A pair of unprecedented cyclohexylethanoid enantiomers containing unusual trioxabicyclo[4.2.1]nonane ring from Clerodendrum bungei

Oxidative (3+3) Cycloaddition/Ring-Opening Reactions of Simple Urea Derivatives and N,N'-Cyclic Azomethine Imines to Construct 1,2,3,5-Tetrazine-4(1H)-one Derivatives

A novel oxidative (3 + 3) cycloaddition/ring-opening reaction of N,N'-cyclic azomethine imines with the in situ generated diaza-oxylallyl cations from simple urea derivatives in the presence of base and PhI(OAc)₂ has been developed. This transformation performs well over a broad substrate scope, which provides facile and rapid access to 1,2,3,5-tetrazine-4(1H)-one derivatives in good yields.

Traditional uses and pharmacological properties of Clerodendrum phytochemicals

Clerodendrum is a genus of ca. 500 species in the family Lamiaceae and widely distributed throughout the whole world. Up to now, many species of this genus have been described in various indigenous systems of medicine and are used in preparation of folklore medicines for the treatment of various life-threatening diseases, and more than eleven species of the Clerodendrum genus have been very well studied for their chemical constituents and biological activities, and 283 compounds, including monoterpene and its derivatives, sesquiterpene, diterpenoids, triterpenoids, flavonoid and flavonoid glycosides, phenylethanoid glycosides, steroids and steroid glycosides, cyclohexylethanoids, anthraquinones, cyanogenic glycosides, and others have been isolated and identified. Pharmacological studies have shown that these compounds and extracts from the Clerodendrum genus have extensive activities, such as anti-inflammatory and anti-nociceptive, anti-oxidant, anti-hypertensive, anticancer, antimicrobial, anti-diarrheal, hepatoprotective, hypoglycemic and hypolipidemic, memory enhancing and neuroprotective, and other activities. In this review, we attempt to highlight over phytochemical progress and list the phytoconstituents isolated from the genus Clerodendrum reported so far. The biological activities of this genus are also covered.

(±)-Ganoapplanin, a Pair of Polycyclic Meroterpenoid Enantiomers from Ganoderma applanatum

(±)-Ganoapplanin (1), a pair of novel meroterpenoid enantiomers featuring an unprecedented dioxaspirocyclic skeleton constructed from a 6/6/6/6 tetracyclic system and an unusual tricyclo[4.3.3.0^3',7']dodecane motif, were isolated from Ganoderma applanatum. Its structure and absolute configurations were determined by spectroscopic analyses, X-ray crystallography, and ECD (electronic circular dichroism calculations). A plausible biogenetic pathway, involving a key Gomberg-Bachmann reaction, was also proposed for (±)-1. Biological studies showed that (±)-1 and its enantiomers exhibited different inhibitory activities on T-type voltage-gated calcium channels.

Involucratusins A-H: Unusual Cadinane Dimers from Stahlianthus involucratus with Multidrug Resistance Reversal Activity

Three novel cadinane dimers, involucratusins A–C (1–3), five unique nor-cadinane-dimers, involucratusins D–H (4–8), together with a known compound (9) were isolated from the rhizomes of Stahlianthus involucratus. Their challenging structures and absolute configurations were determined by spectroscopic data, CD experimentation, chemical conversions and single-crystal X-ray diffraction. Compounds 1–3 are unusual cadinane dimers with new connection and novel cores. Compound 4 is a unique nor-cadinane-dimer, and 5 and 6 are two pairs of hemiketal racemates with novel dinor-cadinane-dimer backbone. Compounds 7 and 8 represent unusual dodecanor-cadinane-dimer and tetradecanor-cadinane-dimer carbon skeletons, respectively. The possible biogenetic pathways of 1–8 were proposed, involving nucleophilic addition, S_N2 nucleophilic displacement, [3 + 3] benzannulation, oxidative cleavage, decarboxylation, and oxidative phenol coupling reactions. Multidrug resistance (MDR) reversal activity assay of the isolates were evaluated in doxorubicin-resistant human breast cancer cells (MCF-7/DOX). The combined use of these novel cadinane dimers at a concentration of 10 μM increased the cytotoxicity of doxorubicin by 2.2–5.8-fold. It is the first report about the MDR reversal activity of cadinane dimers.

Antioxidant Lignans and Neolignans from Acorus tatarinowii

Eleven new lignans and neolignans, named acortatarinowins G-N (1-8), including three pairs of enantiomers (1a/1b-3a/3b) and five optically pure lignans and neolignans (4-8), along with five known analogs (9-14), were isolated from the rhizomes of Acorus tatarinowii Schott. Compounds 1-3 were successfully separated by chiral HPLC to afford 1a/1b-3a/3b. The planar structures of 1-8 were elucidated by extensive spectroscopic analyses including HRESIMS and NMR. Their absolute configurations were determined by analyses of single-crystal X-ray diffraction and a modified Mosher's method, assisted by experimental and calculated electronic circular dichroism (ECD) data. Compounds 1a and 1b were rare 7,8'-epoxy-8,7'-oxyneolignane. Compounds 1-8 were evaluated for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) reducing antioxidant power assay. Compound 6, exhibiting strong DPPH radical scavenging capacity with IC50 value of 16.4 ± 0.22 μg/mL, could interpret the herbal traditional usage.

(±)-Acortatarinowins A-F, Norlignan, Neolignan, and Lignan Enantiomers from Acorus tatarinowii

Three pairs of new 8-O-4'-type dinorneolignan enantiomers, (±)-acortatarinowins A-C (1a/1b-3a/3b), a pair of new 8-O-4'-type (4a/4b) and a pair of rare C7-C8'-type (5a/5b) neolignan enantiomers, (±)-acortatarinowins D and E, and a pair of new furofuran-type lignan enantiomers, (±)-acortatarinowin F (6a/6b), along with two pairs of known lignan enantiomers (7a/7b and 8a/8b), were obtained from the rhizomes of Acorus tatarinowii. The separation of 1-8 by chiral HPLC using a Daicel IC column led to the isolation of eight pairs of enantiomers, 1a/1b-8a/8b, which had variable enantiomeric excess (ee) values of approximately 66, 71, 63, 60, 0, 38, 48, and 75%, respectively. The structures were elucidated by extensive spectroscopic and chemical methods, and their absolute configurations were determined by a combined analysis of single-crystal X-ray diffraction and a modified Mosher's method, assisted by experimental and calculated electronic circular dichroism data. Among them, compounds 1a, 3a, 6b, 8a, and 8b showed weak inhibitory activities against NO production in activated macrophages with IC50 values ranging from 23.3 to 38.0 μM, respectively.

Sterols from Hericium erinaceum and their inhibition of TNF-α and NO production in lipopolysaccharide-induced RAW 264.7 cells

Erinarols G-J and 10 known ergostane-type sterols were isolated from a methanol extract of the dried fruiting bodies of Hericium erinaceum. Their chemical structures were elucidated using extensive spectroscopic analyses including 1D and 2D NMR experiments and HR-ESI-MS analysis, as well as through comparison with previously reported data. Anti-inflammatory effects of the isolated compounds were evaluated in terms of inhibition of tumor necrosis factor α (TNF-α) and nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophage cells. The results showed that erinarols H and J, as well as 2 of the ergostane-type sterols exhibited inhibitory activity against TNF-α secretion, with inhibition values ranging from 33.7% to 43.3% at 10 μM. Erinarols J and three ergostane-type sterols exhibited significant inhibitory effects against NO production, with inhibition values ranging from 38.4% to 71.5% at 10 μM.