Synthesis and Antimicrobial Activity Evaluation of Homodrimane Sesquiterpenoids with a Benzimidazole Unit

Herein we report a feasible study concerning the synthesis and the in vitro antimicrobial activity of some new homodrimane sesquiterpenoids with a benzimidazole unit. Based on some homodrimane carboxylic acids, on their acyl chlorides and intermediate monoamides, a series of seven N-homodrimenoyl-2-amino-1,3-benzimidazoles and 2-homodrimenyl-1,3-benzimidazoles was synthesized. The syntheses involved the decarboxylative cyclization and condensation of the said acids or acyl chlorides with o-phenylendiamine and 2-aminobenzimidazole, as well as the p-TsOH-mediated cyclodehydration of the said monoacylamides. The structures of the synthesized compounds have been fully confirmed, including by the X-ray diffraction. Their biological activities were evaluated on five species of fungi (Aspergillus niger, Fusarium solani, Penicillium chrysogenum, P. frequentans, and Alternaria alternata) and two strains of bacteria (Bacillus sp. and Pseudomonas aeruginosa). Compounds 7 and 20 showed higher antifungal (MIC = 0.064 and 0.05 μg/mL) and antibacterial (MIC = 0.05 and 0.032 μg/mL) activities compared to those of the standards: caspofungin (MIC = 0.32 μg/mL) and kanamycin (MIC = 2.0 μg/mL), and compounds 4, 10, 14, and 19 had moderate activities.

From (-)-sclareol to Norlabdane Heterocyclic Hybrid Compounds

This review relates to chemistry of the well-known biologically active natural labdane diterpenoid (-)-sclareol easily available from Clary sage (Salvia sclarea L.). It is mainly used in industry, especially for synthesis of fragrance compounds and natural analogs. The paper covers achievements on the synthesis, structure determination and biological activity of molecular hybrid compounds bearing hydrazide and thiosemicarbazone fragments or diazine, 1,2,4-triazole, carbazole, 1,3-thiazole, 1,3,4-oxadiazole, 1,3,4-thiadiazole units prepared based on it.

Synthesis of Homodrimane Sesquiterpenoids Bearing 1,3-Benzothiazole Unit and Their Antimicrobial Activity Evaluation

Based on some homodrimane carboxylic acids and their acyl chlorides, a series of fourteen 2-homodrimenyl-1,3-benzothiazoles, N-homodrimenoyl-2-amino-1,3-benzothiazoles, 4′-methyl-homodrimenoyl anilides and 4′-methyl-homodrimenthioyl anilides were synthesized and their biological activities were evaluated on five species of fungi (Aspergillus niger, Fusarium solani, Penicillium chrysogenum, P. frequentans, and Alternaria alternata) and two strains of bacteria (Bacillus sp. and Pseudomonas aeruginosa). The synthesis involved the decarboxylative cyclization, condensation and thionation of the said acids, anhydrides or their derivatives with 2-aminothiophenol, 2-aminobenzothiazole, p-toluidine and Lawesson’s reagent. As a result, together with the desired compounds, some unexpected products 8, 25, and 27 were obtained, and the structures and mechanisms for their formation have been proposed. Compounds 4, 9, and 25 showed higher antifungal and antibacterial activity compared to the standards caspofungin (MIC = 1.5 μg/mL) and kanamycin (MIC = 3.0 μg/mL), while compound 8 had comparable activities. In addition, compounds 6, 17, and 27 showed selective antifungal activity at MIC = 2.0, 0.25, and 1.0 μg/mL, respectively.

Chemical Composition of the Essential Oil and Antimicrobial Properties of Crude Extract From Tanacetum Corymbosum (L.) Shi. Bip

The GC-MS analysis of the essential oil from Tanacetum corymbosum revealed the presence of 38 compounds, including terpenes - germacrene D, (Z)-β-farnesene, g-elemene, β-caryophyllene, aliphatic - palmitic and linoleic fatty acids, fatty alcohol n-octadecanol, higher alkane n-heneicosane as the major constituents. The in vitro antimicrobial assessment of the ethanolic extract showed promising antibacterial/antifungal activities against five Gram-(+), Gram-(-) and phytopathogenic bacteria species and two fungi strains. The data obtained in this study may be useful both for researchers and for producers interested in new or less studied species of medicinal plants in healthcare and their biological activities.

(+)-Larixol and Larixyl Acetate: Syntheses, Phytochemical Studies and Biological Activity Assessments

(+)-Larixol is a well-known labdane-type diterpenoid widely used in organic synthesis. The present review covers the (+)-larixol based chemical transformations, the results of phytochemical analysis of new (+)-larixol containing species, as well as recent data on biological activity of (+)-larixol and practical applications where it is mentioned.

The Use of Some Non-conventional Methods in Chemistry of Bicyclohomofarnesenic Methyl Esters

The present paper reports the results of microwave irradiation assisted method for the preparation of bicyclohomofarnesenic methyl esters versus classical Stoll and Hinder method. Moreover, the chemical transformations of bicyclohomofarnesenic methyl esters via anodic electrooxidation and dye-sensitized photooxidation were performed. A new method for the preparation of methyl 7-oxo-13,14,15,16-tetranorlabd-6,8(8)-dien-12-oate and the mechanism of electrochemical products formation are presented. The structure of all synthesized compounds was fully confirmed by spectral methods.

Minor acetylated metabolites from Euphrasia rostkoviana

The phenylethanoids rostkovianoside, 6'-O-acetylcrassifolioside and the flavonoid rutin 3‴-acetate, were isolated from the methanolic extract of the aerial parts of Euphrasia rostkoviana Hayne. The structures of these previously undescribed compounds were elucidated by interpretation of spectroscopic data. The acetylation of rutin was also carried out and four ester derivatives were spectroscopically characterized. Finally, a chromatographic method was established to easily identify the acetylated position.

Research survey on iridoid and phenylethanoid glycosides among seven populations of Euphrasia rostkoviana Hayne from the Alps

The traditional use of extracts of Euphrasia rostkoviana to relieve ocular inflammation or infections is well documented and supported by clinical studies. Various classes of chemical compounds such as iridoids, phenylethanoids, flavonoids and hydroxycinnamic acids have been reported. The present work aims to assess the chemical diversity among seven populations of Euphrasia rostkoviana found in northern Italy. A meticulous separation of components led to the isolation and structural characterization of two previously unrecorded phenylethanoids methoxycrassifolioside and deoxycrassifolioside and one previously undescribed terpene glucoside (1E,6E)-8-hydroxy-3,7-dimethyl-octa-1,6-dienyl 1-O-β-D-glucopyranoside. We have also identified known phenylethanoids and iridoids that are reported in this genus for the first time. Finally, a targeted quantitative analysis for the standardization of herbal preparations revealed that iridoids occur in all populations whereas the presence and the levels of rutin and phenylethanoids are highly variable.

Structure and cytotoxic activity of sesquiterpene glycoside esters from Calendula officinalis L.: Studies on the conformation of viridiflorol

Topic applications of Calendula officinalis L. lipophilic extracts are used in phytotherapy to relieve skin inflammatory conditions whereas infusions are used as a remedy for gastric complaints. Such a different usage might be explained by some cytotoxicity of lipophilic extracts at gastric level but little is known about this. Therefore, we screened the CH2Cl2 extract from the flowers of C. officinalis by MTT and LDH assays in human epithelial gastric cells AGS. This bioassay-oriented approach led to the isolation of several sesquiterpene glycosides which were structurally characterized by spectroscopic measurements, chemical reactions and MM calculations. The conformational preferences of viridiflorol fucoside were established and a previously assigned stereochemistry was revised. The compounds 1a, 2a and 3f showed comparably high cytotoxicity in the MTT assays, whereas the effect on LDH release was lower. Our study provides new insights on the composition of C. officinalis extracts of medium polarity and identifies the main compounds that could be responsible for cytotoxic effects at gastric level.

Formal synthesis of ( - )-pereniporin B and ( - )-cinnamosmolide

The paper describes a new pathway for an efficient synthesis of natural and bioactive drimanic compounds ( - )-pereniporin B (1) and ( - )-cinnamosmolide (2) from ketodiol 7, an intermediate obtained before from accessible labdane diterpenoid (+)-larixol (3). The key step involves allylic bromination of acetate 8 with N-bromosuccinimide. The in vitro antimicrobial and antifungal activities of all compounds are also reported. Their structures were confirmed by both spectroscopic data and chemical transformations.

Synthesis of C6 and C7 Functionalized Drimanes from Larixol and Sclareol

The current communication represents an extended abstract of the presentation delivered on the joint Moldo-Italian seminar “New frontiers in natural product chemistry”, held in the Institute of Chemistry, Academy of Sciences of Moldova on 30 September. An overview of the synthetic methods oriented to the synthesis of C6 and C7 functionalized euryfurans is provided.