Characterization of essential oil from Ocimum gratissimum leaves: Antibacterial and mode of action against selected gastroenteritis pathogens.

Essential oil of fresh leaves of Ocimum gratissimum (OGEO) was water-steam distilled and analyzed by GC-MS. Thirty-seven compounds were identified, with eugenol (55.6%) as the major component followed by cis-ocimene (13.9%), γ-muurolene (11.6%), (Z,E)-α-farnesene (5.6%), α-trans-bergamotene (4.1%), and ß-caryophyllene (2.7%). Antimicrobial activity of OGEO was tested against four gastroenteritis pathogens (Staphylococcus aureus, Escherichia coli, Salmonella Typhimurium, and Shigella flexneri). OGEO exhibited antibacterial effect, with MICs of 1-2 mg ml-1, against the tested species. OGEO also displayed rapid killing effect within 5 s at four times of MIC against both E. coli and S. Typhimurium. Various assays were performed to investigate the mode of action of the oil. OGEO increased the permeability of microbial cell membrane as evidenced by LIVE/DEAD BacLight assay. Analyses of the release of absorbing materials at 260 nm, protein leakage, SDS-PAGE, and SEM strongly suggested the disruptive action of the oil on the cytoplasmic membrane of the tested microorganisms. Results revealed that the antibacterial property of OGEO could be due to membrane disruption.

Synthesis of 3-aminocoumarin-N-benzylpyridinium conjugates with nanomolar inhibitory activity against acetylcholinesterase.

A series of 3-amino-6,7-dimethoxycoumarins conjugated with the N-benzylpyridinium moiety through an amide-bond linkage was synthesized and evaluated for their acetylcholinesterase inhibitory activity. A number of the benzylpyridinium derivatives exhibited potent activities with inhibitory concentration (IC50) values in the nanomolar concentration range. Among them, the 2,3-difluorobenzylpyridinium-containing compound was the most potent inhibitor with an IC50 value of 1.53 ± 0.01 nM. Docking studies revealed that the synthesized compounds inhibit the target enzyme by a dual binding site mechanism whereby the coumarin portion binds with the peripheral anionic site while the N-benzylpyridinium residue binds with the catalytic anionic site of the enzyme.

Synthesis and anti-acetylcholinesterase activity of scopoletin derivatives.

A series of scopoletin derivatives incorporated with the pyridinium moiety was synthesized and evaluated for their acetylcholinesterase (AChE) inhibitory activity by the colorimetric Ellman's method. A 2-fluorobenzylpyridinium derivative was the most potent among the tested compounds, with an IC50 value of 0.215±0.015µM, which was greatly improved from that of scopoletin. Docking studies revealed that the scopoletin portion of the mentioned compound was bound to the peripheral anionic site of the AChE, whereas the N-benzylpyridinium residue to the catalytic anionic site.

Synthesis, Antiacetylcholinesterase Activity, and Molecular Dynamics Simulation of Aporphine-benzylpyridinium Conjugates.

A series of aporphines conjugated with an N-benzylpyridinium moiety through an amide-bond linkage were synthesized and evaluated for their acetylcholinesterase (AChE) inhibitory activity. The conjugation of the N-benzylpyridinium group significantly enhanced the AChE inhibitory activity of the core aporphine. The halogen substituents on the benzyl group affected the activity of the conjugates. Both (S)- and (R)-enantiomers of three conjugates with low IC50 values were synthesized and evaluated for their activities. All (S)-enantiomers exhibited higher activity than the corresponding (R)-enantiomers. The (S)-enantiomer of 2-chlorobenzylpyridinium-containing aporphine was the most potent inhibitor in this study with an IC50 value of 0.06 ± 0.003 µM. Molecular dynamics simulation analysis revealed that both enantiomers can interact with the AChE binding site, whereas the (S)-enantiomer possessed slightly stronger interaction than the (R)-enantiomer, presumably because of their different orientations, as evidenced by molecular docking. The N-benzylpyridinium dehydroaporphine conjugates were also synthesized but were less active than the corresponding aporphine conjugates.

Cholinesterase Inhibitory Activity and Molecular Docking Studies of Isocryptolepine-Triazole Adducts.

Due to the rising prevalence of Alzheimer's disease (AD), there is a pressing need for more effective drugs to treat or manage AD's symptoms. Studies have shown that cholinesterase inhibition can improve cognitive and behavioral symptoms associated with AD, by addressing the cholinergic deficit. Based on the recent development of cholinesterase inhibitors with indoloquinoline and triazole moiety, we rationalized that compounds with an isocryptolepine-triazole scaffold may also have the same biological targets. In this study, eighteen previously synthesized isocryptolepine-triazole compounds were assessed for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholine esterase (BChE). The majority of these compounds demonstrated potent selective AChE inhibition. Furthermore, our molecular docking and molecular dynamic simulation studies reveal that the isocryptolepine and triazole moieties are important for the binding of the compounds with the periphery of the AChE's binding pocket. While reductions in molecular weights and lipophilicities may be necessary to improve their pharmacokinetic properties, this work provides valuable insights for designing future AChE inhibitors, based on the novel isocryptolepine-triazole scaffold.

Synthesis of integerrimide A by an on-resin tandem Fmoc-deprotection-macrocyclisation approach.

A solid-phase total synthesis of integerrimide A (1) is reported. This work employs a safety-catch linker which enables head-to-tail cyclisation of the required linear peptide 6 as a method of cleaving the peptide from the solid support, and highlights a new tandem approach to direct macrocyclisation. It provides access to useful quantities of 1 in 16 steps and 19% overall yield, based on the manufacturer's stated resin substitution from commercially available materials, and also verifies the absolute stereochemistry of the natural product.

Cytotoxic and antimicrobial activities of aporphine alkaloids isolated from Stephania venosa (Blume) Spreng.

The cytotoxic activity of five alkaloids, namely 4,5-dioxo-dehydrocrebanine (1), dehydrocrebanine (2), crebanine (3), oxostephanine (4), and thailandine (5) isolated from the tuber and leaves of Stephania venosa (Blume) Spreng was investigated. Thailandine showed the strongest activity against lung carcinoma cells (A549) (IC50 of 0.30 µg/mL) with very low cytotoxicity against normal embryonic lung cells (MRC-5). Thailandine also demonstrated strong activity against Plasmodium falciparum, K1 strain (IC50 of 20 ng/mL), and Mycobacterium tuberculosis H(37)Ra (MIC of 6.25 µg/mL) as well as gram-positive bacteria such as Streptococcus pneumoniae and Staphylococcus aureus. Oxostephanine exhibited strong activity against breast cancer (BC) and acute lymphoblastic leukemia cells (MOLT-3) with an IC50 of 0.24 and 0.71 µg/mL, respectively, and exhibited very low cytotoxicity against MRC-5 cells. Dehydrocrebanine demonstrated strong activity against promyelocytic leukemia cells (HL-60) with an IC50 of 2.14 µg/mL whereas crebanine showed weak activity against cancer cell lines. However, both of them showed cytotoxicity against MRC-5 cells.

(-)-crebanine.

THE ASYMMETRIC UNIT OF THE TITLE COMPOUND [SYSTEMATIC NAME: 9,10-dimeth-oxy-7-methyl-6,7,7a,8-tetra-hydro-5H-benzo[g][1,3]benzodioxolo[6,5,4-de]quinoline], C(20)H(21)NO(4), contains two independent mol-ecules with very similar bond lengths and angles. The crystal packing exhibits voids of 131 Å(3).

Dipyridodiazepinone derivatives; synthesis and anti HIV-1 activity.

Ten dipyridodiazepinone derivatives were synthesized and evaluated for their anti HIV-1 reverse transcriptase activity against wild-type and mutant type enzymes, K103N and Y181C. Two of them were found to be promising inhibitors for HIV-1 RT.

Novel 2-chloro-8-arylthiomethyldipyridodiazepinone derivatives with activity against HIV-1 reverse transcriptase.

Based on the molecular modeling analysis against Y181C HIV-1 RT, dipyridodiazepinone derivatives containing an unsubstituted lactam nitrogen and 2-chloro-8-arylthiomethyl were synthesized via an efficient route. Some of them were evaluated for their antiviral activity against HIV-1 RT subtype E and were found to exhibit virustatic activity comparable to some clinically used therapeutic agents.

Roscotanes and roscoranes: Oxygenated abietane and pimarane diterpenoids from Kaempferia roscoeana.

Eight previously undescribed ditepenoids, including four oxygenated abietanes (roscotanes A-D) and four oxygenated pimaranes (roscoranes A-D), along with twelve known diterpenoids were isolated from the whole plants of Kaempferia roscoeana. Their structures were elucidated by extensive spectroscopic analysis, and the structure of roscotane A was further confirmed by single crystal X-ray diffraction analysis. Most isolated compounds were evaluated for their antimicrobial and antimalarial activities.

C-25 epimeric 26-haloponasterone A: synthesis, absolute configuration and moulting activity.

A convenient synthesis of inokosterone has been accomplished. Inokosterone exists as two C-25 epimers, which could be separated from each other through their diacetonide derivatives. The absolute configuration of these compounds was determined. Two C-25 epimers of 26-chloroponasterone A were synthesized from the respective C-25 epimeric inokosterone. Two epimeric 26-bromo and 26-iodoponasterone A compounds were also synthesized. Moulting activity of these compounds was evaluated using the Musca bioassay, and it was found that the (25S)-26-halo analogues were more active than the corresponding (25R)-26-halo analogues. Among the 25S series, an increase in activity with an increase in size of the halogen atom was observed, indicating that the steric factor was more important than the electronic factor in binding of these ecdysteroid analogues to the receptor. On the other hand, a decrease in activity with an increase in size of the halogen atom was noted in the 25R series, suggesting that the steric factor was less important than the electronic factor. The results indicated that the configuration at C-25 and the substituent at C-26 have significant influences on the interaction of ecdysteroids with their receptor.

Chemical modifications at the 22-hydroxyl group of ecdysteroids: alternative structural requirements for high moulting activity.

A number of 22-O-alkyl ether and acyl ester derivatives have been prepared and their moulting activity determined, using the Musca assay. It was found that a free 22-hydroxyl group is not an essential structural requirement for an ecdysteroid to exhibit high moulting activity. The activity of a 22-O-substituted ecdysteroid may even be higher than that of the parent compound, providing that the substituent constitutes a functional group that can enhance biological activity. The moulting activity is not sensitive to steric factors at the 22-position. Ecdysteroid without a 22-hydroxyl group may exhibit high moulting activity if a functional group that can enhance activity is present at an appropriate position.

Antimicrobial activity of coronarin D and its synergistic potential with antibiotics.

Coronarin D is a labdane-type diterpene from the rhizomes of Hedychium coronarium. In the view of our ongoing effort to explore its novel biological activity, antimicrobial activity study of coronarin D was performed. The results showed that coronarin D was active against tested Gram-positive bacteria, inactive for tested Gram-negative bacteria, and weakly active against tested fungi. The antibacterial effect of the combination of coronarin D with nine classical antibiotics against four Gram-positive bacteria was also evaluated. The fractional inhibitory concentration indices (FICI) of coronarin D-antibiotics combinations, calculated from the checkerboard assay, were used as synergism indicator. Out of 36 combinations, 47% showed total synergism, 33% had partial synergistic interaction, 17% showed no effect, and 3% showed antagonism. By combination with coronarin D at concentration of 0.25 minimal inhibitory concentration (MIC), the activities of antibiotics were boosted to 4- to 128-fold. These finding suggested an attractive approach to combat the infectious diseases by using coronarin D-antibiotic drug combination.

Antifungal activity of coronarin D against Candida albicans.

OBJECTIVE: The objective of this study was to investigate the antifungal activity of coronarin D on Candida albicans and its activity was compared with clotrimazole and nystatin. METHODS: Coronarin D was extracted by liquid chromatography and used in antifungal testing. The inhibitory effect of coronarin D on C. albicans was determined by cultures and an applied broth dilution test. The rate of fungicidal activity was evaluated by time-kill curves. Morphologic alterations of fungal cells were investigated using scanning electron microscopy. RESULTS: Coronarin D was effective against C. albicans; the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) were 2 and 4 mg/mL, respectively. The C. albicans killing activity of coronarin D was higher than clotrimazole and nystatin at 2 × MFC and 4 × MFC, respectively. Morphologic alterations of fungal cells consistent with cell membrane damage were observed in the coronarin D-treated cells. CONCLUSIONS: Coronarin D showed promising antifungal activity against C. albicans in vitro.

Prenylated flavonoids from the leaves of Derris malaccensis and their cytotoxicity.

A new prenylated isoflavone, pomiferin-4'-O-methyl ether, and a new prenylated chalcone, 2',4'-dihydroxy-4-methoxy-3'-(2-hydroxy-3-methylbut-3-enyl)chalcone, together with four known flavonoids, were isolated from the leaves of Derris malaccensis. All isolated compounds were evaluated for their cytotoxicity.

Labdane diterpenes from the rhizomes of Hedychium coronarium.

A new labdane diterpenoid, (E)-labda-8(17),12-dien-15,16-olide (1) together with eight known compounds, coronarin D (2), coronarin D methyl ether (3), coronarin D ethyl ether (4), isocoronarin D (5), coronarin B (6), labda-8(17),11,13-trien-15,16-olide (7), (E)-labda-8(17),12-diene-15,16-dial (8) and 16-hydroxylabda-8(17),11,13-trien-15,16-olide (9), are isolated from the rhizomes of Hedychium coronarium. Compounds 2-4, 5 and 9 are isolated as mixtures of C-15, C-14 and C-16 epimers, respectively. Their structures are determined on the basis of their spectroscopic data. The epimeric mixtures of 2 and 3 have not been reported before. Some of them were evaluated for their cytotoxicity.

Cytotoxic prenylated xanthones from the young fruit of Garcinia mangostana.

Three new prenylated xanthones, mangostenones C (1), D (2), and E (3), together with 16 known xanthones 4-19, were isolated from the young fruit (7-week maturity stage) of Garcinia mangostana. The structural elucidation of the new compounds was mainly established on the basis of 1D and 2D NMR and HR-MS spectroscopic analysis. Compound 1 showed cytotoxic properties against three human cancer cell lines, epidermoid carcinoma of the mouth (KB), breast cancer (BC-1), and small cell lung cancer (NCI-H187), with IC50 values of 2.8, 3.53, and 3.72 microg/ml, respectively. Among the isolates, alpha-mangostin (12), the major metabolite, exhibited the most potent effects against the BC-1 cells with an IC50 value of 0.92 microg/ml, an activity greater than that of the standard drug ellipticine (IC50 = 1.46 microg/ml). Compound 12 also showed the highest activity against KB cells, while gartanin (10) displayed the strongest activity against the NCI-H187 cells at the respective IC50 values of 2.08 microg/ml and 1.08 microg/ml.

Constituents of the leaves of Macaranga tanarius.

From the leaves of Macaranga tanarius, three new constituents, tanarifuranonol (1), tanariflavanone C (2), and tanariflavanone D (3), together with seven known compounds, were isolated and identified. Substances obtained in this investigation were evaluated against a panel of bioassays.

Proteomic profiling of cholangiocarcinoma cell line treated with pomiferin from Derris malaccensis.

Pomiferin, a prenylated isoflavonoid from Derris malaccensis with strong anti-fungal and anti-oxidant activities, showed cytotoxic activity towards human cholangiocarcinoma cells (HuCCA-1), with IC(50) of 0.9 microg/mL. Pomiferin caused apoptosis, detectable by DNA fragmentation. Two-dimensional PAGE showed increased expression of 12 proteins, namely glucose-regulated protein 75 (grp 75), calcyclin (S100A6), degraded cytokeratin 19, ATP synthase D, ribosomal protein P0, degraded cytokeratin 18 (two spots pI/MW 6.03/29.9 and pI/MW 4.66/21.5), cofilin, annexin A1, triose phosphate isomerase, peroxiredoxin-1, calgizzarin, and profilin. In contrast, cytokeratins (CK) 7, 18 and 19 were down-regulated, and were shown by 1-DE immunodetection to be degraded.