2-Oxabicyclo[2.1.1]hexanes as saturated bioisosteres of the ortho-substituted phenyl ring.

The ortho-substituted phenyl ring is a basic structural element in chemistry. It is found in more than three hundred drugs and agrochemicals. During the past decade, scientists have tried to replace the phenyl ring in bioactive compounds with saturated bioisosteres to obtain novel patentable structures. However, most of the research in this area has been devoted to the replacement of the para-substituted phenyl ring. Here we have developed saturated bioisosteres of the ortho-substituted phenyl ring with improved physicochemical properties: 2-oxabicyclo[2.1.1]hexanes. Crystallographic analysis revealed that these structures and the ortho-substituted phenyl ring indeed have similar geometric properties. Replacement of the phenyl ring in marketed agrochemicals fluxapyroxad (BASF) and boscalid (BASF) with 2-oxabicyclo[2.1.1]hexanes dramatically improved their water solubility, reduced lipophilicity and most importantly retained bioactivity. This work suggests an opportunity for chemists to replace the ortho-substituted phenyl ring in bioactive compounds with saturated bioisosteres in medicinal chemistry and agrochemistry.

1,2-Disubstituted bicyclo[2.1.1]hexanes as saturated bioisosteres of ortho-substituted benzene.

Bicyclo[2.1.1]hexanes have been synthesized, characterized, and biologically validated as saturated bioisosteres of the ortho-substituted benzene ring. The incorporation of the 1,2-disubstituted bicyclo[2.1.1]hexane core into the structure of fungicides boscalid (BASF), bixafen (Bayer CS), and fluxapyroxad (BASF) gave saturated patent-free analogs with high antifungal activity.

Effect of Cytokinin-Containing Extracts from Some Medicinal Mushroom Mycelia on HepG2 Cells In Vitro.

Endogenous cytokinins in mycelia of medicinal mushrooms Hericium coralloides and Fomitopsis officinalis grown in vitro were identified using high-performance liquid chromatography coupled with mass spectrometry. High amounts of zeatin-type cytokinins and isopentenyladenine were found. The qualitative composition and quantitative content of cytokinins were species-specific traits of mushrooms. Optical microscopy was used to perform a comparison analysis of the influence of crude extracts and purified cytokinin fractions from both species' mycelial biomass on HepG2 tumor cell growth in vitro and morphology. The results showed that purified cytokinin fractions from H. coralloides and F. officinalis mycelia demonstrated a cytotoxic effect on HepG2 cells, unlike crude extracts. Under the influence of all mushroom extracts, similar patterns of changes in HepG2 cell morphology were observed, but they were more pronounced for H. coralloides compared with F. officinalis. Purified fractions of both mushroom species caused an increased level of apoptosis compared to crude extracts. Some increase in glucose uptake by cultured cells was found in all investigated samples wherein the influence of H. coralloides extracts was approximately twice the effect of the corresponding F. officinalis extracts. The data obtained confirm the assumption that cytokinins are involved in the expression of therapeutic effects of medicinal mushrooms and indicate the need to take into consideration the methods of cytokinin extraction when preparing pharmacologically active drugs based on fungal raw materials. Thus, extracts from H. coralloides and F. officinalis mycelial biomass are promising in the search for anticancer agents.

Comparative Analysis of Cytokinins in Mycelial Biomass of Medicinal Mushrooms.

Mushrooms are known to produce phytohormones, in particular cytokinins. Here we studied in vitro production of cytokinins in medicinal mushrooms. Cytokinins were identified and quantified in mycelial biomass of 13 species by using high-performance liquid chromatography-mass spectrometry. Trans-zeatin, zeatin riboside, zeatin-O-glucoside, isopentenyladenosine, and isopentenyladenine were found but only 1 species (Ganoderma lucidum) contained all these forms. Zeatin-type cytokinins predominated. Composition of the cytokinin pool was unique in each species. The largest total amount of cytokinins was detected in Morchella esculenta strain 1755 and the smallest amount, in Flammulina velutipes strain 1878. The productivity of cytokinin biosynthesis in mycelial biomass of mushrooms was the lowest in mycelial biomass of Sparassis crispa strain 314 and highest in Pleurotus ostreatus strain 551. F. velutipes strain 1878 and Cyclocybe aegerita strain 960 mycelial biomass showed the most productive zeatin riboside biosynthesis. We emphasize the need to take into account the biological activity of cytokinins, on the basis of the mycelial biomass of medicinal mushrooms, in the development of drugs or dietary supplements. Macromycetes with high rates of cytokinin biosynthesis are considered to be prospective producers of pharmacologically active compounds.