Salt effects on the growth, mineral nutrition, essential oil yield and composition of marjoram (Origanum majorana)

The aim of this work was to investigate the growth, mineral nutrition and essential oil composition of marjoram aerial part. Seedlings were cultivated for 20 days on nutrient solution, and then transferred to hydroponic solution with different NaCl concentrations (0, 50, 100, 150 mM). Plants were harvested after 17 days of treatment. Mineral nutrition and essential oil composition of shoots were determined. Results showed that growth, water content and development of the different organs of marjoram plant were affected just at the highest NaCl concentration (150 mM). Furthermore, salt did not seem to affect leaf area and root length but reduced the number of leaves. An increase in the total leaf surface and its thickness was observed at different NaCl concentrations. At 50 mM NaCl, sodium was primarily accumulated in roots but at 150 mM, it was strongly accumulated in leaves. However, Cl^? accumulation was lower at higher NaCl concentrations. Essential oil yield of marjoram shoots was 0.12% in the control and 0.10% at 50 mM but an important decrease was observed at 100 mM (0.05%). Thirty-three components were identified belonging to different chemical classes. In the control, the essential oil was found to be rich in trans-sabinene hydrate (47.67%), terpinen-4-ol (20.82%) and cis-sabinene hydrate (7.23%). The proportions of these main compounds were differently affected by salt.     

Ratios of cis- and trans-Sabinene Hydrate in Origanum majorana L. and Origanum microphyllum (Bentham) Vogel

(+)-cis-Sabinene hydrate and (+)-trans-sabinene hydrate are the main monoterpenes found in marjoram (Origanum majorana), but can also be found in other Origanum species as well, as in e.g. Melaleuca alternifolia. The synthesis of sabinene hydrate in marjoram (Origanum majorana) is performed by sabinene hydrate synthase. It is claimed, that both, (+)-cis- and (+)-trans-sabinene hydrate are produced by the same enzyme in an exact ratio of 10:1. To verify this in vitro result in vivo, we analysed single plants of 20 different genotypes of Origanum majorana and of three different populations of Origanum microphyllum and calculated the ratios of (+)-cis- to (+)-trans-sabinene hydrates. In Origanum majorana a constant ratio of 20:1 could be found, whereas in Origanum microphyllum the ratio did not prove to be constant.     

DPPH radical scavengers from dried leaves of oregano (Origanum vulgare)

1,1-Dipehnyl-2-picrylhydrazyl (DPPH) radical scavenging activities were found in the extract of dried leaves of oregano (Origanum vulgare). The water-soluble active ingredients were isolated, and their structures were determined to be 4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybenzyl protocatechuate and 4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybenzyl 4-O-methylprotocatechuate by (1)H-, (13)C-NMR, DEPT, HMQC, and HMBC spectral analyses, and by NOE experiments. The DPPH radical scavenging activities of these compounds were compared with those of rutin, quercetin and rosmarinic acid at a concentration of 2 x 10(-5) M. The scavenging activity of 4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybenzyl protocatechuate was almost the same as that of quercetin and rosmarinic acid, but that of 4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybennzyl 4-O-methylprotocatechuate was less than that of quercetin, rosmarinic acid and 4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybenzyl protocatechuate. The amount of 4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybenzyl protocatechuate was estimated to be 3.8 mg/1 g of dried leaves by an HPLC analysis.     

Inhibitory effect of ursolic acid purified from Origanum majorana L on the acetylcholinesterase

We screened 139 herbal spices in search of the acetylcholinesterase (AChE) inhibitor from natural resources. AChE inhibitors, which enhance cholinergic transmission by reducing the enzymatic degradation of acetylcholine, are the only source of compound currently approved for the treatment of Alzheimer's Disease (AD). Among these herbs, edible plants and spices, the ethanol extract from Origanum majorana L. showed the highest inhibitory effect on AChE in vitro. By sequential fractionation of Origanum majorana L. the active component was finally identified as ursolic acid (3 beta-Hydroxyurs-12-en-28-oic acid). The ursolic acid of Origanum majorana L. inhibited AChE activity in a dose-dependent and competitive/non-competitive type. The Ki value (representing the affinity of the enzyme and inhibitor) of Origanum majorana L. ursolic acid was 6 pM, and that of tacrine was 0.4 nM. The concentration required for 50% enzyme inhibition of the active component (IC50 value) was 7.5 nM, and that of tacrine was 1 nM. This study demonstrated that the ursolic acid of Origanum majorana L. appeared to be a potent AChE inhibitor in Alzheimer's Disease.     

Synthesis of alpha-mannosylated phenolics as alpha-glucosidase inhibitors

BF3OEt2-catalysed glycosidation of phenolic compounds 3 and 6 with the mannofuranosyl glycosyl donor 2 separately gave the corresponding alpha-mannofuranosyl derivatives 4 and 7 in good yield, and the latter on selective deacetonation (hydrolysis) with 2% aqueous HCl afforded 5 and 8 respectively. Compounds 4 and 7 inhibited rat intestinal alpha-glucosidase more effectively than a standard drug acarbose.     

Insecticidal activity of Origanum majorana L. essential oil as anti‐cholinergic agent

The present study was focused on exploring the presence of active compounds in Origanum majorana essential oil (OmEO), and its various knock‐down effects against the rice moth, Corcyra cephalonica. GC–MS analysis detected the existence of major compounds such as monoterpenes, cis‐β‐terpineol and terpinen‐4‐ol with the total proportion of 52.16%. Fumigant toxicity against adult and larvae was calculated with an LC₅₀ value of 11.31 and 49.83 μL/L air, respectively. The contact toxicity against adult, pupa, larvae and eggs was observed with LC₅₀ value 2.54, 0.95, 2.78, and 0.49 μL/L, respectively. Furthermore, the influential repellent behavior against adults has been observed. Acetylesterase (AChE) inhibition activity of OmEO was observed against adult and larvae of C. cephalonica with an IC₅₀ value of 35.89 and 118.54 μL/mL, respectively. Moreover, computational docking study revealed the binding affinity of Cis‐β‐terpineol and terpinen‐4‐ol towards the active binding sites of AChE. On the other hand, Fluorescence‐assisted cytometry and comet assay confirmed the cytotoxic and genotoxic effect of OmEO at various concentrations on C. cephalonica. Altogether, the results showed the knock‐down effect of OmEO against C. cephalonica, and it could be a potential biocontrol measure against the stored product pest.     

Phenylethyl cinnamides: a new series of alpha-glucosidase inhibitors from the leaves of Aegle marmelos

A series of phenylethyl cinnamides, which included new compounds named anhydromarmeline, aegelinosides A and B, were isolated from Aegle marmelos leaves as alpha-glucosidase inhibitors. The structures of new compounds were characterized by spectroscopic data and chemical degradation. Of compounds isolated, anhydroaegeline revealed the most potent inhibitory effect against alpha-glucosidase with IC(50) value of 35.8 microM. The present result also supports ethnopharmacological use of A. marmelos as a remedy for diabetes mellitus.     

Sulfonamide chalcone as a new class of alpha-glucosidase inhibitors

Chalcones 1-20, a new class of glycosidase inhibitors, were synthesized, and their glycosidase inhibitory activities were investigated. Non-aminochalcones 1-12 had no inhibitory activity, however, aminochalcones 13-20 had strong glycosidase (alpha-glucosidase, alpha-amylase, and beta-amylase) inhibitory activities. In particular, sulfonamide chalcones 17-20 had more potent alpha-glucosidase inhibitory activity than aminated chalcone 13-16. 4'-(p-Toluenesulfonamide)-3,4-dihydroxy chalcone 20 (IC(50)=0.4microM) was the best inhibitor against alpha-glucosidase, and these sulfonamide chalcones showed non-competitive inhibition.     

Synthesis and pharmacological activities of xanthone derivatives as alpha-glucosidase inhibitors

Considerable interest has been attracted in xanthone and its derivatives because of their large variety of pharmacological activities. In this project, a series of hydroxylxanthones and their acetoxy and alkoxy derivatives were synthesized and evaluated as alpha-glucosidase inhibitors, aimed at clarifying the structure-activity correlation. The results indicated that these xanthone derivatives were capable of inhibiting in vitro alpha-glucosidase with moderate to good activities. Among them, polyhydroxylxanthones exhibited the highest activities and thus may be exploitable as a lead compound for the development of potent alpha-glucosidase inhibitors.     

HPLC-DAD analysis of arbutin produced from hydroquinone in a biotransformation process in Origanum majorana L. shoot culture

The hydroquinone glucoside arbutin is a plant derived compound medically applied due to its uroantiseptic activity. It also has skin whitening properties and thus is widely used in dermatology and cosmetology. Origanum majorana L. (Lamiaceae) is known to produce arbutin, however the content of the compound in cultivated plants is very variable and low. Since plant cell and tissue cultures are capable to perform specific biotransformation reactions including glucosylation, this investigation targeted the formation of arbutin from hydroquinone in agitated O. majorana shoot cultures. For this purpose different doses of hydroquinone (96, 144, 192, 288 and 384 mg/L of medium) were added to the culture flasks in one, two or three portions. Arbutin was qualitatively and quantitatively determined in methanol extracts from dry biomass and lyophilized media using HPLC-DAD. Cells of O. majorana shoot cultures efficiently converted hydroquinone into arbutin. The product was accumulated in the biomass and was not observed (or in trace amounts) in the medium samples. Different doses as well as portioning of the precursor had a significant impact on the biotransformation process. Arbutin accumulation increased from 0.23 ± 0.03 mg/g DW up to 52.6 ± 4.8 mg/g DW in the biomass. The highest product content was observed after the addition of 192 mg/L hydroquinone in three portions. The highest efficiency of the biotransformation process, i.e. 67.5 ± 5.2% was calculated for a dose of 96 mg/L precursor divided into three portions. After further optimization of the biotransformation process, O. majorana shoot cultures could serve as a rich source of arbutin.     

Biaryls and heterobiaryls as alpha-glucosidase and protein tyrosine phosphatase inhibitors

Various 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles (1a-d) have been synthesized as precursor for the synthesis of 3,4-dihydro-1H-isothiochroman (2a) and benzocycloalkanes (2b-e). Highly functionalized 9-thiaphenanthrene (3b) and phenanthrene (3a) have also been obtained from the reaction of 1c with thiochroman-4-one and 1-tetralone separately. Similarly 4 has been obtained by the ring transformation of 1d by 4-trifluoromethylacetophenone. Most of the synthesized compounds were evaluated for alpha-glucosidase and protein tyrosine phosphatase inhibitory activities. Some of the compounds, 2a, 3a and b and 4 displayed better alpha-glucosidase inhibitory activity compared to standard drug acarbose.     

Acylated flavonol monorhamnosides, alpha-glucosidase inhibitors, from Machilus philippinensis

Bioassay-guided fractionation and isolation of the active constituents from the leaf extract of Machilusphilippinense Merr. yielded two active compounds, kaempferol-3-O-alpha-l-rhamnopyranoside 3',4'-di-E-p-coumaroic acid ester (1) and 3'-E,4'-Z-di-p-coumaroic acid ester (2) when tested against a Bacillus stearothermophilus, a alpha-glucosidase type IV. The IC(50) values of 1 and 2 were 6.10 and 1.00muM, respectively. Further application of the HPLC-SPE-NMR hyphenated technique in the on-line characterization of other active ingredients present in the CH(2)Cl(2) - soluble fraction led to identification of luteolin (3) and seven additional 3-O-(coumaroyl-rhamnopyranosyl)-flavonols (4-10). Their structures were determined mainly by (1)H NMR spectroscopic analyses. Among the compounds identified, compounds 2, 4, 5, and 7 were hitherto unknown natural products.     

Potent alpha-glucosidase inhibitors purified from the red alga Grateloupia elliptica

Diabetes mellitus is a most serious and chronic disease whose incidence rates are increasing with incidences of obesity and aging of the general population over the world. One therapeutic approach for decreasing postprandial hyperglycemia is to retard absorption of glucose by inhibition of α-glucosidase. Two bromophenols, 2,4,6-tribromophenol and 2,4-dibromophenol, were purified from the red alga Grateloupia elliptica. IC₅₀ values of 2,4,6-tribromophenol and 2,4-dibromophenol were 60.3 and 110.4 μM against Saccharomyces cerevisiae α-glucosidase, and 130.3 and 230.3 μM against Bacillus stearothermophilus α-glucosidase, respectively. In addition, both mildly inhibited rat-intestinal sucrase (IC₅₀ of 4.2 and 3.6 mM) and rat-intestinal maltase (IC₅₀ of 5.0 and 4.8 mM). Therefore, bromophenols of G. elliptica have potential as natural nutraceuticals to prevent diabetes mellitus because of their high α-glucosidase inhibitory activity.     

COX-2 inhibitors from the leaves of Pellacalyx saccardianus Scortech (Rhizophoraceae)

Phytochemicals and anti-inflammatory activity were investigated in the leaves of Pellacalyx saccardianus from the Rhizophoraceae family. The powdered leaves were extracted using methanol in a soxhlet extractor. Purification of the methanol extract yielded two new compounds, (3S)(6R)-3-(4′-hydroxybenzyl)-6-(6″-hydroxyphenethyl)-2,2-dimethyl-piperidin-4-one and 1,2-O-(1-methylethylidene)fucoside, together with six known compounds, β-amyrin palmitate, squalene, 24-ethylcholesta-5,22,25-trien-3β-ol, 5R-hydroxy-1,7-bis(5-hydroxyphenyl)heptan-3-one, 1,7-bis(4-hydroxyphenyl)hept-4-en-3-one and methyl-l-fucoside. An anti-inflammatory assay using COX-2 revealed that β-amyrin palmitate possessed the highest inhibitory effect (96.8%) at the lowest concentration (0.01 μM), which was higher than that of the positive controls, resveratrol (90.2%, 0.01 μM) and indomethacin (79.20%, 100 μM). This is the first report on the isolation of phytochemicals from the leaves of P. saccardianus and their anti-inflammatory activity.     

New 6-hydroxyflavonoids and their methyl ethers and glycosides from Neurolaena oaxacana

Six new and nine known flavonoids were obtained from Neurolaena oaxacana. The known flavonoids are 6-hydroxykaempferol 3,7-dimethyl ether, quercetagetin 3,7-dimethyl ether, quercetin 3-methyl ether, axillarin, nodifloretin, 6-hydroxyluteolin 7-glucoside, kaempferol 3-glucoside, quercetagetin 7-glucoside and patulitrin. The new compounds are 6-hydroxykaempferol 3-methyl ether, quercetagetin 3,7-dimethyl ether 6-galactoside, quercetagetin 3-methyl ether 7-glucoside, the 6- and 7-glucosides of 6-hydroxykaempferol 3-methyl ether and quercetagetin 3-methyl ether 7-sulfate.     

Two potent competitive inhibitors discriminating alpha-glucosidase family I from family II

The inhibition kinetics for isoacarbose (a pseudotetrasaccharide, IsoAca) and acarviosine-glucose (pseudotrisaccharide, AcvGlc), both of which are derivatives of acarbose, were investigated with various types of alpha-glucosidases obtained from microorganisms, plants, and insects. IsoAca and AcvGlc, competitive inhibitors, allowed classification of alpha-glucosidases into two groups. Enzymes of the first group were strongly inhibited by AcvGlc and weakly by IsoAca, in which the K(i) values of AcvGlc (0.35-3.0 microM) were 21- to 440-fold smaller than those of IsoAca. However, the second group of enzymes showed similar K(i) values, ranging from 1.6 to 8.0 microM for both compounds. This classification for alpha-glucosidases is in total agreement with that based on the similarity of their amino acid sequences (family I and family II). This indicated that the alpha-glucosidase families I and II could be clearly distinguished based on their inhibition kinetic data for IsoAca and AcvGlc. The two groups of alpha-glucosidases seemed to recognize distinctively the extra reducing-terminal glucose unit in IsoAca.     

A review of alpha-glucosidase inhibitors from plants as potential candidates for the treatment of type-2 diabetes

Diabetes mellitus is a multifactorial global health disorder that is rising at an alarming rate. Cardiovascular diseases, kidney damage and neuropathy are the main cause of high mortality rates among individuals with diabetes. One effective therapeutic approach for controlling hyperglycemia associated with type-2 diabetes is to target alpha-amylase and alpha-glucosidase, enzymes that catalyzes starch hydrolysis in the intestine. At present, approved inhibitors for these enzymes are restricted to acarbose, miglitol and voglibose. Although these inhibitors retard glucose absorption, undesirable gastrointestinal side effects impede their application. Therefore, research efforts continue to seek novel inhibitors with improved efficacy and minimal side effects. Natural products of plant origin have been a valuable source of therapeutic agents with lesser toxicity and side effects. The anti-diabetic potential through alpha-glucosidase inhibition of plant-derived molecules are summarized in this review. Eight molecules (Taxumariene F, Akebonoic acid, Morusin, Rhaponticin, Procyanidin A2, Alaternin, Mulberrofuran K and Psoralidin) were selected as promising drug candidates and their pharmacokinetic properties and toxicity were discussed where available.

     

alpha-Glucosidase inhibition of 6-hydroxyflavones. Part 3: Synthesis and evaluation of 2,3,4-trihydroxybenzoyl-containing flavonoid analogs and 6-aminoflavones as alpha-glucosidase inhibitors

The SAR studies suggested that the C-ring of baicalein (1) was not necessary for the activity, and validated the importance of 2,3,4-trihydroxybenzoyl structure of 1. Thus, a series of 2,3,4-trihydroxybenzoyl-containing flavonoid analogs were investigated for the alpha-glucosidase inhibitory activity. The results indicated that 5,6,7-trihydroxy-2-phenyl-4-quinolone (2) and 5,6,7-trihydroxyflavanone (4) showed the comparable activity to 1, while 3,5,6,7-tetrahydroxyflavone (7), 5,6,7-trihydroxyisoflavone (8), and 6-hydroxygenistein (9) showed moderate alpha-glucosidase inhibitory activity. In addition, it was found that 6-amino-5,7-dihydroxyflavone (16) was a more potent and specific rat intestinal alpha-glucosidase inhibitor than 1, and showed the comparable activity to acarbose. This is the first report on mammalian intestinal alpha-glucosidase inhibitory activity of 6-aminoflavones. Kinetic studies revealed that 16 inhibited both sucrose- and maltose-hydrolyzing activities of rat intestinal alpha-glucosidase uncompetitively.     

2-(2-Chloro-6-fluorophenyl)acetamides as potent thrombin inhibitors

2-(2-Chloro-6-fluorophenyl)acetamides having 2,2-difluoro-2-aryl/heteroaryl-ethylamine P3 and oxyguanidine P1 substituents are potent thrombin inhibitors (K(i)=0.9-33.9 nM). 2-(5-Chloro-pyridin-2-yl)-2,2-difluoroethylamine was the best P3 substituent, yielding the most potent inhibitor (K(i)=0.7 nM). Replacing the P3 heteroaryl group with a phenyl ring or replacing the difluoro substitution with dimethyl or cyclopropyl groups in the linker reduced the affinity for thrombin significantly. The aminopyridine P1s also provided an increase in potency.     

Synthesis of 6(α,β)-aminocholestanols as ergosterol biosynthesis inhibitors

Δ⁷-5-Desaturase catalyses one of the last steps in ergosterol biosynthesis in fungi. Moreover Δ⁵-unsaturation is necessary for the sparking function. Synthesis of three pairs of C-6 epimeric cholestanol derivatives are described as potential growth inhibitors. Preliminary results suggest that 6β-aminocholestanol is a potent antifungal agent.