Iridoids Isolation from a Phytochemical Study of the Medicinal Plant Teucrium parviflorum Collected in Iraqi Kurdistan

Herbal medicines are still widely practiced in Kurdistan Region-Iraq, especially by people living in villages on mountainous regions. Among plants belonging to the genus Teucrium (family Lamiaceae), which are commonly employed in the Kurdish traditional medicine, we have analyzed, for the first time, the methanol and aqueous methanol extracts of T. parviflorum aerial parts. The plant is mainly used by Kurds to treat jaundice, liver disorders and stomachache. We aimed to determine the phytochemical profile of the extracts and the structures of the main components, so to provide a scientific rationale for the ancient use of the plant in the ethno-pharmacological field. TLC analysis of the two extracts on silica gel and reversed phase TLC plates, using different visualization systems, indicated similar contents and the presence of phenolics, flavonoids, terpenoids and sugars. The chlorophyll-free extracts exhibited weak/no antimicrobial activities against a panel of bacteria (MICs = 800–1600 µg/mL) and fungal strains (MICs ≥ 5 mg/mL). At the concentration of 600 µg/mL, the methanol extract showed moderate antiproliferative effects against A549 and MCF-7 cancer cell lines in the MTS assay. Moreover, both extracts exhibited a significant dose-dependent free radical scavenging action against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC₅₀ = 62.11 and 44.25 μg/mL, respectively). In a phytochemical study, a high phenolic content (77.08 and 81.47 mg GAE/g dry extract, respectively) was found in both extracts by the Folin–Ciocalteu assay. Medium pressure liquid chromatographic (MPLC) separation of the methanol extract on a reversed phase cartridge eluted with a gradient of MeOH in H₂O, afforded two bioactive iridoid glucosides, harpagide (1) and 8-O-acetylharpagide (2). The structures of 1 and 2 were established by spectral data, chemical reactions, and comparison with the literature. Interestingly, significant amounts of hepatotoxic furano neo-clerodane diterpenoids, commonly occurring in Teucrium species, were not detected in the extract. The wide range of biological activities reported in the literature for compounds 1 and 2 and the significant antiradical effects of the extracts give scientific support to the traditional use in Iraqi Kurdistan of T. parviflorum aerial parts for the preparation of herbal remedies.

Fragmentation study of clerodane diterpenes from Casearia species by tandem mass spectrometry (quadrupole time-of-flight and ion trap)

RATIONALE

Clerodane-type diterpenes from Casearia species show important pharmacological activites such as antitumor, antimicrobial and anti-inflamatory. There are several mass spectrometry (MS)-based methods for identification of diterpenes; however, there is still a lack of MS procedures capable of providing characteristic fragmentation pathways for a rapid and unambiguous elucidation of casearin-like compounds.

METHODS

Casearin-like compounds were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation studies were carried out by tandem mass spectrometry in space (quadrupole time-of-flight (QTOF)) using different collision energies and also by tandem mass spectrometry in time (QIT) by selective isolation of product ions.

RESULTS

Casearin-like compounds presented a predominance of sodium- and potassium-cationized precursor ions. Both QIT and QTOF techniques provided sequential neutral losses of esters related to the R₁ to R₅ substituents linked to the nucleus of the clerodane diterpenes. The fragmentation pathway is initiated with a cleavage of the ester moieties R₂ followed by the elimination of the ester groups R₃ , both losing neutral carboxylic acids. Using QIT, it was also possible to observe the cleavage of the ester groups R₁ or R₅ by MS⁴ experiments.

CONCLUSIONS

Through a rational analysis of the fragmentation mechanisms of Casearia diterpenes it was possible to suggest an annotation strategy based on the sequential cleavages of the ester groups related to the R₂ , R₃ and R₅ substituents. These results will assist studies of the dereplication and metabolomics involving casearin-like compounds present in complex extracts of Casearia species.

Characterization of Casearin X Metabolism by Rat and Human Liver Microsomes

Casearin X (CAS X) is the major clerodane diterpene isolated from the leaves of Casearia sylvestris and has been extensively studied due to its powerful cytotoxic activity at low concentrations. Promising results for in vivo antitumor action have also been described when CAS X was administered intraperitoneally in mice. Conversely, loss of activity was observed when orally administered. Since the advancement of natural products as drug candidates requires satisfactory bioavailability for their pharmacological effect, this work aimed to characterize the CAS X metabolism by employing an in vitro microsomal model for the prediction of preclinical pharmacokinetic data. Rat and human liver microsomes were used to assess species differences. A high-performance liquid chromatography with diode-array detection (HPLC-DAD) method for the quantification of CAS X in microsomes was developed and validated according to European Medicines Agency guidelines. CAS X was demonstrated to be a substrate for carboxylesterases via hydrolysis reaction, with a Michaelis-Menten kinetic profile. The enzyme kinetic parameters were determined, and the intrinsic clearance was 1.7-fold higher in humans than in rats. The hepatic clearance was estimated by in vitro-in vivo extrapolation, resulting in more than 90% of the hepatic blood flow for both species. A qualitative study was also carried out for the metabolite identification by mass spectrometry and indicated the formation of the inactive metabolite CAS X dialdehyde. These findings demonstrate that CAS X is susceptible to first-pass metabolism and is a substrate for specific carboxylesterases expressed in liver, which may contribute to a reduction in antitumor activity when administered by the oral route.

Evaluation of the Intestinal Absorption Mechanism of Casearin X in Caco-2 Cells with Modified Carboxylesterase Activity

The clerodane diterpene casearin X (1), isolated from the leaves of Casearia sylvestris, is a potential new drug candidate due to its potent in vitro cytotoxic activity. In this work, the intestinal absorption mechanism of 1 was evaluated using Caco-2 cells with and without active carboxylesterases (CES). An LC-MS method was developed and validated for the quantification of 1. The estimation of permeability coefficients was possible only under CES-inhibited conditions in which 1 is able to cross the Caco-2 cell monolayer. The mechanism is probably by active transport, with no significant efflux, but with a high retention of the compound inside the cells. The enzymatic hydrolysis assay demonstrates the susceptibility of 1 to first-pass metabolism as substrate for specific CES expressed in human intestine.

Vegetative anatomy and micromorphology of Salvia divinorum (Lamiaceae) from Mexico, combined with chromatographic analysis of salvinorin A

Salvia divinorum--a species traditionally cultivated in Oaxaca, Mexico--possesses hallucinogenic properties. It is legally recognized as a controlled substance and prohibited in many countries. The proper identification of the plant, both in fresh and dried forms, is an important issue in crime-prevention campaigns. This paper provides a thorough anatomical description of leaves, petioles, and stems of S. divinorum. Detailed investigation of foliar trichomes was performed and illustrated. In addition, chromatographic analyses, including TLC and HPLC, were applied to fresh and dried plant material, together with the standard reference salvinorin A. A comprehensive identification method for S. divinorum based on a thorough anatomical examination is proposed, combined with chemical analysis for proper plant recognition.

Analysis of Salvinorin A in plants, water, and urine using solid-phase microextraction-comprehensive two-dimensional gas chromatography-time of flight mass spectrometry

Salvinorin A, a psychoactive hallucinogen, and related compounds, were analyzed in plants, water, and urine using liquid-liquid extraction (LLE), solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS). A semi-qualitative study of the extraction of Salvinorin A and analogs from Salvia divinorum plants by LLE showed ppb levels of Salvinorin A and several analogs in the leaves and stems of S. divinorum plants, much lower than expected. Quantitative analysis of Salvinorin A spiked into water and urine showed much better figures of merit for SPME than LLE, with limit of detection of about 5 ng/mL, linear range from 8 to 500 ng/mL and precision about ±10% for the SPME-based analyses using external standard quantitation. GC×GC-ToFMS was especially effective in separating the peaks of interest from matrix and chromatographic interferences.

Antisecretory actions of Baccharis trimera (Less.) DC aqueous extract and isolated compounds: analysis of underlying mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Baccharis trimera (Less.) DC. (Asteraceae) is a species native to South America used in Brazilian folk medicine to treat gastrointestinal and liver diseases, kidney disorders and diabetes. Previous studies from this laboratory confirmed the antacid and antiulcer activities of the plant aqueous extract (AE) in rat and mouse models.

AIM OF THE STUDY

To investigate the mechanisms involved in the antacid action of AE and isolated compounds from Baccharis trimera.

MATERIALS AND METHODS

AE was assayed in vivo in cold-restraint stress gastric ulcers and in pylorus-ligated mice. Nine fractions (F2-F10) previously isolated from AE were assayed in vitro on acid secretion measured as [(14)C]-aminopyrine ([(14)C]-AP) accumulation in rabbit gastric glands, and on gastric microsomal H(+), K(+)-ATPase preparations. Chlorogenic acids (F2, F3, F6, F7), flavonoids (F9), an ent-clerodane diterpene (F8) and a dilactonic neo-clerodane diterpene (F10) have been identified in these fractions.

RESULTS

Intraduodenal injection of AE (1.0 and 2.0 g/kg) in 4h pylorus-ligated mice decreased the volume (20 and 50%) and total acidity (34 and 50%) of acid secretion compared to control values. Administered orally at the same doses AE protected against gastric mucosal lesions induced in mice by restraint at 4°C. Exposure of isolated rabbit gastric glands to fractions F8 (10-100 μM) and F9 (10-300 μg/ml) decreased the basal [(14)C]-AP uptake by 50 and 60% of control (Ratio=6.2±1.1), whereas the remaining fractions were inactive. In the presence of the secretagogues F2 and F4 (30-300 μg/ml) decreased the [(14)C]-AP uptake induced by histamine (His) with a 100-fold lower potency than that of ranitidine. F5 and F6 reduced the [(14)C]-AP uptake stimulated by carbachol (CCh), but they were 10 to 20-fold less potent than atropine. F8 (diterpene 2) and F9 (flavonoids) decreased both the His- and CCh-induced [(14)C]-AP uptake, whereas F10 (diterpene 1) was inactive against the [(14)C]-AP uptake stimulated by secretagogues. Diterpene 2 was the most active of all tested compounds being 7-fold less potent than ranitidine and equipotent to atropine in reducing acid secretion in vitro. This compound also reduced the gastric H(+), K(+)-ATPase activity by 20% of control, while the remaining fractions were inactive on the proton pump in vitro.

CONCLUSIONS

The results indicate that Baccharis trimera presents constituents that inhibit gastric acid secretion by acting mainly on the cholinergic regulatory pathway. The plant extract also contains compounds that exert moderate inhibition of the histaminergic regulatory pathway of acid secretion and the gastric proton pump. Altogether these active constituents appear to provide effective inhibition of acid secretion in vivo, which may explain the reputed antiulcer activity of the plant extract.

Direct analysis of Salvia divinorum leaves for salvinorin A by thin layer chromatography and desorption electrospray ionization multi-stage tandem mass spectrometry

Salvia divinorum is widely cultivated in the US, Mexico, Central and South America and Europe and is consumed for its ability to produce hallucinogenic effects similar to those of other scheduled hallucinogenic drugs, such as LSD. Salvinorin A (SA), a kappa opiod receptor agonist and psychoactive constituent, is found primarily in the leaves and to a lesser extent in the stems of the plant. Herein, the analysis of intact S. divinorum leaves for SA and of acetone extracts separated using thin layer chromatography (TLC) is demonstrated using desorption electrospray ionization (DESI) mass spectrometry. The detection of SA using DESI in the positive ion mode is characterized by several ions associated with the compound - [M+H](+), [M+NH(4)](+), [M+Na](+), [2M+NH(4)](+), and [2M+Na](+). Confirmation of the identity of these ions is provided through exact mass measurements using a time-of-flight (ToF) mass spectrometer. The presence of SA in the leaves was confirmed by multi-stage tandem mass spectrometry (MS(n)) of the [M+H](+) ion using a linear ion trap mass spectrometer. Direct analysis of the leaves revealed several species of salvinorin in addition to SA as confirmed by MS(n), including salvinorin B, C, D/E, and divinatorin B. Further, the results from DESI imaging of a TLC separation of a commercial leaf extract and an acetone extract of S. divinorum leaves were in concordance with the TLC/DESI-MS results of an authentic salvinorin A standard. The present study provides an example of both the direct analysis of intact plant materials for screening illicit substances and the coupling of TLC and DESI-MS as a simple method for the examination of natural products.

Antimicrobial evaluation of clerodane diterpenes from Polyalthia longifolia var. pendula

Phytochemical investigation of the ethanolic extract of leaves of Polyalthia longifolia var. pendula has led to the isolation of seven clerodane diterpenoids and five alkaloids. (-)-14, 15-bisnor-3, 11E-kolavadien-13-one (1), (-)-16-oxocleroda-3,13(14)E-dien-15-oic acid (2), (-)-16alpha-hydroxycleroda-3,13 (14)Z-dien-15,16-olide (3), (+)-(4-->2)-abeo-16(R/S)-2, 13Z-kolavadien-15, 16-olide-3-al (4), (-)-3beta, 16beta-dihydroxycleroda-4(18), 13(14)Z-dien-15,16-olide (5), (-)-3, 12E-kolavadien-15-oic acid-16-al (6), (-)-labd-13E-en-8-ol-15-oic acid (7), liriodenine (8), (-)-anonaine (9), (+)-isoboldine (10), (-)-asimilobine (11) and hordenine (12) have been isolated. This is the first report of 1, 6 and 10 from this plant species while 12 is reported for first time from this genus. Clerodane derivatives 1-7 were evaluated for their antimicrobial activity. Diterpene 3 was found to be most potent agent with MIC value of 6.25 microg/mL against Staphylococcus aureus and Sporothrix schenckii.

12-Acetoxyhawtriwaic acid lactone, a diterpene from Egletes viscosa, attenuates capsaicin-induced ear edema and hindpaw nociception in mice: possible mechanisms

The diterpene, 12-acetoxyhawtriwaic acid lactone (AHAL, tanabalin) isolated from the flower buds of Egletes viscosa Less. (Asteraceae) was evaluated on capsaicin-induced ear edema and hindpaw nociception in mice. AHAL (12.5, 25 and 50 mg/kg, P. O.) significantly attenuated the ear edema response to topically applied capsaicin (250 microg), in a dose-related manner. At similar doses, AHAL also suppressed the nocifensive paw-licking behavior induced by intraplantar injection of capsaicin (1.6 microg). These responses to capsaicin were also greatly inhibited by ruthenium red (3 mg/kg, S. C.), a non-competitive capsaicin receptor (TRPV1) antagonist. The anti-edema effect of AHAL (50 mg/kg) seems unrelated to either blockade of mast cell degranulation or to histamine and serotonin receptor antagonism since AHAL did not modify the paw edema response induced by intraplantar injections of compound 48/80, histamine or serotonin. However, the hindpaw edema induced by substance P and vascular permeability increase induced by intraperitoneal acetic acid were significantly suppressed by AHAL. The antinociceptive effect of AHAL (50 mg/kg) was unaffected by naloxone pretreatment but was significantly antagonized by theophylline and glibenclamide, the respective blockers of adenosine and K(ATP)-channels. AHAL (50 mg/kg, P. O.) did not impair the ambulation or motor coordination of mice in open-field and rota-rod tests. These data suggest that AHAL inhibits acute neurogenic inflammation possibly involving capsaicin-sensitive TRPV1-receptors, endogenous adenosine and ATP-sensitive potassium channels.

Determination of salvinorins and divinatorins in Salvia divinorum leaves by liquid chromatography/multistage mass spectrometry

Salvinorin A is the most potent naturally occurring hallucinogen known and rivals synthetic LSD in potency. Structurally it belongs to the neoclerodane diterpenoids, and it is the only known non-nitrogenous kappa-opioid-selective agonist. Salvia divinorum (Diviner's sage) is a member of the mint family that was used in ancient Mexican traditional practices. Today it is widely cultivated in Europe as a recreational marijuana substitute; it is illegal to buy, sell or possess the plant or the active principle in some countries. Six different salvinorins and three divinatorins have been isolated from Salvia divinorum leaves. The ion fragmentation, separation and quantitation of these diterpenes by liquid chromatography/electrospray ionization multistage mass spectrometry (LC/ESI-MS(n)) are described. The importance of LC in herbal extract determination and the chemical diagnostic power of MS(n) in the analysis of classes of natural organic products are discussed.