Inhibitors of skin-tumor promotion. VIII. Inhibitory effects of euglobals and their related compounds on Epstein-Barr virus activation. (1)

Antiviral and antibacterial properties of phloroglucinols: a review on naturally occurring and (semi)synthetic derivatives with potential therapeutic interest

Phloroglucinol and derived compounds comprise a huge class of secondary metabolites widely distributed in plants and brown algae. A vast array of biological activities, including antioxidant, anti-inflammatory, antimicrobial, and anticancer has been associated to this class of compounds. In this review, the available data on the antiviral and antibacterial capacity of phloroglucinols have been analyzed. Some of these compounds and derivatives show important antimicrobial properties in vitro. Phloroglucinols have been shown to be effective against viruses, such as human immunodeficiency virus (HIV), herpes or enterovirus, and preliminary data through docking analysis suggest that they can be effective against SARS-CoV-19. Also, some phloroglucinols derivatives have shown antibacterial effects against diverse bacteria strains, including Bacillus subtilis and Staphylococcus aureus, and (semi)synthetic development of novel compounds have led to phloroglucinols with a significantly increased biological activity. However, therapeutic use of these compounds is hindered by the absence of in vivo studies and scarcity of information on their mechanisms of action, and hence further research efforts are required. On the basis of this consideration, our work aims to gather data regarding the efficacy of natural-occurring and synthetic phloroglucinol derivatives as antiviral and antibacterial agents against human pathogens, which have been published during the last three decades. The recollection of results reported in this review represents a valuable source of updated information that will potentially help researchers in the development of novel antimicrobial agents.

Phloroglucinols with hAChE and α-glucosidase inhibitory activities from the leaves of tropic Rhodomyrtus tomentosa

Four undescribed phloroglucinol meroterpenoids, rhodotomentodiones A-D, and one undescribed phloroglucinol dimer, rhodotomentodimer A, were obtained and structurally established from tropic Rhodomyrtus tomentosa leaves. Their structures were unambiguously elucidated based on the comprehensive analyses of the NMR and MS spectroscopic data, electronic circular dichroism (ECD) calculation, and single-crystal X-ray diffraction. In particular, rhodotomentodiones A and B represent the first examples of phloroglucinol meroterpenoids featuring a unique γ-pyranoid moiety. More importantly, rhodotomentodimer A exhibited the most potential human acetylcholinesterase (hAChE) and α-glucosidase inhibitory effects with IC₅₀ values of 7.5 μM and 5.6 μM, respectively. The possible interaction sites of the above potential hAChE and α-glucosidase inhibitor were achieved by molecular docking studies. These findings greatly enrich the diversity of natural products from Myrtaceae species, and provide potential candidates for the further development of anti-Alzheimer and antidiabetic diseases.

Phloroglucinol Mediated Plant Regeneration of Ornithogalum dubium as the Sole "Hormone-Like Supplement" in Plant Tissue Culture Long-Term Experiments

Tissue culture is an essential requirement in plant science to preserve genetic resources and to expand naturally occurring germplasm. A variety of naturally occurring and synthetic hormones are available to induce the processes of dedifferentiation and redifferentiation. Not all plant material is susceptible to tissue culture, and often complex media and hormone requirements are needed to achieve successful plant propagations. The availability of new hormones or chemicals acting as hormones are critical to the expansion of tissue culture potentials. Phloroglucinol has been shown to have certain hormone-like properties in a variety of studies. Ornithogalum dubium, an important geophyte species, was used to characterise the potential of phloroglucinol as the sole plant-like hormone in a tissue culture experiment. Tissue culture, plant regeneration, total phenolic and genetic variability were established by applying a variety of methods throughout long-term experiments. Phloroglucinol did induce callus formation and plant regeneration when used as the sole supplement in the media at a rate of 37%, thus demonstrating auxin/cytokines-like properties. Callus formation was of 3 types, friable and cellular, hard and compact, and a mixture of the two. The important finding was that direct somatogenesis did occur albeit more frequently on younger tissue, whereby rates of induction were up to 52%. It is concluded that phloroglucinol acts as a "hormone-like" molecule and can trigger direct embryogenesis without callus formation.

The effect of alcoholic extract from Eucalyptus camaldulensis leaves on HTLV-1 Tax activities

HTLV-1 is a human retrovirus responsible for adult T-cell leukemia (ATL) and certain other clinical disorders. The viral Tax oncoprotein plays a central role in HTLV-1 pathogenicity, mainly due to its capacity of inducing the transcriptional activity of various transcriptional factors like NFқB. Eucalyptus camaldulensis (Ec) is considered as a traditional medicinal plant with valuable therapeutic effects. Here we evaluated the activity of its ethanolic leave extract on different Tax activities by testing its influence on Tax-induced activity of NFқB and HTLV-1 LTR in Jurkat cells. Our results showed that Ec inhibited Tax induced activation of NFқB -, SRF- dependent promoters and HTLV-1 LTR. Ec extract has no effect on the binding of Tax to NFқB while it strongly prevented the degradation of IҝBα induced by Tax probably as a result of preventing the link between Tax and IKKγ. In addition, increasing the cellular level of P-TEFb-cyclinT1 significantly reduced the inhibitory effect of Ec on Tax activities, probably by preventing the interaction between Tax and P-TEFb-cyclin T1. The 40%-MeOH fraction of this extract, which is rich with polyphenols, offered the highest inhibitory effect against Tax activities. Further studies are required for the isolation and identification of active component/s in this extract which may be developed in the future as preventive/curing drugs for HTLV-1 related diseases.

RNA-seq-based quanitative transcriptome analysis of meat color and taste from chickens administered by eucalyptus leaf polyphenols extract

To evaluate how eucalyptus leaf polyphenol extract (EPE) affects chicken meat color and taste, we added different levels of EPE (0%, 0.06%, 0.09%, and 0.12%) to chicken feed. The redness (a^* value) and the myoglobin content of breast muscle in EPE group were remarkably higher. Furthermore, the guanosine monophosphate, histidine, and glycine muscle contents were also enhanced. Transcriptome analysis showed that 10 candidate genes related to meat quality were affected by EPE treatment. The identified genes, with functions critical to chicken meat color and taste, will help to determine the molecular mechanisms of EPE.

An Array of Bioactive Compounds From Australian Eucalypts and Their Relevance in Pancreatic Cancer Therapeutics

Pancreatic cancer (PC) is one of the most devastating human cancers, and despite the significant advances in the current therapeutic options, the overall survival rate for PC has remained static for the past 50 years. Plant-derived bioactive compounds play a vital role in cancer therapeutics by providing new lead compounds for future drug development. Therefore, the isolation, characterization, and identification of new bioactive compounds for the prevention and treatment of cancer continue to be an important aspect of natural product research. Many in vitro and in vivo studies published in the last few decades have established strong links between the phytochemical profile of eucalypts and anticancer activity. However, only a small number of these reports have attempted to demonstrate a relationship between the biological activity of eucalypt extracts and PC. This review focuses on potential anti-PC effects of an array of bioactive compounds present in various species of eucalypts. It also highlights the necessity for further in vitro and in vivo studies to develop a complete understanding of the potential this group of plants has for the development of potent and specific chemotherapeutic drugs for PC.

Phloroglucinol Derivatives from the Fruits of Eucalyptus globulus and Their Cytotoxic Activities

A new phloroglucinol derivative, named eucalyptin B (1), along with five related known compounds (2 - 6), was isolated from the fruits of Eucalyptus globulus. Their structures were elucidated by means of 1D- and 2D-NMR spectroscopy, with the absolute configuration of 1 determined by electronic circular dichroism (ECD) calculations. All isolated compounds (1 - 6) were evaluated for their cytotoxic activities against lung (A549), breast (4T1), and skin (B16F10) cancer cell lines. On the basis of cell viability assay, the cytotoxic activity of eucalyptin B (1) was further confirmed by apoptosis assay. Additionally, after treatment with eucalyptin B (1), the apoptosis factor proteins (Bcl2 and Bax) and caspase-3 levels in A549 cells were also determined by Western-blot analysis. By cytotoxic assay, eucalyptin B (1) exhibited potent cytotoxicity against A549 cells with an IC₅₀ value of 1.51 μm and induced concentration dependent apoptosis of up to 49%. Additionally, eucalyptin B (1) inhibited 5-fold and increased 10-folds in the level of Bcl2 and Bax, respectively. Furthermore, the 11-fold increase in the level of caspase-3 confirmed eucalyptin B (1) activated caspase dependent apoptosis pathway. In conclusion, the isolated compound eucalyptin B (1) has promising cytotoxic activity in tumor cells, especially in A549.

Molecular cloning, expression, and characterization of acyltransferase from Pseudomonas protegens

The formation of C-C bonds by using CoA independent acyltransferases may have significant impact for novel methods for biotechnology. We report the identification of Pseudomonas strains with CoA-independent acyltransferase activity as well as the heterologous expression of the enzyme in E. coli. The cloning strategies and selected expression studies are discussed. The recombinant acyltransferases were characterized with regard to thermal and storage stability, pH,- and co-solvent tolerance. Moreover, the impact of bivalent metals, inhibitors, and other additives was tested. Careful selection of expression and working conditions led to obtain recombinant acyltransferase form Pseudomonas protegens with up to 11 U mL^-1 activity.

Biological, medicinal and toxicological significance of Eucalyptus leaf essential oil: a review

The genus Eucalyptus L'Heritier comprises about 900 species, of which more than 300 species contain volatile essential oil in their leaves. About 20 species, within these, have a high content of 1,8-cineole (more than 70%), commercially used for the production of essential oils in the pharmaceutical and cosmetic industries. However, Eucalyptus is extensively planted for pulp, plywood and solid wood production, but its leaf aromatic oil has astounding widespread biological activities, including antimicrobial, antiseptic, antioxidant, chemotherapeutic, respiratory and gastrointestinal disorder treatment, wound healing, and insecticidal/insect repellent, herbicidal, acaricidal, nematicidal, and perfumes, soap making and grease remover. In the present review, we have made an attempt to congregate the biological ingredients of leaf essential oil, leaf oil as a natural medicine, and pharmacological and toxicological values of the leaf oil of different Eucalyptus species worldwide. © 2017 Society of Chemical Industry.

Eucarobustols A-I, Conjugates of Sesquiterpenoids and Acylphloroglucinols from Eucalyptus robusta

Nine new conjugates of sesquiterpenoids and acylphloroglucinols, named eucarobustols A-I (1-9), as well as 11 known analogues were isolated from the leaves of Eucalyptus robusta. The sesquiterpenoid motifs furnishing the new conjugates included four structural types of aristolane (1 and 2), guaiane (3), eudesmane (4), and aromadendrane (5-9) moieties. Compounds 1 and 2 were found to represent the first examples of conjugates of aristolane and acylphloroglucinol units. In turn, compound 3 features a new coupling model of guaiane and acylphloroglucinol via the C-4-C-7' bond. Compounds 1, 7, and 9 showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 1.3, 1.8, and 1.6 μM, respectively.

An atom-economical and stereoselective domino synthesis of functionalised dienes

Open sesame: A direct synthesis of functionalised and stereodefined dienes, relying on a domino allylic alkylation/electrocyclic ring-opening sequence, is reported. This method allows concise access to doubly vinylogous esters. A further systematic study of ring-opening rates of carbon-substituted cyclobutenes allowed the design of substrates amenable to sequential pericyclic reactions (see scheme).

Bioactive Lignans from the Leaves and Stems of Schisandra wilsoniana

Three new dibenzocyclooctadiene lignans, marlignans M–O (1–3), together two known ones, were isolated from the leaves and stems of Schisandra wilsoniana. The structures of 1–3 were elucidated by spectroscopic methods, including extensive 1D- and 2D-NMR techniques. Compound 2 showed anti-HIV-1 activity with an EC50 value of 5.82 μg/mL and a therapeutic index (TI) of more than 12.8. Compound 3 showed obvious bioactivity in inhibiting Epstein-Barr virus early antigen (EBV-EA) activation.

Potent HGF/c-Met axis inhibitors from Eucalyptus globulus: the coupling of phloroglucinol and sesquiterpenoid is essential for the activity

Eucalyptin A (1), together with two known compounds 2 and 3 exhibiting potent inhibition on HGF/c-Met axis, was discovered from the fruits of Eucalyptus globulus. 1 possessed an unprecedented carbon framework of phloroglucinol-coupled sesquiterpenoid, and its structure was elucidated by spectroscopic method and ECD calculation. A brief structure-activity relationship discussion indicated that the coupling of a phloroglucinol and a sesquiterpenoid is essential for the activity.

Two new euglobals from the leaves of Eucalyptus robusta

Two new euglobals, R1 (1) and R2 (2), together with eight known euglobals (3-10) were isolated from the leaves of Eucalyptus robusta. Their structures were established by means of spectroscopic analysis and single-crystal X-ray diffraction. Euglobal R1 (1) represents a new skeleton of formyl-isovaleryl phloroglucinol-coupled β-phellandrene.

Eucalyptals D and E, new cytotoxic phloroglucinols from the fruits of Eucalyptus globulus and assignment of absolute configuration

Two new phloroglucinols, named eucalyptals D (1) and E (2), along with a related known compound (euglobal-In-3, 3) were isolated from the fruits of Eucalyptus globulus. Their structures were established on the basis of extensive spectroscopic studies, revealing that they share a common 3,5-diformyl-isopentyl phloroglucinol unit, but each is instead coupled to a different sesquiterpenoid skeleton (aromadendrene in 1, cadinene in 2, and a spirosesquiterpene in 3). Compound 1 possessed an unusual seven-membered D ring with an ether bridge between C-2 of the aromadendrene moiety and C-2' of the aromatic unit. The absolute configuration of the isolates was defined by the comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1-3 exhibited significant in vitro cytotoxicities against a few human cancer cell lines (Huh-7, Jurkat, BGC-823, and KE-97) using the CellTiter-Glo^™ luminescent cell viability assay method.

Euglobal-IIIa, a novel acylphloroglucinol-sesquiterpene derivative from Eucalyptus robusta: absolute structure and cytotoxicity

Euglobal-IIIa (1), a novel acylphloroglucinol-sesquiterpene derivative, and a known analogue, have been isolated from leaves of Eucalyptus robusta. The structures was elucidated by extensive spectroscopic data and by comparison with data reported in literature, while the absolute configuration of 1 was determined by the X-ray diffraction analysis. Compound 1 exhibited comparable cytotoxicity with that of cisplatin against five human cancer cell lines HL-60, SMMC-7721, A-549, MCF-7, and SW480 with IC₅₀ values of 15.7, 15.5, 17.6, 14.3, and 21.8 µM, respectively.

Antibacterial sideroxylonals and loxophlebal A from Eucalyptus loxophleba foliage

Loxophlebal A, a new antibacterial formylated phloroglucinol was isolated from the mother liquor obtained after separation of sideroxylonals from the chloroform-methanol extract of leaves of Eucalyptus loxophleba ssp lissophloia. The structure of loxophlebal A was determined to be 3-desformyl sideroxylonal A by spectroscopic methods including 1D- and 2D-NMR. The stereochemistry of loxophlebal A was determined by chemical correlation with sideroxylonal A. This article also reports an efficient, simple and economic method for large scale isolation of sideroxylonals in a purity of >90% from the leaves of Eucalyptus loxophleba ssp lissophloia.

Cancer preventive agents 10. Prenylated dehydrozingerone analogs as potent chemopreventive agents

Dehydrozingerone analogs and related compounds were screened as potential antitumor promoters by using the in vitro short-term 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced Epstein-Barr virus early antigen activation assay. Among the 40 synthesized compounds, the prenylated analogs 16 and 34-36 showed the most significant and promising activity (100% inhibition of activation at 1 x 10(3) mol ratio/TPA, and 82-80%, 37-35%, and 13-11% inhibition at 5 x 10(2), 1 x 10(2), and 1 x 10 mol ratio/TPA, respectively) in this screening. Their activity profiles were comparable to those of the reference standard curcumin. While a prenyl moiety conferred potent chemopreventive activity, an extended prenyl unit such as a farnesyl moiety did not improve activity. Because in vitro inhibitory effects in this assay generally correlate well with in vivo inhibitory effects on tumor promotion, our results strongly suggested that prenylated 16 and 34-36 are likely to be promising antitumor promoters.

Phloroglucinol glycosides from the fresh fruits of Eucalyptus maideni

Five new phloroglucinol glycosides, eucalmainosides A-E (1-5), were isolated from the fresh fruits of Eucalyptus maideni, along with 15 flavonoids (6-20), seven (+)-oleuropeic acid derivatives (15, 16, and 22-26), three hydrolyzable tannins (32-34), and six simple phenolic compounds (21, 27-31). Their structures were determined on the basis of spectroscopic analyses, including HSQC, HMBC, and acidic hydrolysis. The in vitro anti-herpes simplex virus 1 (HSV-1) assay indicated that the flavonols, myricetin (6) and quercetin (7), and the ellagitannin isocoriariin F (33) showed weak anti-HSV-1 activity with TIC values of 0.31, 0.33, and 0.12 mM, respectively.

Eucalyptus leaf extract inhibits intestinal fructose absorption, and suppresses adiposity due to dietary sucrose in rats

Sucrose is more lipogenic than starch, and the extreme ingestion of sucrose induces adiposity and obesity. The aim of this study was to examine the effect of the eucalyptus (Eucalyptus globulus) leaf extract (ELE) on adiposity due to dietary sucrose in rats. In addition, in this study, the effect of ELE on intestinal fructose absorption was also examined. Rats were fed a high-sucrose diet (75 % in calorie base) with or without ELE (10 g/kg diet) for 5 weeks. Body weight was lower in the rats receiving ELE than in the controls (342 (sd 37·9)v. 392 (sd 26·0) g (n7);P<0·05). Furthermore, ELE resulted in decreases in the triacylglycerol concentrations in the plasma (1·44 (sd 0·448)v.2·79 (sd 0·677) mmol/l (n7);P<0·05) and liver (19·1 (sd 5·07)v.44·1 (sd 16·28) μmol/g (n7);P<0·05). In contrast, ELE did not show any significant effects in the rats fed a starch diet. When rats were orally given ELE 10 min before fructose administration, the intestinal fructose absorption, which was examined by measuring the elevated concentration of fructose in the portal vein at 30 min after the fructose administration, was significantly inhibited in a dose-dependent manner. Furthermore, in rats fed a high-fructose diet, the plasma and hepatic triacylglycerol concentrations were significantly decreased by ELE. These results indicate that ELE, which inhibits the intestinal fructose absorption, can suppress adiposity in rats that ingest large amounts of sucrose or fructose.

Biomimetic synthesis, antimicrobial, antileishmanial and antimalarial activities of euglobals and their analogues

In the present communication, naturally occurring phloroglucinol-monoterpene adducts, euglobals G1-G4 (3b/a and 4a/b) and 16 new analogues (13a/b-18a/b and 19-22) were synthesized by biomimetic approach. These synthetic compounds differ from natural euglobals in the nature of monoterpene and acyl functionality. All of these compounds were evaluated for their antibacterial, antifungal, antileishmanial and antimalarial activities. Analogue 17b possessed good antibacterial activity against methicillin-resistant Staphylococcus aureus, while analogues 19-22 possessed potent antifungal activity against Candida glabrata with IC50s ranging from 1.5 to 2.5 microg/mL. Euglobals along with all synthesized analogues exhibited antileishmanial activity. Amongst these, euglobal G2 (3a), G3 (4a) and analogues 13a and 14a showed potent antileishmanial activity with IC50s ranging from 2.8 to 3.9 microg/mL. Analogue 16a possessed antimalarial activity against chloroquine sensitive D6 clone of Plasmodium falciparum. None of the compounds showed toxicity against mammalian kidney fibroblasts (vero cells) upto the concentration of 4.76 microg/ml.

Triketones active against antibiotic-resistant bacteria: Synthesis, structure–activity relationships, and mode of action

A series of acylated phloroglucinols and triketones was synthesized and tested for activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VRE) and multi-drug-resistant Mycobacterium tuberculosis (MDR-TB). A tetra-methylated triketone with a C12 side chain was the most active compound (MIC of around 1.0 microg/ml against MRSA) and was shown to stimulate oxygen consumption by resting cell suspensions, suggesting that the primary target was the cytoplasmic membrane.

Antiherbivore chemistry of Eucalyptus-cues and deterrents for marsupial folivores

Formylated phloroglucinol compounds (FPCs) are the single most important factor determining the amount of foliage that marsupial folivores eat from individual Eucalyptus trees. Folivores need to recognize which trees contain FPCs if they are to avoid them and forage efficiently, they are challenged by great diversity in the types and quantities of FPCs present, even within eucalypt species. We investigated the relationship between FPCs and terpenoids in species with both simple and complex FPC profiles and found strong positive correlations between terpenes generally, and several monoterpenes in particular, and FPCs. Terpene cues also indicated qualitative differences in trees' FPC profiles. We describe significant qualitative and quantitative variation in FPCs in several species that are important food sources for marsupial folivores. New discoveries include the fact that macrocarpals occur as two major, distinct groups and several new dimeric acylphloroglucinols from Eucalyptus strzeleckii. These patterns add to the chemical complexity of the foraging environment for folivores.

An Efficient Two-Step Synthesis of Jensenone Isolated from Eucalyptus jensenii. Synthesis of Analogues and Evaluation as Antioxidants

A phloroglucinol derivative, jensenone (1) isolated from leaves of Eucalyptus jensenii has been synthesized for the first time through a short and efficient two-step procedure starting from commercially available phloroglucinol. The methodology provides a simplified route to introduce diformyl moiety for synthesis of biologically active formylated phloroglucinol compounds such as antimalarial robustadials, cancer chemopreventive euglobals, and antifouling sideroxylonals. Several analogues of jensenone have also been synthesized and evaluated for antioxidant capacity.

Antitumor agents 220. Antitumor-promoting effects of cimigenol and related compounds on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis

Cimigenol (1) and 39 related compounds were screened as potential antitumor promoters by examining the ability of the compounds to inhibit Epstein-Barr virus early antigen (EBV-EA) activation (induced by 12-O-tetradecanoylphorbol-13-acetate) in Raji cells. Structure-activity relationship analysis indicated that compound 1 showed the highest activity and also exhibited significant inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. These data suggest that 1 and the related compounds might be valuable anti-tumor promoters.

Chemopreventive potential of cyclic diarylheptanoids

Eleven cyclic diarylheptanoids and seven related compounds were screened as potential antitumor promoters by using the in vitro short-term 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced Epstein-Barr virus early antigen (EBV-EA) activation assay. In addition, the cyclic diarylheptanoid myricanone (2) was examined for antitumor initiating activity in a two-stage carcinogenesis assay of mouse skin tumors induced by peroxynitrite as an initiator and TPA as a promoter. Myricanone (2) exhibited significant antitumor-initiating effect on mouse skin. These data suggest that cyclic, as well as linear, diarylheptanoids might be valuable chemopreventors.

Antitumor-promoting effects of cyclic diarylheptanoids on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis

Eleven cyclic diarylheptanoids were screened as potential antitumor promoters by examining the ability of the compounds to inhibit Epstein-Barr virus early antigen activation (induced by 12-O-tetradecanoylphorbol-13-acetate) in Raji cells. 13-Oxomyricanol and myricanone showed the highest activity and also exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. These data suggest that certain diarylheptanoids might be valuable antitumor promoters and/or chemopreventors.

Hydrolyzable tannins and related polyphenols from Eucalyptus globulus

Eucaglobulin (1), a new complex of gallotannin and monoterpene, was isolated from the leaves of Eucaloptus globulus. Its structure was elucidated on the basis of spectral data. Four known hydrolyzable tannins [tellimagrandin I (2), eucalbanin C (3), 2-O-digalloyl-1,3,4-tri-O-galloyl-beta-D-glucose (4), 6-O-digalloyl-1,2,3-tri-O-galloyl-beta-D-glucose (5)], as well as gallic acid (6) and (+)-catechin (7), were also isolated. The antibacterial effects of some of these compounds were examined.

An antitumor promoter from Moringa oleifera Lam

In the course of studies on the isolation of bioactive compounds from Philippine plants, the seeds of Moringa oleifera Lam. were examined and from the ethanol extract were isolated the new O-ethyl-4-(alpha-L-rhamnosyloxy)benzyl carbamate (1) together with seven known compounds, 4(alpha-L-rhamnosyloxy)-benzyl isothiocyanate (2), niazimicin (3), niazirin (4), beta-sitosterol (5), glycerol-1-(9-octadecanoate) (6), 3-O-(6'-O-oleoyl-beta-D-glucopyranosyl)-beta-sitosterol (7), and beta-sitosterol-3-O-beta-D-glucopyranoside (8). Four of the isolates (2, 3, 7, and 8), which were obtained in relatively good yields, were tested for their potential antitumor promoting activity using an in vitro assay which tested their inhibitory effects on Epstein-Barr virus-early antigen (EBV-EA) activation in Raji cells induced by the tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). All the tested compounds showed inhibitory activity against EBV-EA activation, with compounds 2, 3 and 8 having shown very significant activities. Based on the in vitro results, niazimicin (3) was further subjected to in vivo test and found to have potent antitumor promoting activity in the two-stage carcinogenesis in mouse skin using 7,12-dimethylbenz(a)anthracene (DMBA) as initiator and TPA as tumor promoter. From these results, niazimicin (3) is proposed to be a potent chemo-preventive agent in chemical carcinogenesis.

Bioactive acylphloroglucinol derivatives from Eucalyptus species

The acyphloroglucinol derivatives produced by Eucalyptus species are reviewed. Aspects of their chemistry, stereochemistry, biological activity and biogenesis are discussed.

Inhibitory effects of 3-nitrophloroglucinecarboxylic acid derivatives on Epstein-Barr virus early antigen induction

The inhibitory effects of two series of 3-nitrophloroglucinecarboxylic acid derivatives, 3-nitro-2,4,6-trihydroxythiobenzamides (II) and 3-nitro-phloroglucinecarboxylates (III), on Epstein-Barr virus early antigen (EBV-EA) induction were examined using Raji cells. Some of them strongly inhibited the induction, N-nonyl and O-decyl derivatives being the most potent inhibitors among the thioamides and esters, respectively. These results suggest the possibility that these two 3-nitrophloroglucinecarboxylic acid derivatives may be listed as novel inhibitors of tumor promotion.

Inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen induction

Inhibitory effects of a series of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen (EBV-EA) induction were examined using Raji cells. Some of the tested compounds showed highly inhibitory activity, the N-octyl amide derivative being the most active among them. These results suggest the possibility that 3-nitro-2,4,6-trihydroxybenzamides might be listed as novel inhibitors of tumor promotion.