The genomes of medicinal skullcaps reveal the polyphyletic origins of clerodane diterpene biosynthesis in the family Lamiaceae.

The presence of anticancer clerodane diterpenoids is a chemotaxonomic marker for the traditional Chinese medicinal plant Scutellaria barbata, although the molecular mechanisms behind clerodane biosynthesis are unknown. Here, we report a high-quality assembly of the 414.98 Mb genome of S. barbata into 13 pseudochromosomes. Using phylogenomic and biochemical data, we mapped the plastidial metabolism of kaurene (gibberellins), abietane, and clerodane diterpenes in three species of the family Lamiaceae (Scutellaria barbata, Scutellaria baicalensis, and Salvia splendens), facilitating the identification of genes involved in the biosynthesis of the clerodanes, kolavenol, and isokolavenol. We show that clerodane biosynthesis evolved through recruitment and neofunctionalization of genes from gibberellin and abietane metabolism. Despite the assumed monophyletic origin of clerodane biosynthesis, which is widespread in species of the Lamiaceae, our data show distinct evolutionary lineages and suggest polyphyletic origins of clerodane biosynthesis in the family Lamiaceae. Our study not only provides significant insights into the evolution of clerodane biosynthetic pathways in the mint family, Lamiaceae, but also will facilitate the production of anticancer clerodanes through future metabolic engineering efforts.

Hepatotoxicity in Cattle Associated with Salvia reflexa Diterpenes, including 7-Hydroxyrhyacophiline, a New Seco-Clerodane Diterpene.

A case of baled alfalfa hay contaminated with multiple weeds induced hepatotoxicity and death in cattle. The hepatotoxic compounds were isolated by bioassay-guided fractionation using a mouse model and identified as salviarin, salvianduline D, rhyacophiline, and 7-hydroxyrhyacophiline. The structure of 7-hydroxyrhyacophiline has not been previously reported. All compounds were found to induce severe acute hepatic necrosis within 24-48 h after a single oral dosage (260-280 mg/kg). The identified diterpenes are known to be found among different Salvia species which led to finding dried plant parts of Salvia reflexa within bales of weedy hay and subsequently a population of S. reflexa was found along the field edges and irrigation ditch banks of the alfalfa hay field. It was thus determined that S. reflexa was responsible for the hepatotoxicity observed in cattle fed the contaminated hay.

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.

In vitro metabolism of the anti-inflammatory clerodane diterpenoid polyandric acid A and its hydrolysis product by human liver microsomes and recombinant cytochrome P450 and UDP-glucuronosyltransferase enzymes.

1. The metabolism of the anti-inflammatory diterpenoid polyandric acid A (PAA), a constituent of the Australian Aboriginal medicinal plant Dodonaea polyandra, and its de-esterified alcohol metabolite, hydrolysed polyandric acid A (PAAH) was studied in vitro using human liver microsomes (HLM) and recombinant UDP-glucuronosyltransferase (UGT) and cytochrome P450 (CYP) enzymes. 2. Hydrolysis of PAA to yield PAAH occurred upon incubation with HLM. Further incubations of PAAH with HLM in the presence of UGT and CYP cofactors resulted in significant depletion, with UGT-mediated depletion as the major pathway. 3. Reaction phenotyping utilising selective enzyme inhibitors and recombinant human UGT and CYP enzymes revealed UGT2B7 and UGT1A1, and CYP2C9 and CYP3A4 as the major enzymes involved in the metabolism of PAAH. 4. Analysis of incubations of PAAH with UDP-glucuronic acid-supplemented HLM and recombinant enzymes by UPLC/MS/MS identified three glucuronide metabolites. The metabolites were further characterised by ß-glucuronidase and mild alkaline hydrolysis. The acyl glucuronide of PAAH was shown to be the major metabolite. 5. This study demonstrates the in vitro metabolism of PAA and PAAH and represents the first systematic study of the metabolism of an active constituent of an Australian Aboriginal medicinal plant.

Stereo and regioselective microbial reduction of the clerodane diterpene 3,12-dioxo-15,16-epoxy-4-hydroxycleroda-13(16),14-diene.

The biotransformation of the clerodane diterpene, 3,12-dioxo-15,16-epoxy-4-hydroxy-cleroda-13(16),14-diene (1), obtained from Croton micans var. argyroglossum (Baill.) Mill., was investigated for the first time. Whole cells of Cunninghamella echinulata and Rhizopus stolonifer were used as enzymatic systems, and with both fungi the only biotransformation product obtained was the new ent-neo-clerodane diterpene (3R,4S,5S,8S,9R,10S)-3,4-dihydroxy-15,16-epoxy-12-oxo-cleroda-13(16),14-diene (2a). The absolute stereochemistry of 2a was inferred by comparison of its optical rotation with those of the chemical reduction product of 1 and its quasienantiomer 2c.

Salvinorin A analogs and other κ-opioid receptor compounds as treatments for cocaine abuse.

Acute activation of kappa-opioid receptors produces anti-addictive effects by regulating dopamine levels in the brain. Unfortunately, classic kappa-opioid agonists have undesired side effects such as sedation, aversion, and depression, which restrict their clinical use. Salvinorin A (Sal A), a novel kappa-opioid receptor agonist extracted from the plant Salvia divinorum, has been identified as a potential therapy for drug abuse and addiction. Here, we review the preclinical effects of Sal A in comparison with traditional kappa-opioid agonists and several new analogs. Sal A retains the anti-addictive properties of traditional kappa-opioid receptor agonists with several improvements including reduced side effects. However, the rapid metabolism of Sal A makes it undesirable for clinical development. In an effort to improve the pharmacokinetics and tolerability of this compound, kappa-opioid receptor agonists based on the structure of Sal A have been synthesized. While work in this field is still in progress, several analogs with improved pharmacokinetic profiles have been shown to have anti-addictive effects. While in its infancy, it is clear that these compounds hold promise for the future development of anti-addictive therapeutics.

[Salvinorin A and related diterpenes--biological activity and potential therapeutic uses]. / Salwinoryna A i jej pochodne--aktywnosc biologiczna i potencjalne zastosowanie terapeutyczne.

Salvinorin A (SA) is the main active ingredient of Salvia divinorum, a naturally occurring hallucinogen plant from Mexico. Traditionally, herbal preparations obtained from Salvia were used by the Mazatec Indians for their divination rites and the treatment of gastrointestinal disorders. SA is a selective K-opioid receptor agonist, producing antinociception in animals and humans and displaying regulatory effect on colonic function. Studies in humans demonstrated potent hallucinogenic effect of SA. The extensive research on SA and related neoclerodane diterpenes over the past few years resulted in a number of reports on their isolation, synthesis, and pharmacological characterization. In this review we try to summarize, from the pharmacological and synthetic point of view, the structure-activity relationship studies of SA and discuss the possible use of SA and its derivatives as therapeutics.

Synthesis and biological evaluation of C-12 triazole and oxadiazole analogs of salvinorin A.

Salvinorin A (1), the main active ingredient of Salvia divinorum, is a potent and selective kappa-opioid receptor (KOPR) agonist. A series of C-12 triazole analogs and the oxadiazole (4) analog of 1 are synthesized and screened for binding affinity at kappa, mu (MOPR), or delta (DOPR). Surprisingly, all triazole analogs have shown negligible binding affinity at opioid receptors and the oxadiazole 4, a reported MOPR and KOPR antagonist, exhibits very low affinities to opioid receptors and no antagonism in our binding assays. These results suggest that electronic factors that may affect either the electron density of hydrogen bond acceptor at C-12 or hydrophobic interactions between C-12 moiety and KOPR are critical to C-12 analog's affinity for KOPR.

Four new neo-clerodane diterpenoid alkaloids from Scutellaria barbata with cytotoxic activities.

Four new neo-clerodane diterpenoid alkaloids, named scutebarbatines C-F (1-4), were isolated from the whole plants of Scutellaria barbata D. DON. Their structures were elucidated by spectral analyses (UV, IR, FAB-MS, 1D-NMR and 2D-NMR). In vitro, compounds 1-4 showed significant cytotoxic activities against three human cancer cell lines, namely, HONE-1 nasopharyngeal, KB oral epidermoid carcinoma, and HT29 colorectal carcinoma cells, and gave IC(50) values in the range 3.9-7.8 muM.