Microbial biotransformation of bioactive flavonoids

Biotransformations and biological activities of hop flavonoids.

Isoxanthohumol--Biologically active hop flavonoid.

The objective of this study was to evaluate the antimicrobial activity of structural analogues of xanthohumol 1, a flavonoid compound found in hops (Humulus lupulus). The agar-diffusion method using filter paper disks was applied. Biological tests performed for selected strains of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, fungi (Alternaria sp.), and yeasts (Rhodotorula rubra, Candida albicans) revealed that compounds with at least one hydroxyl group—all of them have it at the C-4 position—demonstrated good activity. Our research showed that the strain S. aureus was more sensitive to chalcones than to the isomers in which the heterocyclic ring C is closed (flavanones). The strain R. rubra was moderately sensitive to only one compound: 4-hydroxy-4’-methoxychalcone 8. Loss of the hydroxyl group in the B-ring of 4’-methoxychalcones or its replacement by a halogen atom (−Cl, −Br), nitro group (−NO2), ethoxy group (−OCH2CH3), or aliphatic substituent (−CH3, −CH2CH3) resulted in the loss of antimicrobial activity towards both R. rubra yeast and S. aureus bacteria. Xanthohumol 1, naringenin 5, and chalconaringenin 7 inhibited growth of S. aureus, whereas 4-hydroxy-4′-methoxychalcone 8 was active towards two strains: S. aureus and R. rubra.

https://www.mdpi.com/1420-3049/21/5/608/pdf/1

Antimicrobial Activity of Xanthohumol and Its Selected Structural Analogues

The aim of this study was to determine the impending antioxidant properties of different extracts of crude methanolic extract (CME) of leaves of Lannea coromandelica (L. coromandelica) and its two ethyl acetate (EAF) and aqueous (AqF) subfractions by employing various established in vitro systems and estimation of total phenolic and flavonoid content. The results showed that extract and fractions possessed strong antioxidant activity in vitro and among them, EAF had the strongest antioxidant activity. EAF was confirmed for its highest phenolic content, total flavonoid contents, and total antioxidant capacity. The EAF was found to show remarkable scavenging activity on 2,2-diphenylpicrylhydrazyl (DPPH) (EC50 63.9 ± 0.64 µg/mL), superoxide radical (EC50 8.2 ± 0.12 mg/mL), and Fe(2+) chelating activity (EC50 6.2 ± 0.09 mg/mL). Based on our in vitro results, EAF was investigated for in vivo antioxidant assay. Intragastric administration of the EAF can significantly increase levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GSH-Px) levels, and decrease malondialdehyde (MDA) content in the liver and kidney of CCl4-intoxicated rats. These new evidences show that L. coromandelica bared antioxidant activity.

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Appraisal of Total Phenol, Flavonoid Contents, and Antioxidant Potential of Folkloric Lannea coromandelica Using In Vitro and In Vivo Assays.

Chalcones are important compounds in food and cosmetics industry, and in food chemistry research. We have developed a method of synthesis of dihydrochalcones from flavanone and α,β-unsaturated chalcones by microbial hydrogenation. It has been found that bacterial strains of Rhodococcus sp. and Gordonia sp. can be successfully used in the key step of dihydrochalcones synthesis. This kind of activity has not been previously examined. Twelve microorganisms were initially screened for their ability to catalyze biotransformation reactions of selected flavonoid compounds. Of these, Rhodococcus sp. and Gordonia sp. transformed flavanone and chalcones to hydrogenation products in good isolated yield of 13–94%.

Paweł Zieliński

Papers

Microbial synthesis of dihydrochalcones using Rhodococcus and Gordonia species

Antioxidant activity and spectroscopic data of isoxanthohomol oxime and related compounds.

Mikrobiologiczna redukcja ksantohumolu i 4-metoksychalkonu

Analiza zawartości zeaksantyny i luteiny w ziarnie form kukurydzy oraz wybranych odmianach dostępnych na rynku polskim