Agnieszka Bartmańska

Steroids' transformations in Penicillium notatum culture.

The application of Penicillium notatum genus for biotransformations of steroids has been investigated. The reactions observed include insertion of an oxygen atom into D-ring of steroids, 15alpha-hydroxylation of 17alpha-methyl testosterone derivatives, ester bond hydrolysis, and degradation of a testosterone derivatives side chain. Microbial production of testolactones, the biologically active compounds, was also achieved using this strain in up to 98% yield.

Biotransformations of Prenylated Hop Flavonoids for Drug Discovery and Production

In this review we aim to present current knowledge on biotransformation of flavonoids from hop cones with respect to type of product, catalyst and conversion. Subsequently, a comparative analysis of biological activity of prenylated hop flavonoids and their biotransformation products has been performed in order to indicate these research efforts that have good potential for application in pharmaceutical industry. There is increasing evidence that the products of biotransformation of hop prenylflavonoids, which have been little studied until recently, can be used as drugs or drug ingredients and also as standards of human drug metabolites. They can also serve as an inspiration for the design and chemical synthesis of new derivatives with higher or different biological activity. Nevertheless, much additional work, among others on determining the mechanism of action in in vivo systems, is needed to open up the way to biomedical application of these compounds.

Transformations of steroids by Beauveria bassiana.

The course of transformations of testosterone and its derivatives, including compounds with an additional C1,C2 double bond and/or a 17α-methyl group, a 17β-acetyl group or without a 19-methyl group, by a Beauveria bassiana culture was investigated. The fungi promoted hydroxylation of these compounds at position 11α, oxidation of the 17β-hydroxyl group, reduction of the C1,C2 or C4,C5 double bonds and degradation of the progesterone side-chain, leading to testosterone. The structure of 4-ene-3-oxo-steroids had no influence on regio- and stereochemistry of hydroxylation. In a similar manner, dehydroepiandrosterone was hydroxylated by Beauveria bassiana at position 11α, however, a small amount of 7α- hydroxylation product was also formed.

Transformation of xanthohumol by Aspergillus ochraceus.

Microbial transformation of xanthohumol isolated from agro‐residue (spent hops), by Aspergillus ochraceus was investigated. A new aurone, (Z)‐2″‐( 2‴ ‐hydroxyisopropyl)‐dihydrofurano[4″,5″:6,7]‐3′,4′‐dihydroxy‐4‐methoxyaurone, was obtained as a main transformation product. Three minor metabolites were identified as 2″‐( 2‴ ‐hydroxyisopropyl)‐dihydrofurano[4″,5″:3′,4′]‐2′,4‐dihydroxy‐6′‐methoxychalcone, (2S,2″S)‐2″‐( 2‴ ‐hydroxyisopropyl)‐dihydrofurano[4″,5″:7,8]‐4′‐hydroxy‐5‐methoxyflavanone and (2S,2″R)‐2″‐( 2‴ ‐hydroxyisopropyl)‐dihydrofurano[4″,5″:7,8]‐4′‐hydroxy‐5‐methoxyflavanone. Their structures were elucidated on the basis of spectroscopic evidences. The antioxidant properties of xanthohumol and its metabolites were investigated using the 2,2′‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging method. The major biotransformation product, was 8.6‐fold stronger antioxidant than xanthohumol and 2.3‐fold than ascorbic acid.

Glycosylation of Xanthohumol by Fungi

A screening test on 29 microorganisms for transformation of xanthohumol led to the selection of twelve fungal strains. One of them, Beauveria bassiana AM278, converted xanthohumol into a glucosylated derivative. This product was identified as xanthohumol 4’-O-β-D-4’’’- methoxyglucopyranoside.

Biotransformation of the phytoestrogen 8-prenylnaringenin.

In order to select microorganisms capable of transforming the potent phytoestrogen 8-prenylnaringenin, preliminary screening tests on 30 fungal cultures were performed. No reports concerning successful biotransformation of 8-prenylnaringenin by this class of organisms have been known so far. Fusarium equiseti converted 8-prenylnaringenin into 2”-(2”’-hydroxyisopropyl)-dihydrofuran-[2”,3”:7,8]-5,4’-dihydroxyfl avanon in high yield.

The Influence of Glycosylation of Natural and Synthetic Prenylated Flavonoids on Binding to Human Serum Albumin and Inhibition of Cyclooxygenases COX-1 and COX-2

The synthesis of different classes of prenylated aglycones (α,β-dihydroxanthohumol (2) and (Z)-6,4’-dihydroxy-4-methoxy-7-prenylaurone (3)) was performed in one step reactions from xanthohumol (1)—major prenylated chalcone naturally occurring in hops. Obtained flavonoids (2–3) and xanthohumol (1) were used as substrates for regioselective fungal glycosylation catalyzed by two Absidia species and Beauveria bassiana. As a result six glycosides (4–9) were formed, of which four glycosides (6–9) have not been published so far. The influence of flavonoid skeleton and the presence of glucopyranose and 4-O-methylglucopyranose moiety in flavonoid molecule on binding to main protein in plasma, human serum albumin (HSA), and inhibition of cyclooxygenases COX-1 and COX-2 were investigated. Results showed that chalcone (1) had the highest binding affinity to HSA (8.624 × 104 M−1) of all tested compounds. It has also exhibited the highest inhibition of cyclooxygenases activity, and it was a two-fold stronger inhibitor than α,β-dihydrochalcone (2) and aurone (3). The presence of sugar moiety in flavonoid molecule caused the loss of HSA binding activity as well as the decrease in inhibition of cyclooxygenases activity.

Regioselective ortho-Hydroxylations of Flavonoids by Yeast.

Natural flavonoids, such as naringenin, hesperetin, chrysin, apigenin, luteolin, quercetin, epicatechin, and biochanin A, were subjected to microbiological transformations by Rhodotorula glutinis. Yeast was able to regioselectively C-8 hydroxylate hesperetin, luteolin, and chrysin. Naringenin was transformed to 8- and 6-hydroxyderivatives. Quercetin, epicatechin, and biochanin A did not undergo biotransformation. A metabolic pathway for the degradation of chrysin has been elucidated. The metabolism of chrysin proceeds via an initial C-8 hydroxylation to norwogonin, followed by A-ring cleavage to 4-hydroxy-6-phenyl-2H-pyran-2-one.

Synthesis and Antiproliferative Activity of Minor Hops Prenylflavonoids and New Insights on Prenyl Group Cyclization

Synthesis of minor prenylflavonoids found in hops and their non-natural derivatives were performed. The antiproliferative activity of the obtained compounds against some human cancer cell lines was investigated. Using xanthohumol isolated from spent hops as a lead compound, a series of minor hop prenylflavonoids and synthetic derivatives were obtained by isomerization, cyclisation, oxidative-cyclisation, oxidation, reduction and demethylation reactions. Three human cancer cell lines—breast (MCF-7), prostate (PC-3) and colon (HT-29)—were used in antiproliferative assays, with cisplatin as a control compound. Five minor hop prenyl flavonoids and nine non-natural derivatives of xanthohumol have been synthetized. Syntheses of xanthohumol K, its dihydro- and tetrahydro-derivatives and 1″,2″,α,β-tetrahydroxanthohumol C were described for the first time. All of the minor hops prenyl flavonoids exhibited strong to moderate antiproliferative activity in vitro. The minor hops flavonoids xanthohumol C and 1″,2″-dihydroxanthohumol K and non-natural 2,3-dehydroisoxanthohumol exhibited the activity comparable to cisplatin. Results described in the article suggest that flavonoids containing chromane- and chromene-like moieties, especially chalcones, are potent antiproliferative agents. The developed new efficient, regioselective cyclisation reaction of the xanthohumol prenyl group to 1″,2″-dihydroxantohumol K may be used in the synthesis of other compounds with the chromane moiety.

Antimicrobial Properties of Spent Hops Extracts, Flavonoids Isolated Therefrom, and Their Derivatives

Hop cones preparations possess a wide range of biological activities including antimicrobial properties. In this work, we evaluated the effect of various organic extracts obtained from spent hops, as well as six hops flavonoids and their twenty natural and synthetic derivatives on human and plant microbial pathogens. Methylene chloride, acetone, ethyl acetate, and methanol were used as extractants. Seven flavonoids, among them two natural (α,β-dihydroxanthohumol and 8-prenylnaringenin) showed significant activity against methicillin sensitive and resistant Staphylococcus aureus and Staphylococcus epidermidis strains with the lowest MIC80 value of 0.5 µg/mL. The crude ethyl acetate, acetone, and methanol extracts from the spent hops exhibited antifungal activity against Fusarium oxysporum, F. culmorum, and F. semitectum with the lowest MIC50 of 0.5 mg/mL, while the methylene chloride extract exerted antifungal activity against Botrytis cinerea with the MIC50 of 1 mg/mL. The preparation obtained after the removal of xanthohumol from the spent hops crude extracts retained up to 95% of activity. These findings suggest that various spent hops extracts may be effective agents for the control of plant pathogens of economic importance, like Botrytis cinerea and Fusarium oxysporum, while some compounds from spent hops or their derivatives may become useful for staphylococcal infections.