Total syntheses and antimicrobial activities of pyridine alkaloids from Rubiaceae

Summary Pyridine alkaloids from Rubiaceae were prepared by palladium-catalyzed cross-coupling reactions of methyl 5-bromonicotinate (6) with various organometallic reagents. Baker's yeast reduction of the ketone8 gave the levorotatory alcohol (S)-1. On this basis, the naturally occurring alcohol (+)-1 was assigned to be (R)-configurated. The alkaloids1 and4 show weak antimicrobial activities.

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Totalsynthesen und antimikrobielle Aktivität von Pyridin-Alkaloiden aus Rubiaceen

Zusammenfassung Pyridin-Alkaloide aus Rubiaceen wurden durch palladium-katalysierte Kupplungsreaktionen von 5-Bromnicotinsäuremethylester (6) mit verschiedenen organometallischen Verbindungen hergestellt. Reduktion des Ketons8 mit Bäckerhefe ergab den linksdrehenden sekundären Alkohol (S)-1. Daher weist der natürlich vorkommende Alkohol (+)-1(R)-Konfiguration auf. Die Alkaloide1 und4 besitzen schwache antimikrobielle Aktivität.

     

Antimalarial and cytotoxic activities of pregnene-type steroidal alkaloids from Holarrhena pubescens roots

The phytochemical investigation of an alkaloidal extract of Holarrhena pubescens roots led to the isolation and identification of a new pregnene-type alkaloid, mokluangin D (1), together with nine known steroidal alkaloids (2–10). The structure of the new metabolite was determined on the basis of spectroscopic analyses including 1D- and 2D-NMR spectroscopy and mass spectrometry. Compounds 3 and 4 showed potent antimalarial activity against Plasmodium falciparum K1 stain with IC₅₀ values of 1.2 and 2.0 μM, respectively, and showed weak cytotoxic activity against the NCI-H187 cell line with IC₅₀ values of 27.7 and 30.6 μM, respectively. The substituent groups at C-3 and the carbonyl group at C-18 are important for the activity against the P. falciparum K1 stain.     

A review on analytical methods for natural berberine alkaloids

Berberine alkaloids, a group of protoberberine alkaloids under the classification of isoquinoline alkaloids, include berberine, coptisine, palmatine, columbamine, dehydrocorydaline, jatrorrhizine, and epiberberine from natural sources. Studies have shown that berberine alkaloids have various pharmacological functions, such as antibacterial, antiviral, blood pressure‐lowering, hypoglycaemic, antiarrhythmia, and anticancer effects. Therefore, it is worthwhile to develop analytical methods to investigate the pharmacokinetics and activity mechanisms of berberine alkaloids and to study berberine alkaloids more comprehensively. Current analytical methods for berberine alkaloids include liquid chromatography, thin‐layer chromatography, ultraviolet spectroscopy, capillary electrophoresis, and gas chromatography. The most widely used detection method is mass spectrometry. In order to provide a systematic and comprehensive summary and to serve as a reference for the future pharmacokinetics studies and analysis of berberine alkaloids, analytical methods for natural berberine alkaloids that have been used in the past ten years are reviewed here.     

New alkaloids from the leaves of Evodia rutaecarpa

One new indole alkaloid (1) and one new indole alkaloidal glycoside (2), together with nine known alkaloids (3–11), were isolated from the leaves of Evodia rutaecarpa. Their structures were determined on the basis of spectroscopic and chemical methods. Compound 4 exhibited potent activity against Pseudomonas aeruginosa with an MIC value of 7.13 μg/ml.     

Molecular design,synthesis and biological activities of amidines as new ketol-acid reductoisomerase inhibitors

Diamidine （A） was identified in our in vitro bio-assay as a possible inhibitor of ketol-acid reductoisomerase （KARI） from the ACD database search based on the known three-dimensional crystal structure of KARI. An investigation on interaction of A on KARI active sites, led to the design and synthesis of 15 novel monoamidines. Some of those showed better biological activity than A on rice KARI （in vitro） and in greenhouse herbicidal tests （in vivo）. The structure-biological activity relationship was investigated, which provides valuable information to further study of potential KARI inhibitors.     

Simultaneous determination of thirteen plant alkaloids in a human specimen by SPE and HPLC

A new screening method for the simultaneous determination of thirteen plant alkaloids (aconitine, anabasine, atropine, brucine, colchicine, cotinine, cytisine, harmine, ibogaine, nicotine, scopolamine, strychnine, yohimbine) in a human specimen was developed based on solid-phase extraction and reversed-phase liquid chromatography with photodiode array detection. The validated method enables selective identification as well as accurate and sensitive quantification. The analysis of forensic and clinical samples emphasizes the applicability for intoxications and drug abuse, as well as for compliance control.     

Enantiomer separation and preparation of five organophosphorus compounds and their biological activities

Summary The direct enantiomeric resolution of five O-aryl O-alkyl N-alkyl-phosphoramidothioates was carried out and their pure enantiomers were prepared on a commercially available Pirkle model chiral column (OA-4700). Absolute configurations of the enantiomers were determined by circular dichroism (CD) spectroscopy. S-enantiomers were the first compounds to elute chromatographically and the chromatographic elution order was in accordance with the results of computer simulating calculation. The biological activity test suggested that all the S-enantiomers were more active than R-enantiomers in killing barnyard grass.     

Current perspectives on quinazolines with potent biological activities: A review

Quinazoline is a heterocyclic compound having biological activities. It is aromatic in nature having bicyclic structure containing benzene ring and pyrimidine ring. Quinazoline and its derivatives are found to have wide range of biological activities that is anticancer, analgesic, antimicrobial, antihypertensive, anticonvulsant, antimalarial, antitumor, and anti-tubercular activities. The purpose of this review is to highlight the recent researches made by researchers on various biological activities of quinazoline derivatives on different targets.     

Updates on synthesis and biological activities of 1,3,4-oxadiazole: A review

The new era of heterocyclic moieties which are developed in the decades plays a very important role in the treatment of various diseases. Among them are 1,3,4-oxadiazoles, a heterocyclic five-membered ring which plays an vital role in the development of newer medicinal compounds for treating various biological activities, such as proliferation of cells, tuberculosis, allergy, viral diseases, etc. The present review will summarize the various synthetic approaches which will be correlated with the biological activities so that the information in future may be used by many researches to give a path breaking lead in the field of medicinal chemistry.     

Antiparasitic activity of certain isoquinoline alkaloids and their hypothetical complexes with oligonucleotides

The antiparasitic activity of two tetrahydrodiisoquinoline alkaloids 2, 3, β-allocryptopine (4), protopine (5), and a substituted phenylethylamine 6 was studied. Compounds 2 and 6 inhibited the growth of the parasite Leishmania donovani. The capability of the examined compounds to bind DNA was estimated by molecular modeling. It has been shown that binding occurs in the small groove and primarily at the AT-enriched part of the oligonucleotide. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 270–274, May–June, 2008.     

Synthesis and biological activities of some fluorine-and piperazine-containing 1,2,4-triazole thione derivatives

A series of fluorine-and piperazine-containing 1,2,4-triazole thione derivatives were synthesized by the Mannich reaction of triazole intermediates with various substituted piperazines and formaldehyde in high yields. Structures of title compounds were confirmed by melting points, IR, ¹H NMR, ¹³C NMR and elemental analysis. The preliminary bioassays for 17 novel title compounds showed that several compounds have significant fungicidal activity against Cercospora arachidicola, Physalospora piricola and Rhizoctonia cerealis at 50μg/mL.     

Current perspectives on benzoflavone analogues with potent biological activities: A review

Medicinal chemistry investigators have isolated and synthesized benzoflavone analogues with diverse bioactivities including enzyme inhibitory activity, central nervous system (CNS) activity, anti-inflammatory activity, anti-microorganism activity, hypoglycemic activity, and receptor modulating potential. SAR (Structure-Activity Relationship) studies have been conducted extensively and plenty of benzoflavone analogues have been prepared for potential targets. Herein, we review the pharmacology properties and SAR for benzoflavone analogues, and provide a brief summarization of synthetic strategies, wishing to give perspective on the research and development of benzoflavone derivatives.     

Lycopodium japonicum: A comprehensive review on its phytochemicals and biological activities

Lycopodium japonicum Thunb (Lycopodiaceae) is a common and abundant plant widely distributed in China, Japan and countries of Southern Asia and used in traditional Chinese medicine for the treatment of sprains, strains and myasthenia. This review focuses on the phytochemicals and biological actions, with the objective of stimulating further studies on the plant. 132 chemical compounds have been identified and isolated from this plant, and the most important are alkaloids and serratane triterpenoids. The isolated compounds of L. japonicum were shown to possess acetylcholinesterase inhibitory, cytotoxic, anti-inflammatory, anti-HIV-1 and α-glucosidase inhibitory activities. Further studies should be carried out on this plant in order to disclose many more active principles and mechanisms of active components.     

New pyrazinoquinazoline alkaloids Isolated from a culture of Stenotrophomonas maltophilia QB-77

Two new pyrazinoquinazoline alkaloids, epi-fiscalin D (1) and epi-fiscalin E (2), as well as three known analogues, norquinadoline A (3), quinadoline A (4), and fiscalin C (5), were isolated from ethyl acetate extract of the fermentation broth of Stentrophomonas maltophilia QB-77. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis including UV, HRESIMS, and 1D and 2D NMR experiments. All the isolated compounds were tested for their in vitro cytotoxicity against five human cancer cell lines (SMMC-7721, MCF-7, HL-60, SW480, and A-549) and antibacterial activities against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus.     

Flavonoids: biological activities and therapeutic potential

Abstract

Flavonoids have aroused much interest in research, since they present a great diversity of biological activities observed in vitro, such as: antioxidant effect, modulation of the enzymatic activity and inhibition of cellular proliferation, exerting beneficial effects on the organism, as well as the use of its therapeutic potential. With wide distribution in the plant kingdom represent a class of phenolic compounds that differ in their chemical structure and particular characteristics. The objective of this review was to describe the relevant aspects of flavonoids, reporting the different known groups, the probable mechanisms by which they act, their pharmacological properties and to gain a better understanding of the reported beneficial health effects of these substances. This systematic review consisted of research using scientific databases such as Scopus, Science Direct, PubMed, SciVerse and SciELO, without time limitation. Some pharmacological properties of some flavonoids and their health benefits have been confirmed by previous studies.     

Carbazole-pyranocoumarin conjugate and two carbazole alkaloids from the stems of Clausena excavata

A carbazole-pyranocoumarin conjugate, carbazomarin B (1), and two carbazole alkaloids, 6-methoxymukonidine (2) and 2-hydroxy-3-methoxycarbazole (3), together with 27 known compounds (4–30), were isolated from the stems of Clausena excavata. Their structures have been elucidated by spectroscopic analyses. Compound 2 showed moderate cytotoxicity to HuCCA-1, MOLT-3 and HepG2 cancer cell lines with IC₅₀ values of 15.09–28.50 μg/mL, but none to A549 cell line. Heptaphylline (6) and nordentatin (23) were found to show moderate cytotoxic activity against HepG2 cell line with IC₅₀ values of 12.33 and 11.33, respectively, while clausine K (27) exhibited strong cytotoxicity with IC₅₀ value of 1.05 μg/mL, better than a standard drug (etoposide, IC₅₀ 13.40 μg/mL).     

Toxicity and local anesthetic activity of diterpenoid alkaloids

The toxicity and local anesthetic activity of 74 diterpenoid alkaloids differing in the nature and position of functional groups in lycoctonine, heteratisine, napelline, hetisane, atisane, and denudatine skeletons and their synthetic derivatives were investigated. Compounds with local anesthetic activity and duration of action surpassing that of cocaine for surface anesthesia and that of novocaine and lidocaine for infiltration and trunk administration were identified. Structural factors affecting the toxicity and local anesthetic activity of the studied compounds were discussed. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 477–484, September–October, 2007.