Autoxidation of 4-amorphen-11-ol and the biogenesis of nor- and seco-amorphane sesquiterpenes from fabiana imbricata

Enantiomeric Isopulegol as the Chiral Pool in the Total Synthesis of Bioactive Agents

Isopulegol, a pool of abundant chiral terpene, has long served as the starting material for the total synthesis of isopulegol-based drugs. As an inexpensive and versatile starting material, this compound continues to serve modern synthetic chemistry. This review highlights the total syntheses of terpenoids in the period from 1980 to 2020 in which with isopulegol applied as a building block.

Fabiana imbricata Ruiz et Pav. (Solanaceae), a review of an important Patagonian medicinal plant

ETHNOPHARMACOLOGICAL RELEVANCE

Fabiana imbricata (Solanaceae) is a Patagonian medicinal plant with a long tradition of use. The aim of this review is to provide an integrative overview of the traditional uses, chemistry, bioactivity and chemical profiling of the crude drug.

MATERIALS AND METHODS

The information was collected from scientific databases searching with the keywords Fabiana imbricata, Fabiana species, Fabiana (Solanaceae) and includes local literature and books.

RESULTS

The indications of use reported in literature show little variation from the data published as early as 1889. The chemical studies showed a rich diversity in metabolites including phenolics, coumarins, flavonoids, phenylpropanoids, terpenes, alkaloids and sugars. Bioactivity studies supported the traditional use as diuretic and also the potential of the crude drug as a gastroprotective agent. The plant can be used as a source of compounds with effect on gastric ulcers and shows enzyme inhibitory activity. While the germination rate of the plant is very low, protocols were developed for the rapid in vitro propagation of the species. The toxicity of the crude drug extracts was low and did not show clastogenic effect in human lymphocytes. Further research is needed to disclose the potential of the F. imbricata sesquiterpenes on other relevant biological targets.

Identification and characterization of a novel sesquiterpene synthase, 4-amorphen-11-ol synthase, from Artemisia maritima

Artemisinin, a sesquiterpene lactone exhibiting effective antimalarial activity, is produced by only Artemisia annua plant. A key step in artemisinin biosynthesis is the cyclization of farnesyl pyrophosphate (FPP) to amorpha-4,11-diene catalyzed by amorpha-4,11-diene synthase (AaADS). Intriguingly, several non-artemisinin-producing Artemisia plants also express genes highly homologous to AaADS. Our previous functional analysis of these homologous enzymes revealed that they catalyzed the synthesis of rare natural sesquiterpenoids. In this study, we analyzed the function of another putative sesquiterpene synthase highly homologous to AaADS from A. maritima. Unlike AaADS, in vivo enzymatic assay showed that this enzyme cyclized FPP to 4-amorphen-11-ol, a precursor of several gastroprotective agents. The discovery of 4-amorphen-11-ol synthase (AmAOS) and the successful de novo production of 4-amorphen-11-ol in engineered yeast demonstrated herein provides insights into the methods used to enhance its production for future application.

Stereocontrolled Synthesis of Kalihinol C

We report a concise chemical synthesis of kalihinol C via a possible biosynthetic intermediate, "protokalihinol", which was targeted as a scaffold en route to antiplasmodial analogs. High stereocontrol of the kalihinol framework relies on a heterodendralene cascade to establish the target stereotetrad. Common problems of regio- and chemoselectivity encountered in the kalihinol class are explained and solved.

Comparative study of antioxidant and anti-inflammatory activities and genotoxicity of alcoholic and aqueous extracts of four Fabiana species that grow in mountainous area of Argentina

ETHNOPHARMACOLOGICAL RELEVANCE

Fabiana species (Solanaceae family) extracts have long been used in Argentinean traditional medicine as anti-inflammatories, antiseptic, bone fractures and others diseases, but there is no scientific evidence which supports their use.

AIM OF THE STUDY

The present study was conducted to evaluate the ability of aqueous and ethanolic extracts of four Fabiana species (Fabiana bryoides Phil., Fabiana punensis A.C. Arroyo, Fabiana densa J. Rèmy and Fabiana patagonica Speg.) to inhibit key enzymes in inflammatory processes, free radical scavenging properties and genotoxic effects.

MATERIALS AND METHODS

HPLC-DAD of aqueous and ethanolic extracts from four Fabiana species was established. All Fabiana extracts were evaluated on their ability to inhibit hyaluronidase and lipoxygenase enzymes to assess their activity against inflammatory mediators. Antioxidant capacity was determined using the 2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assays and β-carotene-linolenic acid assay. Genotoxicity was evaluated by the Ames assay.

RESULTS

The results indicated that the chromatographic patterns of four Fabiana species were different in quantity and absorption intensity of peaks. The alcoholic extract of Fabiana punensis was the most active scavenger of DPPH and ABTS(+) radicals (SC(50) values of 3.85 ± 0.24 and 2.56 ± 0.10 μgGAE/mL, respectively). Fabiana patagonica extracts exhibited the highest peroxyl radical scavenging activity compared with the other three taxa (IC(50) values between 1.00 ± 0.04 and 4.46 ± 0.40 μg GAE/mL for all extracts) and anti-lipoxygenase activity with IC(50) values between 12.5 and 15.5 μg GAE/mL. The absence of mutagenicity indicates that the DNA does not seem to be a relevant target for these extracts. Fabiana bryoides ethanolic extract showed an interesting effect: it inhibited spontaneous mutagenesis, which could be considered as an antimutagenic effect in the TA98 (+S9) and TA100 (+S9/-S9) strains. The potency differences found between the species could be consequence of the different phytochemical pattern observed by HPLC.

CONCLUSIONS

The inhibitory effects on lipoxygenase and hyaluronidase, free radical scavenging activities and lack of genotoxicity of Fabiana extracts may support the folk use of Fabiana punensis, Fabiana patagonica, Fabiana bryoides and Fabiana densa as inhibitor of inflammatory mediators.

Cytotoxic norsesquiterpene peroxides from the endophytic fungus Talaromyces flavus isolated from the mangrove plant Sonneratia apetala

Four new norsesquiterpene peroxides, named talaperoxides A-D (1-4), as well as one known analogue, steperoxide B (5, or merulin A), have been isolated from a mangrove endophytic fungus, Talaromyces flavus. Their structures were elucidated mainly by 1D and 2D NMR. Structures of 1, 2, and 5 were further confirmed by single-crystal X-ray diffraction, and their absolute configurations were also determined using copper radiation. Cytotoxic activities of compounds 1-5 were evaluated in vitro against human cancer cell lines MCF-7, MDA-MB-435, HepG2, HeLa, and PC-3. Compounds 2 and 4 showed cytotoxicity against the five human cancer cell lines with IC50 values between 0.70 and 2.78 μg/mL.

Terpenoids from the seeds of Artemisia annua

Fourteen sesquiterpenes, three monoterpenes and one diterpene natural product have been isolated from the seeds of Artemisia annua. The possible biogenesis of some of these natural products are discussed by reference to recently reported experimental results for the autoxidation of dihydroartemisinic acid and other terpenoids from Artemisia annua.

Maculalactone M from the marine cyanobacterium Kyrtuthrix maculans

Maculalactone M, a seco-dibenzyldiphenyl-4,5,6,7-tetrahydrobenzofuranone, was isolated from the epilithic encrusting cyanobacterium Kyrtuthrix maculans. A possible biogenetic route to this compound is proposed involving cleavage of an allylic hydroperoxide.