Synthesis of variously oxidized abietane diterpenes and their antibacterial activities against MRSA and VRE

A new diterpenoid from Salvia santolinifolia boiss

Phytochemical study of the Salvia santolinifolia root extract resulted in the isolation of one new quinone diterpenoid, aegyptinone E (1) as well as two known ones, aegyptinone A (2) and aegyptinone D (3). All the isolated compounds were reported for the first time from S. santolinifolia. Spectroscopic analyses including 1 D and 2 D NMR and HRESIMS were used to determine the chemical structures. Aegyptinone A (2) showed moderate antibacterial activity against Staphylococcus aureus, Staphylococcus epidermis, and Bacillus subtilis with MIC of 25 μg/mL.

Taxodin A, a Cytotoxic C30 Terpenoid from Taxodium mucronatum with a Unique Skeleton

Taxodin A (1), a unique C30 terpenoid featuring an unprecedented skeleton composed of an abietane-type diterpene and a menthane-type monoterpene, was obtained from the leaves and branches of Taxodium mucronatum. The structure and absolute configuration of compound 1 was unequivocally established by the combination of extensive spectroscopic analyses and X-ray single-crystal diffraction analysis. Compound 1 exhibited potent cytotoxic activities against A549, SMMC-7721, MDA-MB-231, and SW480 cell lines with IC50 values of 15.35±0.73, 8.49±0.35, 17.53±0.79, 18.93±0.60 μM, respectively.

Discovery and Bioinspired Synthesis of Salpratone A

Salpratone A (1), a novel abietane diterpenoid containing a unique cis-fused A/B ring, was isolated from Salvia prattii. Bioactivity studies showed that 1 has potent activity in inhibiting platelet aggregation induced by multiple agonists as well as antithrombotic efficacy in the FeCl3-induced rat in vivo thrombosis model. Furthermore, a bioinspired synthesis of 1 from the abundant natural product ferruginol was achieved in 6 steps with a 22% overall yield. The key steps include a stereoselective allyl oxidation and a subsequent regioselective Meinwald rearrangement.

Unified short syntheses of oxygenated tricyclic aromatic diterpenes by radical cyclization with a photoredox catalyst

The biomimetic two-phase strategy employing polyene cyclization and subsequent oxidation/substitution is an effective approach for divergent syntheses of [6-6-6]-tricyclic diterpenes. However, this strategy requires lengthy sequences for syntheses of oxygenated tricyclic aromatic abietane/podocarpane diterpenes owing to the many linear oxidation/substitution steps after cyclization. Here, we present a new synthetic route based on a convergent reverse two-phase strategy employing a reverse radical cyclization approach, which enabled the unified short syntheses of four aromatic abietane/podocarpane diterpenes and the divergent short syntheses of other related diterpenes. Oxygenated and substituted precursors for cyclization were convergently prepared through Friedel-Crafts acylation and rhodium-catalyzed site-selective iodination. Radical redox cyclization using an iridium photoredox catalyst involving neophyl rearrangement furnished the thermodynamically favored 6-membered ring preferentially. (±)-5,6-Dehydrosugiol, salvinolone, crossogumerin A, and Δ5-nimbidiol were synthesized in only 8 steps. An oxygenated cyclized intermediate was also useful for divergent derivatization to sugiol, ferruginol, saprorthoquinone, cryptomeriololide, and salvinolone.

InI3-catalyzed polyene cyclization of allenes and its application in the total synthesis of seven abietane-type diterpenoids

A novel polyene cyclization using the allene group as the initiator has been successfully developed. This methodology provides an efficient strategy for the construction of an abietane-type tricyclic skeleton with a functionalizable C2-C3 double bond and features a wide substrate scope and excellent stereoselectivities. Potential utility of this approach has been well demonstrated by the collective total synthesis of seven abietane-type diterpenoids. Specifically, (±)-2,3-dihydroxyferruginol and (±)-2,3-dihydroxy-15,16-dinor-ent-pimar-8,11,13-triene were synthesized for the first time.

Biologically Active Diterpenoids in the Clerodendrum Genus—A Review

One of the key areas of interest in pharmacognosy is that of the diterpenoids; many studies have been performed to identify new sources, their optimal isolation and biological properties. An important source of abietane-, pimarane-, clerodane-type diterpenoids and their derivatives are the members of the genus Clerodendrum, of the Lamiaceae. Due to their diverse chemical nature, and the type of plant material, a range of extraction techniques are needed with various temperatures, solvent types and extraction times, as well as the use of an ultrasound bath. The diterpenoids isolated from Clerodendrum demonstrate a range of cytotoxic, anti-proliferative, antibacterial, anti-parasitic and anti-inflammatory activities. This review describes the various biological activities of the diterpenoids isolated so far from species of Clerodendrum with the indication of the most active ones, as well as those from other plant sources, taking into account their structure in terms of their activity, and summarises the methods for their extraction.

New Antineoplastic Naphthohydroquinones Attached to Labdane and Rearranged Diterpene Skeletons

Terpenylquinones are mixed biogenesis primary or secondary metabolites widespread in Nature with many biological activities, including the antineoplastic cytotoxicity, that have inspired this work. Here, we present a cytotoxic structure-activity relationship of several diterpenylhydroquinone (DTHQ) derivatives, obtained from the natural labdane diterpenoid myrceocommunic acid used as starting material. Different structural modifications, that changed the functionality and stereochemistry of the decalin, have been implemented on the bicyclic core through epoxidation, ozonolysis or decarboxylation, and through induction of biomimetic breaks and rearrangements of the diterpene skeleton. All the isomers generated were completely characterized by spectroscopic procedures. The resulting compounds have been tested in vitro on cultured cancer cells, showing their relevant antineoplastic cytotoxicity, with GI₅₀ values in the μM and sub-μM range. The rearranged compound 8 showed the best cytotoxic results, with GI₅₀ at the submicromolar range, retaining the cytotoxicity level of the parent compounds. In this report, the versatility of the labdane skeleton for chemical transformation and the interest to continue using structural modifications to obtain new bioactive compounds are demonstrated.

Total Synthesis of Cryptotrione

The total synthesis of cryptotrione (1) was enabled by substrate-controlled diastereoselective construction of the bicyclo[3.1.0]hexene framework through platinum-catalyzed enyne cycloisomerization and Lewis acid induced polyene cyclization to construct the abietane-type tricyclic diterpene skeleton. The stereogenic tertiary carbon center in the side chain was installed in a diastereodivergent manner by conjugate addition reactions.

Synthesis and structure-activity relationships of novel abietane diterpenoids with activity against Staphylococcus aureus

Aim: To find alternative compounds against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA), novel derivatives from dehydroabietic acid were synthesized. Methods & results: Compound 12 was the most effective against 15 MRSA and 11 MSSA with minimum inhibitory concentration values ranging from 3.9 to 15.6 μg/ml. Although less active than 12, compound 11, followed by 25 and 13, also exhibited anti-staphylococcal activity. Additional studies showed that compound 12 is devoid of toxic effect on non-target cells. A structure-activity relationship study revealed that an oxime at C-13 together with a hydroxyl at C-12 could play a key role in the activity. Conclusion: These structures, in particular compound 12, could arise as templates for the development of agents against MRSA and MSSA.

Antibacterial effects of extracts obtained from plants of Argentina: Bioguided isolation of compounds from the anti-infectious medicinal plant Lepechinia meyenii

ETHNOPHARMACOLOGICAL RELEVANCE

The mostly native species from Argentina are used in traditional medicine generally for the treatment of pain and inflammation, respiratory, gastro-intestinal and urinary disorders and as antiseptics.

AIM OF THE STUDY

Since these ailments may be associated with bacterial infections and that it is necessary to discover alternative compounds with antibacterial activity, 69 extracts from these plants were screened for their activity against pathogenic bacteria. The most effective extract was then submitted to bioguided isolation to obtain the compounds responsible for this activity.

MATERIALS AND METHODS

Extracts and fractions were screened using agar dilution, and compounds using microbroth dilution methods. A large panel of pathogenic bacteria was used, especially methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA). Bioguided fractionation was performed using successive chromatographic techniques, while the chemical structures of the isolated compounds were determined by nuclear magnetic resonance (NMR). Additionally, a series of derivatives of the most active compound were prepared in order to study the chemical features required for achieving the antibacterial effect.

RESULTS

Lepechinia meyenii (Walp.) Epling (Lamiaceae) extract showed itself the most effective, with minimum inhibitory concentration (MIC) against Gram positive and negative bacteria ranging from 62.5 to 500 μg/mL, and showing better activity on MRSA than on MSSA. Activity-guided fractionation yielded the abietanes carnosol (1), rosmanol (2) and carnosic acid (3) as active principles, with MICs ranging from 15.6-31.2, 15.6-62.5 and 7.8-15.6 μg/mL, respectively against 15 MRSA strains, and 15.6-31.2, 31.2-62.5 and 7.8-15.6 μg/mL, respectively against 11 MSSA strains, maintaining higher activity against the resistant bacteria, as does the extract. In addition, Enterococcus faecalis was sensitive to 1-3 with MICs of 15.6-62.5 μg/mL. The structure activity analysis showed that 12-OH is necessary for remarkable activity, but methylation in C-20 significantly increased this, as observed with 20-methyl carnosate (5) displaying the greatest effect, even more so than 3, with MICs of 3.9 μg/mL against all the tested MRSA and 3.9-7.8 μg/mL against the MSSA.

CONCLUSIONS

The results of this study contribute to validate the traditional antibacterial use of species native to Argentina, particularly of L. meyenii. The chemical structures of the compounds obtained may aid the design of antibacterial agents, especially those effective against MRSA.

Ureido Derivatives of Neoabietic Acid

A series of ureido derivatives of neoabietic acid were synthesized by application of Curtius rearrangement reaction to neoabietic acid and amines. Structure characterization of these compounds was done by 1H-NMR, 13C-NMR and HRMS spectral analysis.

Sessein and isosessein with anti-inflammatory, antibacterial and antioxidant activity isolated from Salvia sessei Benth

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia sessei Benth, popularly known as "pipilolxochitl" or "sabanito", is a plant utilized in Mexico in traditional medicine for the treatment of erysipela. To date, only one report, to our knowledge, has been found in which a royleanone-type diterpene of the aerial parts of the species was isolated but, again to our knowledge, studies have not been conducted on the pharmacological activity of extracts and compounds isolated from this plant.

AIM OF THE STUDY

The objective of the study was to evaluate the anti-inflammatory, antibacterial and antioxidant activity of the organic extracts of the aerial parts of Salvia sessei Benth and sessein and isosessein isomers isolated from this.

MATERIALS AND METHODS

Anti-inflammatory activity was evaluated in a model of edema in mouse ear at 1 mg/ear of the isolated extracts and compounds (1 and 2), a dose-response curve was performed on these latter and one-half of the effective dose (ED₅₀) was determined; antibacterial activity was determined through minimal inhibitory concentration (MIC) by microdilution at 100, 50, 25, and 12.5 µg/mL, and antioxidant capacity, by means of DPPH, ABTS, and FRAP assays where, for the first two assays noted, the inhibitory concentration 50% (IC₅₀) was calculated for the extracts as well as for the compounds isolated.

RESULTS

The hexanic extracts (40.55 ± 0.5%), dichloromethanic (56.01 ± 1.1%) and methanolic (66.05 ± 0.3%), as well as isolated compounds 1 (79.85 ± 3.5%) and 2 (54.36 ± 1.7%), demonstrated anti-inflammatory activity; the methanolic extract presented the greatest percentage of inhibition, while isolated compounds 1 and 2 did not present a difference in their ED₅₀; additionally, compound 1 exerted a similar effect to that of the drug-of-reference at the same dose (75.24 ± 2.4%). The antibacterial activity of the extracts and compounds was principally against Gram-positive bacteria: the hexanic extract presented activity against Staphylococcus hominis and the methanolic and dichloromethanic extracts, and compound 1 exhibited activity against Staphylococcus haemolyticus, S. hominis, E. faecalis, in addition to that Escherichia coli was sensitive to compound 1, while isomer 2 showed activity against Staphylococcus aureus, Staphylococcus haemolyticus, Staphylococcus epidermis and Streptococcus pyogenes bacteria related to erysipela. In the three assays, the extract demonstrating greatest antioxidant capacity was the methanolic extract, while that of the isolated compounds was compound 1.

CONCLUSIONS

The results show that the three extracts evaluated in the three models presented activity and the chromatographic separation of the dichloromethanic extract permitted the isolation of compounds 1 and 2 royleanone-type isomers, which also presented significant activities such as anti-inflammatory, antibacterial and antioxidant, thus validate the use of this species in traditional medicine.

Crystal structure of (4bS,8aR)-1-isopropyl-4b,8,8-trimethyl-7-oxo-4b,7,8,8a,9,10-hexa-hydro-phenanthren-2-yl acetate

The title compound, C22H28O3, was prepared by a direct acetyl-ation reaction of naturally occurring totarolenone. The mol-ecule contains three fused rings, which exhibit different conformations. The central ring has a half-chair conformation, while the non-aromatic oxo-substituted ring has a screw-boat conformation. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π inter-actions, forming sheets parallel to the bc plane. The carbonyl O atoms and the C atom at the 6-position of the cyclo-hexene ring are each disordered over two sets of sites with major occupancy components of 0.63 (7) and 0.793 (14), respectively.

Efficient Separation of Four Antibacterial Diterpenes from the Roots of Salvia Prattii Using Non-Aqueous Hydrophilic Solid-Phase Extraction Followed by Preparative High-Performance Liquid Chromatography

An efficient preparative procedure for the separation of four antibacterial diterpenes from a Salvia prattii crude diterpenes-rich sample was developed. Firstly, the XION hydrophilic stationary phase was chosen to separate the antibacterial crude diterpenes-rich sample (18.0 g) into three fractions with a recovery of 46.1%. Then, the antibacterial fractions I (200 mg), II (200 mg), and III (150 g) were separated by the Megress C18 preparative column, and compounds tanshinone IIA (80.0 mg), salvinolone (62.0 mg), cryptotanshinone (70.0 mg), and ferruginol (68.0 mg) were produced with purities greater than 98%. The procedure achieved large-scale preparation of the four diterpenes with high purity, and it could act as a reference for the efficient preparation of active diterpenes from other plant extracts.

Crystal structure of 7β-hy-droxy-royleanone isolated from Taxodium ascendens (B.)

The title compound, C20H28O4 [systematic name: (4bS,8aS,10S)-3,10-dihy-droxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octa-hydro-phenanthrene-1,4-dione], is an abietane-type diterpene, which was isolated from Taxodium ascendens (B.). The compound crystallizes in the chiral space group P21, but it was not possible to determine the absolute structure of the mol-ecule in the crystal by resonant scattering. The mol-ecular structure is stabilized by two intra-molecular O-H⋯O hydrogen bonds, enclosing S(5) and S(6) ring motifs. In the crystal, mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds, forming chains along the [010] direction. The crystal structure of the 10R stereoisomer of the title compound, isolated from the roots of Premna obtusifolia (Verbenaceae), has been reported. It crystallized in the chiral space group P212121, and the absolute structure was determined as (4bS,8aS,10R), by resonant scattering using Cu Kα radiation [Razak et al. (2010 ▸). Acta Cryst. E66, o1566-o1567].

Crystal structure of taxodione isolated from Taxodium ascendens (B.)

The title compound [systematic name: (4bS)-4-hy-droxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a-hexa-hydro-phenanthrene-3,9-dione], C20H26O3, is an abietane-type diterpene, which was isolated from Taxodium ascendens (B.). In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming supra-molecular chains propagating along the [001] direction.

Abietane diterpenoids from Cephalotaxus lanceolata

A new abietane diterpenoid, 12-O-methyl-20-deoxocarnosol-3-one (1), and eight known abietane diterpenoids including 13-abietadien-12-one (2), 5,6-dehydrosugiol (3), sugiol (4), torreyayunnin (5), taxusabietane A (6), hinokiol (7), 3-acetoxyabieta-8,11,13-trien-12-ol (8), and martiusane (9) were obtained from leaves and twigs of Cephalotaxus lanceolata. The structures of isolated compounds (1-9) were determined based on analysis of their spectroscopic data and comparison with those reported in the literature. Compounds 3, 8 and 9 were first isolated from the plants of Cephalotaxus genus.

Discovery of novel phthalimide analogs: Synthesis, antimicrobial and antitubercular screening with molecular docking studies

In continuation of our endeavor towards the design and development of potent and effective antimicrobial agents, three series of phthalimide derivatives (4a-i, 5a-f, and 6a-c) were synthesized, fully characterized and evaluated for their potential antibacterial, antifungal and antimycobacterial activities. These efforts led to the discovery of nine compounds 4c, 4f, 4g, 4h, 4i, 5c, 5d, 5e, and 6c (MIC range from 0.49 to 31.5 μg/mL) with potent antibacterial, antifungal, and antimycobacterial activities. Ampicillin, ciprofloxacin, amphotericin B were used as references for antibacterial and antifungal screening respectively, while isoniazid was used as a reference for antimycobacterial testing. Furthermore, molecular modeling studies were done to explore the binding mode of the most active derivatives to M. tuberculosis enoyl reductase (InhA) and DNA gyrase B. Our study showed the importance of both hydrogen bonding and hydrophobic interactions as a key interaction with the target enzymes.

Abietane and nor-abitane diterpenoids from the roots of Salvia rhytidea

Background

The genus Salvia is a rich source of structurally diverse terpenoids. Different species of the Salvia have been used in folk medicine of Iran and therefore attracted the attention of researchers for exploring their chemical constituents. In a project directed at structurally interesting bioactive metabolites from Iranian Lamiaceae, we studied Salvia rhytidea.

Results

Fractionation of the petroleum ether extract of the root of S. rhytidea led to the isolation of a new 20-nor-abietane diterpenoid (1), together with seven known compounds, comprising five abietane diterpenoids (2–6), and two rearranged abietanes (7, 8). Their structures were established by a combination of 1D and 2D NMR.

Conclusions

Our results showed that the root of S. rhytidea could be considered as a new and rich source of different types of abietane and rearranged abietane diterpenoids.

An antibacterial ortho-quinone diterpenoid and its derivatives from Caryopteris mongolica

To identify antibacterial components in traditional Mongolian medicinal plant Caryopteris mongolica, an ortho-quinone abietane caryopteron A (1) and three its derivatives caryopteron B-D (2-4) were isolated from the roots of the plant together with three known abietanes demethylcryptojaponol (5), 6α-hydroxydemethyl cryptojaponol (6), and 14-deoxycoleon U (7). The chemical structures of these abietane derivatives were elucidated on the basis of spectroscopic data. Compounds 1-4 had C-13 methylcyclopropane substructures, and 2-4 had a hexanedioic anhydride ring C instead of ortho-quinone in 1. The stereochemistry of these compound was assumed from NOE spectra and ECD Cotton effects. Compounds 1 and 5-7 showed antibacterial activities against the Gram-positive bacteria Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and Micrococcus luteus, being 1 the more potent.

Aromatic abietane diterpenoids: their biological activity and synthesis

In this study, the biological properties of abietane-type diterpenoids with an aromatic C ring are reviewed. The review contains about 160 references.

Design, synthesis, molecular docking, and antibacterial evaluation of some novel flouroquinolone derivatives as potent antibacterial agent

Objective. Quinolone moiety is an important class of nitrogen containing heterocycles widely used as key building blocks for medicinal agents. It exhibits a wide spectrum of pharmacophores and has bactericidal, antiviral, antimalarial, and anticancer activities. In view of the reported antimicrobial activity of various fluoroquinolones, the importance of the C-7 substituents is that they exhibit potent antimicrobial activities. Our objective was to synthesize newer quinolone analogues with increasing bulk at C-7 position of the main 6-fluoroquinolone scaffold to produce the target compounds which have potent antimicrobial activity. Methods. A novel series of 1-ethyl-6-fluoro-4-oxo-7-{4-[2-(4-substituted phenyl)-2-(substituted)-ethyl]-1-piperazinyl}-1,4-dihydroquinoline-3-carboxylic acid derivatives were synthesized. To understand the interaction of binding sites with bacterial protein receptor, the docking study was performed using topoisomerase II DNA gyrase enzymes (PDB ID: 2XCT) by Schrodinger's Maestro program. In vitro antibacterial activity of the synthesized compounds was studied and the MIC value was calculated by the broth dilution method. Results. Among all the synthesized compounds, some compounds showed potent antimicrobial activity. The compound 8g exhibited good antibacterial activity. Conclusion. This investigation identified the potent antibacterial agents against certain infections.

Abietane diterpenoids from Salvia sclarea transformed roots as growth inhibitors of pathogenic Acanthamoeba spp

Amoebae from the genus Acanthamoeba are known agents leading to various diseases such as granulomatous amoebic encephalitis (GAE), a chronic progressive disease of the central nervous system, amoebic keratitis (AK), chronic eye infection, amoebic pneumitis (AP), chronic lung infection, and skin infections. It is known that various synthetic anti-Acanthamoeba substances are ineffective. Therefore, other substances, e.g., natural plant compounds, are the focus of biological investigations regarding anti-parasite activity. In this work, the ability of four abietane diterpenoids (ferruginol, salvipisone, aethiopinone, and 1-oxo-aethiopinone) to inhibit Acanthamoeba growth is reported. All investigated compounds were active against Acanthamoeba growing in vitro. Among them, ferruginol demonstrated the highest activity against Acanthamoeba. This compound inhibited Acanthamoeba growth by about 72% in a 3-day exposure period (IC50 17.45 μM), while aethiopinone and 1-oxo-aethiopinone demonstrated this activity at the level of 55-56%. Salvipisone reduced the growth of Acanthamoeba in vitro culture by 39%. For this compound, the value of IC50 was 701.94 μM after 72 h of exposure.

Synthetic derivatives of aromatic abietane diterpenoids and their biological activities

Naturally occurring aromatic abietane diterpenoids (dehydroabietanes) exhibit a wide range of biological activities. A number of synthetic studies aimed at modifying the abietane skeleton in order to obtain new potential chemotherapeutic agents have been reported. In this study, the biological activities of synthetic derivatives of aromatic abietane diterpenoids are reviewed.

Antibacterial activity of Taxodium ascendens Diterpenes against Methicillin-resistant Staphylococcus aureus

One new and seven known diterpenes were identified from an antibacterial chromatographic fraction of Taxodium ascendens. Of these, demethylcryptojaponol (2), 6-hydroxysalvinolone (3), hydroxyferruginol (4), and hinokiol (5) demonstrated potent activity against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). These compounds represent a class of synthetically accessible compounds that could be further developed for treatment of drug-resistant bacterial infections.

Taxodione and arenarone inhibit farnesyl diphosphate synthase by binding to the isopentenyl diphosphate site

We used in silico methods to screen a library of 1,013 compounds for possible binding to the allosteric site in farnesyl diphosphate synthase (FPPS). Two of the 50 predicted hits had activity against either human FPPS (HsFPPS) or Trypanosoma brucei FPPS (TbFPPS), the most active being the quinone methide celastrol (IC50 versus TbFPPS ∼ 20 µM). Two rounds of similarity searching and activity testing then resulted in three leads that were active against HsFPPS with IC50 values in the range of ∼ 1-3 µM (as compared with ∼ 0.5 µM for the bisphosphonate inhibitor, zoledronate). The three leads were the quinone methides taxodone and taxodione and the quinone arenarone, compounds with known antibacterial and/or antitumor activity. We then obtained X-ray crystal structures of HsFPPS with taxodione+zoledronate, arenarone+zoledronate, and taxodione alone. In the zoledronate-containing structures, taxodione and arenarone bound solely to the homoallylic (isopentenyl diphosphate, IPP) site, not to the allosteric site, whereas zoledronate bound via Mg(2+) to the same site as seen in other bisphosphonate-containing structures. In the taxodione-alone structure, one taxodione bound to the same site as seen in the taxodione+zoledronate structure, but the second located to a more surface-exposed site. In differential scanning calorimetry experiments, taxodione and arenarone broadened the native-to-unfolded thermal transition (Tm), quite different to the large increases in ΔTm seen with biphosphonate inhibitors. The results identify new classes of FPPS inhibitors, diterpenoids and sesquiterpenoids, that bind to the IPP site and may be of interest as anticancer and antiinfective drug leads.

(+)-Dehydroabietic acid, an abietane-type diterpene, inhibits Staphylococcus aureus biofilms in vitro

Potent drugs are desperately needed to counteract bacterial biofilm infections, especially those caused by gram-positive organisms, such as Staphylococcus aureus. Moreover, anti-biofilm compounds/agents that can be used as chemical tools are also needed for basic in vitro or in vivo studies aimed at exploring biofilms behavior and functionability. In this contribution, a collection of naturally-occurring abietane-type diterpenes and their derivatives was tested against S. aureus biofilms using a platform consisting of two phenotypic assays that have been previously published by our group. Three active compounds were identified: nordehydroabietylamine (1), (+)-dehydroabietic acid (2) and (+)-dehydroabietylamine (3) that prevented biofilm formation in the low micromolar range, and unlike typical antibiotics, only 2 to 4-fold higher concentrations were needed to significantly reduce viability and biomass of existing biofilms. Compound 2, (+)-dehydroabietic acid, was the most selective towards biofilm bacteria, achieving high killing efficacy (based on log Reduction values) and it was best tolerated by three different mammalian cell lines. Since (+)-dehydroabietic acid is an easily available compound, it holds great potential to be used as a molecular probe in biofilms-related studies as well as to serve as inspirational chemical model for the development of potent drug candidates.

Diterpenoids with anti-inflammatory activity from the wood of Cunninghamia konishii

Two new diterpenoids, konishone (1) and 3β-hydroxy-5,6-dehydrosugiol (2), along with three known diterpenoids—hinokiol (3), sugiol (4), and 12-hydroxy-6,7-secoabieta-8,11,13-triene-6,7-dial (5)—were isolated from the wood of Cunninghamia konishii. Compound 1 is a novel skeleton of the 7,20-dinorabietane-type diterpene. In addition, when RAW264.7 macrophages were treated with different concentrations of compounds 1, 3, and 5 together with LPS, a significant concentration-dependent inhibition of NO production was detected. The IC₅₀ values for inhibition of nitrite production of compounds 1, 3, and 5 were about 9.8 ± 0.7, 7.9 ± 0.9, and 9.3 ± 1.3 μg/mL, respectively. This study presents the potential utilization of compounds 1, 3, and 5, as lead compounds for the development of anti-inflammatory drugs.

Antimicrobial and anti-biofilm properties of new taxodione derivative from hairy roots of Salvia austriaca

The aim of the present report was to evaluate antimicrobial/anti-biofilm activity of 7-(2-oxohexyl)-taxodione, a novel taxodione derivative isolated from n-hexane extract of Salvia austriaca hairy roots. Antimicrobial assays showed that 7-(2-oxohexyl)-taxodione was at least 4 times more active than taxodione against methicillin-susceptible as well against methicillin-resistant staphylococci with MIC of 1.25-2.5 μgml(-1). This compound was less active against vancomycin-resistant enterococci (VRE), on the same level as taxodione (MIC ranged 10.0-20.0 μgml(-1)). The presence of 7-(2-oxohexyl)-taxodione in the culture medium (at MIC, ½ MIC or ¼ MIC) decreased adhesion of staphylococci to abiotic surfaces, which in turn caused a reduction in biofilm formation during 24h, by approximately 25-30%. Also, the extent of established biofilm eradication was found to be significant, although it required an increased concentration of the compound. This is the first report on the antimicrobial activity of this, up to now not known compound, isolated from transformed roots of S. austriaca.