Iridoid and seco-iridoid glucosides from Chioccoca alba (Rubiaceae)

Methanolic Extracts of Chiococca alba in Aedes aegypti Biorational Management: Larvicidal and Repellent Potential, and Selectivity against Non-Target Organisms

The use of formulations containing botanical products for controlling insects that vector human and animal diseases has increased in recent years. Plant extracts seem to offer fewer risks to the environment and to human health without reducing the application strategy's efficacy when compared to synthetic and conventional insecticides and repellents. Here, we evaluated the potential of extracts obtained from caninana, Chiococca alba (L.) Hitchc. (Rubiaceae), plants as a tool to be integrated into the management of Aedes aegypti, one of the principal vectors for the transmission of arborviruses in humans. We assessed the larvicidal and repellence performance against adult mosquitoes and evaluated the potential undesired effects of the extracts on non-target organisms. We assessed the susceptibility and predatory abilities of the nymphs of Belostoma anurum, a naturally occurring mosquito larva predator, and evaluated the C. alba extract's cytotoxic effects in mammalian cell lines. Our chromatographic analysis revealed 18 compounds, including rutin, naringin, myricetin, morin, and quercetin. The methanolic extracts of C. alba showed larvicidal (LC₅₀ = 82 (72-94) mg/mL) activity without killing or affecting the abilities of B. anurum to prey upon mosquito larvae. Our in silico predictions revealed the molecular interactions between rutin and the AeagOBP1 receptor to be one possible mechanism for the repellent potential recorded for formulations containing C. alba extracts. Low cytotoxicity against mammalian cell lines reinforces the selectivity of C. alba extracts. Collectively, our findings highlight the potential of C. alba and one of its constituents (rutin) as alternative tools to be integrated into the management of A. aegypti mosquitoes.

Identification and functional characterization of three iridoid synthases in Gardenia jasminoides

The discovery of three iridoid synthases (GjISY, GjISY2 and GjISY4) from Gardenia jasminoides and their functional characterization increase the understanding of iridoid scaffold/iridoid glycoside biosynthesis in iridoid-producing plants. Iridoids are a class of noncanonical monoterpenes that are found naturally in the plant kingdom mostly as glycosides. Over 40 iridoid glycosides (e.g., geniposide, gardenoside and shanzhiside) have been isolated from Gardenia jasminoides. They have multiple pharmacological properties and health-promoting effects. However, their biosynthetic pathway is poorly understood, and the iridoid synthase (ISY) responsible for the cyclization of the core scaffold remains unclear. In this study, three homologs of ISYs from G. jasminoides (GjISY, GjISY2 and GjISY4) were identified on the basis of transcriptomic data and functionally characterized. The genomic structure and intron-exon arrangement revealed that all three ISYs contained an intron. Biochemical assays indicated that all three recombinant enzymes reduced 8-oxogeranial to nepetalactol and its open forms (iridodials) as the products of the classical CrISY (Catharanthus roseus). In addition, all three enzymes reduced progesterone to 5-β-prognane-3,20-dione. However, only GjISY2 and GjISY4 reduced 2-cyclohexen-1-one to cyclohexanone. Overall, the GjISY2 expression levels in the flowers and fruits were similar to the GjISY and GjISY4 expression levels. By contrast, the GjISY2 expression levels in the upper and lower leaves were substantially higher than the GjISY and GjISY4 expression levels. Among the three, GjISY2 exhibited the highest catalytic efficiency for 8-oxogeranial. GjISY2 might be the major contributor to iridoid biosynthesis in G. jasminoides. Collectively, our results advance the understanding of iridoid scaffold/iridoid glycoside biosynthesis in G. jasminoides and provide a potential target for metabolic engineering and breeding.

Genome assembly of Chiococca alba uncovers key enzymes involved in the biosynthesis of unusual terpenoids

Chiococca alba (L.) Hitchc. (snowberry), a member of the Rubiaceae, has been used as a folk remedy for a range of health issues including inflammation and rheumatism and produces a wealth of specialized metabolites including terpenes, alkaloids, and flavonoids. We generated a 558 Mb draft genome assembly for snowberry which encodes 28,707 high-confidence genes. Comparative analyses with other angiosperm genomes revealed enrichment in snowberry of lineage-specific genes involved in specialized metabolism. Synteny between snowberry and Coffea canephora Pierre ex A. Froehner (coffee) was evident, including the chromosomal region encoding caffeine biosynthesis in coffee, albeit syntelogs of N-methyltransferase were absent in snowberry. A total of 27 putative terpene synthase genes were identified, including 10 that encode diterpene synthases. Functional validation of a subset of putative terpene synthases revealed that combinations of diterpene synthases yielded access to products of both general and specialized metabolism. Specifically, we identified plausible intermediates in the biosynthesis of merilactone and ribenone, structurally unique antimicrobial diterpene natural products. Access to the C. alba genome will enable additional characterization of biosynthetic pathways responsible for health-promoting compounds in this medicinal species.

7α-Hydroxyfriedelan-3-one-26-ol-29-oic acid and other Constituents from Pileostegia viburnoides var. glabrescens

Phytochemical investigation of the roots and rhizomes of Pileostegia viburnoides var. glabrescens led to the isolation and identification of 31 compounds (1-31), 25 of which (1-2, 4-7, 9-12, 15-18, 21-31) were isolated from the Pileostegia genus for the first time. 7α-Hydroxyfriedelan-3-one-26-ol-29-oic acid (1) is a new friedelane-type triterpene. The structure of n-butyl-β-D-fructopyranoside (2) was determined by single-crystal X-ray diffraction. Compounds 4 and 12 displayed marginal cytotoxicity against the P388 murine leukemia cell line with IC50 values of 13.4 μM and 25.0 μM, respectively. Compound 23 exhibited marginal anti-inflammatory activity by the inhibition of lipopolysaccharide induced nitric oxide production in RAW 264.7 macrophage cells, with an IC50 value of 32.0 μM. Compounds 3, 8-10, 25, and 27 were phytotoxic to the dicot Lactuca sativa (lettuce) and/or the monocot Agrostis stolonifera (bentgrass).

Secondary metabolites from Rubiaceae species

This study describes some characteristics of the Rubiaceae family pertaining to the occurrence and distribution of secondary metabolites in the main genera of this family. It reports the review of phytochemical studies addressing all species of Rubiaceae, published between 1990 and 2014. Iridoids, anthraquinones, triterpenes, indole alkaloids as well as other varying alkaloid subclasses, have shown to be the most common. These compounds have been mostly isolated from the genera Uncaria, Psychotria, Hedyotis, Ophiorrhiza and Morinda. The occurrence and distribution of iridoids, alkaloids and anthraquinones point out their chemotaxonomic correlation among tribes and subfamilies. From an evolutionary point of view, Rubioideae is the most ancient subfamily, followed by Ixoroideae and finally Cinchonoideae. The chemical biosynthetic pathway, which is not so specific in Rubioideae, can explain this and large amounts of both iridoids and indole alkaloids are produced. In Ixoroideae, the most active biosysthetic pathway is the one that produces iridoids; while in Cinchonoideae, it produces indole alkaloids together with other alkaloids. The chemical biosynthetic pathway now supports this botanical conclusion.

Iridoids as chemical markers of false ipecac (Ronabea emetica), a previously confused medicinal plant

ETHNOPHARMACOLOGICAL RELEVANCE

Several roots or rhizomes of rubiaceous species are reportedly used as the emetic and antiamoebic drug ipecac. True ipecac (Carapichea ipecacuanha) is chemically well characterized, in contrast to striated or false ipecac derived from the rhizomes of Ronabea emetica (syn. Psychotria emetica). Besides its previous use as substitute of ipecac, the latter species is applied in traditional medicine of Panama and fruits of its relative Ronabea latifolia are reported as curare additives from Colombia.

MATERIALS AND METHODS

Compounds of Ronabea emetica were isolated using standard chromatographic techniques, and structurally characterized by NMR spectroscopy and mass spectrometry. Organ specific distribution in Ronabea emetica as well as in Ronabea latifolia was further assessed by comparative HPLC analysis.

RESULTS

Four iridoid-glucosides, asperuloside (1), 6α-hydroxygeniposide (2), deacetylasperulosidic acid (3) and asperulosidic acid (4) were extracted from leaves of Ronabea emetica. Rhizomes, used in traditional medicine, were dominated by 3. HPLC profiles of Ronabea latifolia were largely corresponding. These results contrast to the general tendency of producing emetine-type and indole alkaloids in species of Psychotria and closely related genera and merit chemotaxonomic significance, characterizing the newly delimited genus Ronabea.

CONCLUSIONS

The aim of the work was to resolve the historic problem of adulteration of ipecac by establishing the chemical profile of Ronabea emetica, the false ipecac, as one of its less known sources. The paper demonstrates that different sources of ipecac can be distinguished by their phytochemistry, thus contributing to identifying adulterations of true ipecac.

Naturally occurring secoiridoids and bioactivity of naturally occurring iridoids and secoiridoids. A review, part 2

Naturally occurring new secoiridoids published during 1994-2005 are reviewed with available physical and spectral data: mp, [alpha](D), UV, IR, (1)H- and (13)C-NMR and plant source. The works on biological and pharmacological activity of naturally occurring iridoids and secoiridoids reported during 1998-2005 are also reviewed. Bioactivities like antiallergic, antiarthritis, antibacterial, anticancer, anticoagulant, anticomplement, antifungal, antiinflammatory, antioxidative, antiprotozoal, antispasmodic, antiviral, immunomodulatory, neuroprotective, nerve growth factor potentiating and wound healing activities are highlighted.

Naturally occurring iridoids. A review, part 1

A compilation of new naturally occurring iridoid glycosides, iridoid aglycones, iridoid derivatives and bis-iridoids reported during 1994-2005 is provided with available physical and spectral data: mp, [alpha]D, UV, IR, 1H- and 13C-NMR as well as natural source with family and references. 418 compounds with 202 references are cited.

Toxicological evaluation of an ethanolic extract from Chiococca alba roots

The roots of Chiococca alba have been employed to treat rheumatic disorders and for other therapeutic purposes in Brazil and elsewhere. This study was undertaken to evaluate the toxicological properties of an ethanolic extract from Chiococca alba roots (EE), including mutagenicity in the Salmonella assay and acute and subacute toxicity to mice. Single oral doses of EE caused hypoactivity, but no deaths were noted up to the highest dose tested (2000 mg/kg). EE (500 mg/kg p.o.) reduced mouse locomotion in the open field test. EE was markedly more toxic when given by intraperitoneal (i.p.) and subcutaneous (s.c.) routes. Acute approximate lethal doses (ALD) were 125 mg/kg (males) and 250 mg/kg (females) and 250 mg/kg (both sexes) by i.p. and s.c. routes, respectively. Deaths after single doses were preceded by hypoactivity, ataxia and lethargy. Repeated administration of EE by gavage for 14 days caused no deaths. Activity of liver monooxygenases (pentoxy- and ethoxyresorufin-O-dealkylases) was not altered by repeated treatment with EE (2000 mg/kg/day p.o.). Administration of EE by the i.p. route for 14 days decreased weight gain and caused anemia, neutrophilia and deaths. The no-observed-adverse-effect level (NOAEL) for subacute treatment by the i.p. route was as low as 15.6 mg of EE/kg body weight (wt)/day. EE was not mutagenic in the Salmonella/microsome assay with TA100, TA98, TA97a and TA1535 strains. In summary, EE was not mutagenic and presented a low acute and subacute toxicity by the oral route. Toxicities by parenteral routes, however, were more pronounced.

Inhibitory effect on TNF-alpha-induced IL-8 production in the HT29 cell of constituents from the leaf and stem of Weigela subsessilis

Twelve compounds were isolated from the MeOH extract of the leaf and stem of the Korean endemic plant Weigela subsessilis L. H. Bailey. Their chemical structures were elucidated on the basis of physicochemical and spectroscopic data and by comparison with those of published literatures. These compounds were identified as three sterols, beta-sitosterol acetate (2), betasitosterol (3), daucosterol (11), eight triterpenoids, squalene (1), ursolic acid (4), ilekudinol A (5), corosolic acid (6), ilekudinol B (7), esculentic acid (8), pomolic acid (9), asiatic acid (10), and one iridoid glycoside, alboside I (12). This is the first report pertaining to the isolation of these compounds from Weigela subsessilis L. H. Bailey. In addition, three compounds 7, 9, and 12 were found to display a strong inhibitory effect on the production of IL-8 in the HT29 cells stimulated by TNF-alpha.

seco-iridoids from Calycophyllum spruceanum (Rubiaceae)

Three seco-iridoids 7-methoxydiderroside, 6'-O-acetyldiderroside and 8-O-tigloyldiderroside, were isolated from the wood bark of Calycophyllum spruceanum together with the known iridoids loganetin, loganin and the seco-iridoids secoxyloganin, kingiside and diderroside. Their structures were elucidated by means of NMR and MS spectral data analysis. Using NOE correlations and coupling constants, the relative stereochemistry of the new derivatives was established. 7-Methoxydiderroside, 6'-O-acetyldiderroside and the known secoxyloganin and diderroside showed in vitro activity against trypomastigote forms of Trypanosoma cruzi, with IC(50) values of 59.0, 90.2, 74,2 and 84.9 microg/mL, respectively and were compared to the standard gentian violet (IC(50) 7.5 microg/ml).

Antifungal polysulphides from Petiveria alliacea L

Bioactivity-directed fractionation of the CH(2)Cl(2)/MeOH (2:1, v/v) extract of the roots of Petiveria alliacea, using mutant yeast strains of Saccharomyces cerevisiae and fungi Cladosporium cladosporioides and C. sphaerospermum led to the isolation of dipropyl disulphide (1), dibenzyl sulphide (2), dibenzyl disulphide (3), dibenzyl trisulphide (4), dibenzyl tetrasulphide (5), benzylhydroxymethyl sulphide (6) and di(benzyltrithio) methane (7). Of these, 5-7 are new compounds and this is the first report of the natural occurrence of 2 and 3.