate the role of the polyuronic components in the accumulation of iron and phosphate at the soil-root interface, the interactions of Ca-polygalacturonates (PGAs) with Fe(III) and P ions and of Fe(III)-Ca-polygalacturonates (Fe-PGAs) with P ions were studied at pH 4.7. The role of citric, malic and pyruvic acids in the mobilization of Fe(III) and P, in the presence and absence of Ca(II) 2.5mM, was also investigated. The sorption kinetics evidenced that P diffuses freely through the calcium polysaccharidic matrix whereas Fe(III) accumulates as an hydroxypolymer. The sorption kinetics of P by the Fe-PGA indicated that the amount of P sorbed increases with increasing its initial concentration up to a constant value equal to 0.98micromol/3.87micromolmg(-1) of Fe(III)-polymer trapped. The FT-IR spectra of the P-Fe-PGA systems, show bands attributable to P-O(H) stretching vibrations. The study of systems with a constant initial P amount and varying Fe(III) amounts allowed to hypothesize that phosphate settles down inside holes formed by the carboxylate groups of galacturonic units. Citric and malic acids showed to be active in the mobilization of both Fe and P whereas pyruvic acid appeared inactive.

Insights into the autotrophic CO2 fixation pathway of the archaeon Ignicoccus hospitalis: comprehensive analysis of the central carbon metabolism

Ignicoccus hospitalis is an autotrophic hyperthermophilic archaeon that serves as a host for another parasitic/symbiotic archaeon, Nanoarchaeum equitans. In this study, the biosynthetic pathways of I. hospitalis were investigated by in vitro enzymatic analyses, in vivo (13)C-labeling experiments, and genomic analyses. Our results suggest the operation of a so far unknown pathway of autotrophic CO(2) fixation that starts from acetyl-coenzyme A (CoA). The cyclic regeneration of acetyl-CoA, the primary CO(2) acceptor molecule, has not been clarified yet. In essence, acetyl-CoA is converted into pyruvate via reductive carboxylation by pyruvate-ferredoxin oxidoreductase. Pyruvate-water dikinase converts pyruvate into phosphoenolpyruvate (PEP), which is carboxylated to oxaloacetate by PEP carboxylase. An incomplete citric acid cycle is operating: citrate is synthesized from oxaloacetate and acetyl-CoA by a (re)-specific citrate synthase, whereas a 2-oxoglutarate-oxidizing enzyme is lacking. Further investigations revealed that several special biosynthetic pathways that have recently been described for various archaea are operating. Isoleucine is synthesized via the uncommon citramalate pathway and lysine via the alpha-aminoadipate pathway. Gluconeogenesis is achieved via a reverse Embden-Meyerhof pathway using a novel type of fructose 1,6-bisphosphate aldolase. Pentosephosphates are formed from hexosephosphates via the suggested ribulose-monophosphate pathway, whereby formaldehyde is released from C-1 of hexose. The organism may not contain any sugar-metabolizing pathway. This comprehensive analysis of the central carbon metabolism of I. hospitalis revealed further evidence for the unexpected and unexplored diversity of metabolic pathways within the (hyperthermophilic) archaea.

Examination of the Steps Leading up to the Physical Developer Process for Developing Fingerprints

This is a systematic study that examines several acid prewashes and water rinses on paper bearing latent prints before its treatment with a silver physical developer. Specimens or items processed with this method are usually pretreated with an acid wash to neutralize calcium carbonate from the paper before the treatment with a physical developer. Two different acids at varying concentrations were tested on fingerprints. Many different types of paper were examined in order to determine which acid prewash was the most beneficial. Various wash times as well as the addition of a water rinse step before the development were also examined. A pH study was included that monitored the acidity of the solution during the wash step. Scanning electron microscopy was used to verify surface calcium levels for the paper samples throughout the experiment. Malic acid at a concentration of 2.5% proved to be an ideal acid for most papers, providing good fingerprint development with minimal background development. Water rinses were deemed unnecessary before physical development.

Nanoconjugate based on polymalic acid for tumor targeting

A new prototype of polymer-derived drug delivery system, the nanoconjugate Polycefin, was tested for its ability to accumulate in tumors based on enhanced permeability and retention (EPR) effect and receptor mediated endocytosis. Polycefin was synthesized for targeted delivery of Morpholino antisense oligonucleotides into certain tumors. It consists of units that are covalently conjugated with poly(beta-l-malic acid) (M(w) 50,000, M(w)/M(n) 1.3) highly purified from cultures of myxomycete Physarum polycephalum. The units are active in endosomal uptake, disruption of endosomal membranes, oligonucleotide release in the cytoplasm, and protection against enzymatic degradation in the vascular system. The polymer is biodegradable, non-immunogenic and non-toxic. Polycefin was also coupled with AlexaFluor 680 C2-maleimide dye for in vivo detection. Nude mice received subcutaneous injections of MDA-MB 468 human breast cancer cells into the left posterior mid-dorsum or intracranial injections of human glioma cell line U87MG. Polycefin at concentration of 2.5mg/kg was injected via the tail vein. In vivo fluorescence tumor imaging was performed at different time points, 0-180 min up to 24h after the drug injection. The custom-made macro-illumination imaging MISTI system was used to examine the in vivo drug accumulation in animals bearing human breast and brain tumors. In breast tumors the fluorescence signal in large blood vessels and in the tumor increased rapidly until 60 min and remained in the tumor at a level 6 times higher than in non-tumor tissue (180 min) (p<0.003). In brain tumors drug accumulated selectively in 24h without any detectable signal in non-tumor areas. The results of live imaging were corroborated histologically by fluorescence microscopic examination of various organs. In addition to tumors, only kidney and liver showed some fluorescent signal.

A novel gene, screened by cDNA-AFLP approach, contributes to lowering the acidity of fruit in apple

cDNA-AFLP, coupled with bulked segregant analysis (BSA), was used to screen genes expressed differently between low- and high-acid apple fruits from hybrids of 'Toko' x 'Fuji' (Malus x domestica Borkh.). Sixty-four combinations of AFLP primers produced 2240 fragments, of which only one showed different expression between low- and high-acid fruits. The specific fragment was cloned and sequenced, and the complete cDNA was achieved by 3' and 5' rapid amplification of cDNA ends (RACE). The screened gene, designated as Mal-DDNA (GenBank accession no. DQ417661), showed no significant homology to clones in GenBank. The relatedness between fruit acidity and the transcription level of Mal-DDNA was identified by RT-PCR analysis on 30 hybrids. RT-PCR analysis indicated that Mal-DDNA transcripted in low-acid fruits at both early and ripe stages whereas in high- and mid-acid fruits, it did not transcript at the early stage. RNA gel-blot hybridization indicated that Mal-DDNA transcripted only in fruits and had clear difference between low- and high/mid-acid fruits. There was a good indication that Mal-DDNA existed as one copy in apple genome by Southern blot. Possible regulation of Mal-DDNA in apple fruit acidity is also discussed in the paper.

An Improved Method for the Extraction of Low Molecular Weight Organic Acids in Variable Charge Soils

Due to specific adsorption to variable charge soils, low molecular weight organic acids (LMWOAs) have not been sufficiently extracted, even if common extractants, such as water and 0.1 M sodium hydroxide (NaOH), were employed. In this work, the method for extracting LMWOAs in soils with 0.1 M NaOH was improved for variable charge soils; e.g. 1.0 M potassium fluoride (KF) with pH 4.0 was applied as an extractant jointed with 0.1 M NaOH based on its stronger ability to change the electrochemical properties of variable charge soils by specific adsorption. With the proposed method, the recoveries of oxalic, tartaric, malic, citric and fumaric acids were increased from 83 +/- 4, 93 +/- 1, 22 +/- 2, 63 +/- 5 and 84 +/- 3% to 98 +/- 2, 100 +/- 2, 85 +/- 2, 90 +/- 2 and 89 +/- 2%, respectively, compared with NaOH alone. Simultaneously, the LMWOAs in Agri-Udic Ferrosol with field moisture were measured with a satisfactory result.

Thermodynamics and kinetics of the glyoxylate cycle

Because the standard Gibbs energies of formation of all the species of reactants in the glyoxylate cycle are known at 298.15 K, it is possible to calculate the apparent equilibrium constants of the five reactions in the cycle in the pH range 5-9 and ionic strengths from 0 to approximately 0.35 M. In making calculations on such a system, it is convenient to specify concentrations of coenzymes like NADox and NADred because they are involved in many reactions and may be in steady states. Calculations are given for [NADox] = 1000[NADred] and [NADox] = 10[NADred]. Equilibrium compositions are calculated using computer programs when all the reactants are present initially and when only glyoxylate and CoA are present initially. The kinetics of the reactions in the glyoxylate cycle at specified concentrations of NADox and NADred are calculated by numerical solution of the steady-state rate equations for the case where the reactant concentrations are below their Michaelis constants and only glyoxylate and CoA are present initially.

Driving Parts of Krebs Cycle in Reverse through Mineral Photochemistry

Scenarios for driving the Krebs cycle in reverse in the absence of enzymatic networks have received much attention in the literature of prebiotic evolution because repeated cycling provides a core mechanism for the synthesis of useful biomolecules from carbon dioxide. Here, we show that three of the five reductive steps in the cycle can be driven photochemically at high yield by a ZnS colloid. The results show the conversion of oxaloacetate to malate, fumarate to succinate, and oxoglutarate to oxalosuccinate. The experimental conditions of circumneutral pH and 288 K, as well as the ZnS semiconductor photocatalyst particles (sphalerite), are believed to have been prevalent in the waters of early Earth. These findings therefore both establish and constrain the plausibility of the occurrence of heretofore difficult chemical conversions in prebiotic metabolic systems.

Thermal Decomposition of Fungal Poly(β,l-malic acid) and Poly(β,l-malate)s

The thermal decomposition of poly(beta,l-malic acid), poly(alpha-methyl beta,l-malate), and ionic complexes of the polyacid with alkyltrimethylammonium salts was studied by TGA, GPC, and FTIR and NMR spectroscopy. It was found that poly(beta,l-malic acid) depolymerized above 200 degrees C by an unzipping mechanism with generation of fumaric acid which is then partially converted in a mixture of maleic acid and anhydride. On the contrary, random scission of the main chain was found to happen in the thermal decomposition of poly(alpha-methyl beta,l-malate). On the other hand, ionic poly(beta,l-malate)s degraded through a well defined three-stage process, the first one being depolymerization of the poly(malate) main chain along with decomposition of the ionic complex. Decomposition of the previously generated alkyltrimethylammonium salts followed by unspecific cracking of the resulting nitrogenated compounds happened at higher temperatures. Mechanisms partially explaining the decomposition processes of the three studied systems were proposed according to collected data.

Some non-equilibrium phenomena in the malic acid/water/Polysorbate 81 system

Topical formulations undergo radical structural changes after application and the action on the skin is not directly related to the original structure of the formulation. This fact has been well established in the scientific literature. However, and more essential, is the fact that these changes in the formulation structure are not equilibrium ones. Especially so, with the hydroxy acids, which are widely used in cosmetic and dermatological treatment of skin. The article reports the first investigation into the non-equilibrium conditions in a hydroxy acid system. Different phases in the title system, which were not in mutual equilibrium, were brought in contact while avoiding convection. The transfer of substance between them was estimated from the changes in volume of each phase. The results showed, unexpectedly, that the systems were far from equilibrium even after prolonged times in contact. The kinetics of the changes varied to significant degree, from extremely slow, when solid phases were involved to fast for liquid phases. In one case was observed a separated layer, which was not found in the phase diagram under equilibrium conditions.

Cerium isotope effects in Ce(III) malate and lactate complex formation studied by long-distance displacement chromatography

Isotope effects of cerium were observed in malate and lactate complex formations during the long-distance displacement chromatographic processes at 313 K. Heavier isotopes were found fractionated in the frontal edges of the Ce adsorption bands in both the systems, registering a preference of the heavier isotopes for the Ce(III) complexes in the solution phase over the simply hydrated Ce(III) ions in the resin phase. The fractionation coefficients epsilon for the 136Ce/140Ce, 138Ce/140Ce and 142Ce/140Ce isotopic pairs were 7.1 x 10(-6), 5.2 x 10(-6) and -2.1 x 10(-6) for the malate system, and 4.8 x 10(-6), 4.5 x 10(-6) and-2.6 x 10(-6) for the lactate system, respectively. They all show the mass-dependent law if the deviation of epsilon for the 138Ce/140Ce pair was considered merely due to the isobaric interference in Ce isotopic ratio measurements, suggesting the molecular vibration, rather than the nuclear field shift, mainly contributes to the Ce isotope effects in the complex formation systems. The absolute values of epsilon between the two systems are comparable, suggesting no instinct difference in structural properties between Ce malate and lactate complexes involved.

[Effects of organic acids on Cd desorption of South China red soil]

Cadmium (Cd) pollution greatly threatens the environment of South China, where the economy developed very fast during last 20 years. In this paper, batch experiments were conducted to study the effects of three organic acids and their mixed solutions on the Cd desorption of red soil in this region. The results showed that oxalic acid and malic acid retarded the Cd desorption, but oxalic acid promoted it when the concentration was 20 mmol x L(-1) and soil pH value was higher than 5.0. With the increase of soil pH, Cd desorption decreased rapidly in the presence of oxalic acid and malic acid. Citric acid retarded Cd desorption at pH < 5.0, but promoted it at pH > 5.0. When the concentration of citric acid was 2 mmol x L(-1) and pH value changed from 3.0 to 7.0, Cd desorption declined first, increased then, and declined again. But, at the citric acid concentration of 20 mmol x L(-1), Cd desorption declined first till pH 4.0, and increased then till pH 7.0. At low pH (3.0 and 4.0), malic acid desorbed most Cd; while at high pH (5.0-7.0), citric acid desorbed most Cd. The Cd desorption rate was much higher in the presence of citric acid than oxalic acid and malic acid. Organic acids did not interactive effect on Cd desorption. The Cd desorption rate by mixed acids was within the range of that by single acid alone.

Determination of the biogenic amines in musts and wines before and after malolactic fermentation using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate as the derivatizing agent

An accurate, rapid and sensitive high-performance liquid chromatographic (HPLC) method is reported for the determination of four biogenic amines in red and white wine samples. The method involves derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) followed by liquid chromatography gradient elution analysis without any other sample pretreatment. The procedure developed permitted the determination of the four amines in 40 min. The relative standard deviation (RSD) values ranged from 3.1% to 6.1% in peak areas and the response was linear (R2>0.994) in a range from 0.1 to 4 mg/l. Leaving aside putrescine in Tempranillo wines, the malolactic fermentation did not exert any effect on the concentration of these compounds. On the contrary, the influence of the grape variety was important, and Tempranillo wines showed higher levels of tyramine and histamine and lesser of putrescine and cadaverine (p<0.05) than wines made with Cabernet Sauvignon.

Polycefin, a new prototype of a multifunctional nanoconjugate based on poly(beta-L-malic acid) for drug delivery

A new prototype of nanoconjugate, Polycefin, was synthesized for targeted delivery of antisense oligonucleotides and monoclonal antibodies to brain tumors. The macromolecular carrier contains: 1. biodegradable, nonimmunogenic, nontoxic beta-poly(L-malic acid) of microbial origin; 2. Morpholino antisense oligonucleotides targeting laminin alpha4 and beta1 chains of laminin-8, which is specifically overexpressed in glial brain tumors; 3. monoclonal anti-transferrin receptor antibody for specific tissue targeting; 4. oligonucleotide releasing disulfide units; 5. L-valine containing, pH-sensitive membrane disrupting unit(s), 6. protective poly(ethylene glycol); 7. a fluorescent dye (optional). Highly purified modules were conjugated directly with N-hydroxysuccinimidyl ester-activated beta-poly(L-malic acid) at pendant carboxyl groups or at thiol containing spacers via thioether and disulfide bonds. Products were chemically validated by physical, chemical, and functional tests. In vitro experiments using two human glioma cell lines U87MG and T98G demonstrated that Polycefin was delivered into the tumor cells by a receptor-mediated endocytosis mechanism and was able to inhibit the synthesis of laminin-8 alpha4 and beta1 chains at the same time. Inhibition of laminin-8 expression was in agreement with the designed endosomal membrane disruption and drug releasing activity. In vivo imaging showed the accumulation of intravenously injected Polycefin in brain tumor tissue via the antibody-targeted transferrin receptor-mediated endosomal pathway in addition to a less efficient mechanism known for high molecular mass biopolymers as enhanced permeability and retention effect. Polycefin was nontoxic to normal and tumor astrocytes in a wide range of concentrations, accumulated in brain tumor, and could be used for specific targeting of several biomarkers simultaneously.

A Simple, Short, and Flexible Synthesis of Viridiofungin Derivatives

Described herein is a simple, flexible, and efficient synthesis of the skeleton of the viridiofungins, a family of microbial secondary metabolites. The synthesis utilizes an asymmetric aldol reaction of a chiral oxazolidinone, a diastereoselective alkylation of a chiral 1,3-dioxolan-2-one, and a geometrically selective alkene cross-metathesis reaction as the key C-C bond-forming steps.

Bioactive constituents from Chinese natural medicines. XVII. constituents with radical scavenging effect and new glucosyloxybenzyl 2-isobutylmalates from Gymnadenia conopsea

The methanol-eluted fraction of the methanolic extract from the tubers of Gymnadenia conopsea was found to show radical scavenging activities for DPPH and super oxide anion (.O2-) radicals. Three new glucosyloxybenzyl 2-isobutylmalates, gymnosides VIII, IX, and X, were isolated from this natural medicine together with 58 known constituents. The stereostructures of gymnosides were elucidated on the basis of chemical and physicochemical evidence. In addition, the phenanthrene and dihydrostilbene constituents showed radical scavenging activities and suggested the following structural requirements on radical scavenging activities; a) phenanthrenes: 1) dihydrogenation at the 9,10-positions enhances the activities, 2) the 1 or 3-p-hydroxybenzyl group enhances the activities; b) dihydrostilbenes: 1) methylation of the 3'-position reduces the activities, 2) the 2- and/or 6-p-hydroxybenzyl groups enhance the activities.