Discovery and structure–activity relationships of ent-Kaurene diterpenoids as potent and selective 11β-HSD1 inhibitors: Potential impact in diabetes

New Brusatol Derivatives as Anti-Settlement Agents Against Barnacles, Targeting HSP90: Design, Synthesis, Biological Evaluation, and Molecular Docking Investigations

The increasing challenge of marine biofouling, mainly due to barnacle settlement, necessitates the development of effective antifoulants with minimal environmental toxicity. In this study, fifteen derivatives of brusatol were synthesized and characterized using 13C-NMR, 1H-NMR, and mass spectrometry. All the semi-synthesized compounds obtained using the Multi-Target-Directed Ligand (MTDL) strategy, when evaluated as anti-settlement agents against barnacles, showed promising activity. Compound 3 exhibited the highest anti-settlement capacity, with an EC50 value of 0.1475 μg/mL, an LC50/EC50 ratio of 42.2922 (>15 indicating low toxicity), and a resuscitation rate of 71.11%, while it showed no significant phenotypic differences in the zebrafish embryos after treatment for 48 h. The toxicity screening of zebrafish also demonstrated the low ecotoxicity of the selected compounds. Furthermore, homology modeling of the HSP90 structure was performed based on related protein sequences in barnacles. Subsequently, molecular docking studies were conducted on HSP90 using these newly synthesized derivatives. Molecular docking analyses showed that most activated derivatives displayed low binding energies with HSP90, aligning well with the biological results. They were found to interact with key residues in the binding site, specifically ARG243, TYR101, and LEU73. These computational findings are anticipated to aid in predicting the enzyme targets of the tested inhibitors and their potential interactions, thus facilitating the design of novel antifoulants in future research endeavors.

Development and structure-activity relationships of tanshinones as selective 11β-hydroxysteroid dehydrogenase 1 inhibitors

11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) represents a promising drug target for metabolic syndrome, including obesity and type 2 diabetes. Our initial screen of a collection of natural products from Danshen led to the identification of tanshinones as the potent and selective 11β-HSD1 inhibitors. To improve the druggability and explore the structure-activity relationships (SARs), more than 40 derivatives have been designed and synthesized using tanshinone IIA and cryptotanshinone as the starting materials. More than 10 derivatives exhibited potent in vitro 11β-HSD1 inhibitory activity and good selectivity over 11β-HSD2 across human and mouse species. Based on the biological results, SARs were further discussed, which was also partially rationalized by a molecular docking model of 1 bound to the 11β-HSD1. Remarkably, compounds 1, 17 and 30 significantly inhibited 11β-HSD1 in 3T3-L1 adipocyte and in livers of ob/ob mice, which merits further investigations as anti-diabetic agents. This study not only provides a series of novel selective 11β-HSD1 inhibitors with promising therapeutic potentials in metabolic syndromes, but also expands the boundaries of the chemical and biological spaces of tanshinones.

Developing an UPLC-MS/MS method to quantify maoecrystal A in rat plasma: Application to a pharmacokinetic study

Maoecrystal A (MC-A) is an ent-kaurane-type diterpene isolated from Rabdosia eriocalyx (Dunn) Hara. MC-A has been reported to show different types of pharmacological activities, including anticancer, anti-inflammatory and bacteriostatic functions. However, bioanalysis of MC-A has not been reported. The purpose of this study is to develop an UPLC-MS/MS method to quantify MC-A in plasma and determine its pharmacokinetic properties using an animal model. The separation was performed using a Waters HSS T3 column (50 mm × 2.1 mm, 1.8 μm, Waters Corp., Milford, MA, USA) with methanol and water containing 0.1% of formic acid as the mobile phases. The mass analysis was performed in a Waters Xevo TQ mass spectrometer using multiple reaction monitoring (MRM) in positive scan mode. Protein precipitation was used to extract the drug from rat plasma samples. The calibration curve is linear in the concentration range 0.49-2000.0 ng/mL. The extraction recovery and the matrix effect were 78.11 to 91.72% and 90.38 to 98.02%, respectively. The RSD of inter/intra-day precisions were <13.72% and the accuracy was >86.41%. Stability studies showed that MC-A was stable (RSD < 14.98%) at different conditions (i.e., short-term, long-term, bench, and three freeze-thaw cycles) in rat plasma. The method was successfully applied to a pharmacokinetic study using rats through oral and intravenous administration routes. The oral bioavailability of MC-A was only 2.9%. Further studies are needed to determine the absorption and metabolism in order to improve the oral bioavailability of MC-A.

Dihydrochalcones and Diterpenoids from Pteris ensiformis and Their Bioactivities

Two new dihydrochalcone enantiomers (+)-1 and (-)-1, along with eight known compounds 3-10, were obtained from Pteris ensiformis. The planar structures were determined on the basis of extensive 1D and 2DNMR and HRESIMS. The resolution of (+)-1 and (-)-1 was achieved by chiral HPLC analysis. The absolute configurations of (+)-1 and (-)-1 were established by the bulkiness rule using Rh₂(O₂CCF₃)₄-induced circular dichroism (ICD) method. Compounds (+)-1, (-)-1, 8, 9 and 10 exhibited the inhibitory assay of NO production in mouse macrophages stimulated by LPS, with IC₅₀ values of 2.0, 2.5, 8.0, 9.5 and 5.6 μM, respectively. Otherwise, compound 10 showed moderate cytotoxic activity against HCT-116, HepG-2 and BGC-823 cell lines with IC₅₀ values of 3.0, 10.5 and 6.3 μM, respectively.

Synthesis of selective 11β-HSD1 inhibitors based on dammarane scaffold

Inspired by natural 11β-HSD1 inhibitors hupehenols A - E, a ring-focused strategy was applied for the synthesis of 35 structurally diverse dammarane-type derivatives. These derivatives were effectively prepared from protopanaxadiol based on the modification of rings A and D. Among these compounds, ten were identified as selective 11β-HSD1 inhibitors (IC50 range: 101-1047 nM, SI range: 8-169) which exhibited inhibitory activities against human or mouse 11β-HSD1. Otherwise, we found 23a could selectively inhibit both human and mouse 11β-HSD1 with IC50 value of 994 and 213 nM (SI > 10 and > 47), respectively. Additionally, the molecular modelling results of 23a docking into the human and mouse 11β-HSD1 were in good agreement with the results from the enzyme inhibitory experiment. Moreover, valuable structural-activity relationship (SAR) information of dammarane-type 11β-HSD1 inhibitor was summarized.

Synthesis of hupehenols A, B, and E from protopanaxadiol

A unified semisynthesis approach from protopanaxadiol to hupehenols A, B, and E was described. The synthesis provided the primary SAR and the possibility of further medicinal development of hupehenols.

Hupehenols A-E, selective 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors from Viburnum hupehense

Five selective 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) competitive inhibitors, hupehenols A-E (1-5), were isolated from Viburnum hupehense. The structure elucidation indicated that compounds 1-5 are new 20,21,22,23,24,25,26,27-octanordammarane triterpenoids. Their structures were established on the basis of NMR spectroscopic and mass spectrometric analysis. Hupehenols A-E (1-5) showed inhibition against human 11β-HSD1, with hupehenols B (2) and E (5) having IC50 values of 15.3 and 34.0 nM, respectively. Moreover, hupehenols C (3) and D (4) are highly selective inhibitors of human 11β-HSD1 when compared to murine 11β-HSD1.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December 2013 is reviewed.