Icetexane diterpenoids as Cav3.2 T-type calcium channel inhibitors from Salvia prattii and analgesic effect of their Semi-synthesized derivatives.

Ten new icetexane diterpenoids, salpratins E-N (1-10) and a known analogue (11) were characterized from Salvia prattii Hemsl. Structurally, 1 is the first 19(4 â†’ 3)-abeo-icetexane diterpenoid featuring with a 6/7/6 ring system. The structures of isolated compounds were determined by comprehensive analyses of spectroscopic data, ECD calculation, and single-crystal X-ray diffraction. Biological studies initially revealed that 1, 7, 10, and 11 are notable Cav3.2 T-type Ca2+ channel (TTCC) inhibitors with IC50 values of 2.9, 5.1, 2.3, and 3.2 µM, respectively. Five icetexane related derivatives (13-17) were synthesized from an abietane type precursor, (+)-carnosic acid (12), for the purpose of overcoming the poor water solubility of aforementioned active compounds and further investigating diverse diterpenes with valuable activity. Among them, 13 and 14 showed potent inhibitions on Cav3.2, having IC50 values of 6.7 and 2.4 µM, respectively. Significantly, they exhibited dose-dependent (1, 3, and 10 mg/kg) and comparable analgesic effects as that of Z944, a TTCCs inhibitor under clinical trial for pain management, in the mouse acetic acid writhing test. These findings further enrich structural diversity and bioactivity of Salvia diterpenoids, as well as provide promising structural templates for the development of Cav3.2 analgesics.

Discovery of novel coffee diterpenoids with inhibitions on Cav3.1 low voltage-gated Ca2+ channel.

Seven new (1-4, 6-8) diterpenoids with rare skeletons and seven known ones (9, 12, 17, 18 and 23-25) were isolated from roasted beans of Coffea arabica L. Together with previously obtained diterpenoids, a total of 26 molecules (1-25, 4a) were evaluated their activities on Cav3.1 low voltage-gated Ca2+ channel. Compounds 1, 3, 6, 7, 12, 13, 17, 19 and 24 exhibited noticeable Cav3.1 inhibitions (41.2%-96.1%) at 10 µM. The IC50 values of 1, 6, 7, 12, 13, 17 and 24 are 2.9, 2.3, 0.68, 14.8, 11.6, 6.1 and 6.8 µM, respectively. The ring moiety at C-18 and C-19, and esterification of OH-17 with long-chain fatty acids seem important for their activities. Further studies indicated that 1 and cafestol may act on different binding sits with the Cav3.1 blocker Z944, which is in clinical trial. Significantly, the present study initially shows that coffee diterpenoids are potential natural resources for Cav3.1 inhibitors.

Novel Meroterpenoids from Hypericum patulum: Highly Potent Late Nav1.5 Sodium Current Inhibitors.

Hypulatones A and B (1 and 2), two racemic meroterpenoids possessing an unprecedented spiro[benzofuran-2,1'-cycloundecan]-4'-ene-4,6(5H)-dione core, were characterized from Hypericum patulum. Compound 2 was found to significantly inhibit the late current of Nav1.5 (late INa, IC50 = 0.2 µM). Importantly, 2 exhibited remarkable separation (>100-fold) of late INa relative to peak INa and notable selectivity over Cav3.1, Kv1.5, and hERG. 1 showed comparable inhibition on late INa compared to that of 2 with poorer selectivity.

Congenetic Hybrids Derived from Dearomatized Isoprenylated Acylphloroglucinol with Opposite Effects on Cav3.1 Low Voltage-Gated Ca2+ Channel.

A hybrid of dearomatized isoprenylated acylphloroglucinol (DIAP) and monoterpenoid, hypatone A (1), together with its biosynthetic analogues 2-4 is characterized from Hypericum patulum. Structurally, 1 possesses an unprecedented spiro[bicyclo[3.2.1]octane-6,1'-cyclohexan]-2',4',6'-trione core as elucidated by extensive spectroscopic and X-ray crystallographic analyses. Biological studies reveal that compounds 1 and 2-4 produce opposite effects on Cav3.1 low voltage-gated Ca2+ channel, with 1 and 4, respectively, being the most potent Cav3.1 agonist and antagonist from natural products. Further studies suggest that compound 1 and its biogenetical precursor, 2, have the same binding site on Cav3.1 and that the rigid cagelike moiety at C-5 and C-6 is a key structural feature responsible for 1 being an agonist. Furthermore, 1 can normalize the pathological gating of a mutant Cav3.1 channel found in spinocerebellar ataxia 42 (SCA42), a hereditary neurodegenerative disorder with no available therapy. Collectively, our findings provide valuable tools for future studies on Cav3.1 physiology and pathophysiology, as well as afford possible leads for developing new drugs against SCA42, epilepsy, and pain.