Antimicrobial Prenylated Isoflavones from the Leaves of the Amazonian Medicinal Plant Vatairea guianensis Aubl.

Abstract

Vatairea guianenis Aubl. (Fabaceae) is an Amazonian medicinal plant species traditionally used for treating skin diseases. In an initial screening, a V. guianensis leaf extract and its subextracts showed antibacterial and antifungal activities. The EtOAc subextract was selected for chemical workup and afforded five known (1−4 and 8) and six undescribed isoflavones, vatairenones C−H (5−7 and 9−11). All isoflavones are prenylated in position C-8, displaying either chain-prenylated (1−7) or ring-closed forms (8−11). The most bioactive compound (3) exhibited in vitro activity against clinically relevant bacteria and fungi with IC 50 values ranging from 6.8 to 26.9 μM. Due to its broad antimicrobial activity and low general toxicity, compound 3 is a potential lead compound for structural modifications. The results of the present study support the ethnomedicinal use of V. guianensis in the treatment of dermatological disorders. 1 H NMR spectra of some of the isolated compounds showed intricate signal patterns, which might explain repeated errors in assigning the correct structure of the isoflavonoid B-ring in the literature and which we resolved by higher order spectra simulations.

Phenolic Compounds in Bacterial Inactivation: A Perspective from Brazil

“…Of the isoflavonoids isolated from the leaves of Vaitera guianensis , the substances that showed antibacterial activity against methicillin-resistant S. aureus were the prenylated isoflavones 5,7,3′-trihydroxy-4′-methoxy-8-prenylisoflavone ( 5 ), 8-(3-hydroxy-3-methylbutyl)-5,7,3′,4′-tetrahydroxyisoflavone ( 6 ), 8-(3-hydroxy-3-methylbutyl)-5,7,4′-trihydroxy-3′-methoxyisoflavone ( 7 ), and 8-(3-hydroxy-3-methylbutyl)-5,7,3′-trihydroxy-4′-methoxyisoflavone ( 8 ) ( Figure 3 ; Table 1 ). Compound ( 5 ) exhibited the highest S. aureus inhibition value at the half-maximal inhibitory concentration (IC 50 ) of 6.8 µM and was also active against E. faecium (IC50 of 12.8 µM) [ 18 ]. In work carried out to investigate the effect of soybean flavone on the DNA and RNA of S. aureus (ATCC 26112), the authors indicated that isoflavones were effective in inhibiting the activity of topoisomerase I and II enzymes, responsible for the dynamic control of changes in nucleic acids, and their inhibition affected nucleic acid synthesis and bacterial growth [ 71 ].…”

Perplexing Polyphenolics: The Isolations, Syntheses, Reappraisals, and Bioactivities of Flavonoids, Isoflavonoids, and Neoflavonoids from 2016 to 2022

“…Compounds 76–81 are isoflavones isolated from the leaves of Vatairea guianenis . They all feature C8 prenylation, with compounds 76–78 displaying chain prenylation and compounds 79–81 displaying ring-closed prenylation [ 41 ]. Compound 82 is a flavanonol isolated from Dietes bicolor’s leaves.…”

“…From the isolates, compounds 1 , 10 , 27–34 , 55 , 79 , 81 , 148 , 227 , 228 , 248 , and 249 were not tested for unspecified reasons [ 19 , 25 , 31 , 38 , 41 , 60 , 76 , 79 ]. Additionally, compound 82 was not tested due to the putative inactivity of flavanonols in the antigen-induced degranulation assay in RBL-2H3 cells [ 42 ].…”

“…Notably, all active compounds showed chain-open prenylation, while none of the compounds with ring-closed isoprene moieties were effective. Additionally, the marginally better antibacterial activity of compound 76 against MRSA indicated that the C3′ and C4′ hydroxyl groups are minor determinants of bioactivity [ 41 ].…”

Chemical and Biological Evaluation of Amazonian Medicinal Plant Vouacapoua americana Aubl

“…As part of our ongoing research on Amazonian medicinal plants [ 12 , 13 , 14 , 15 ], we investigated the phytochemical profile of V. americana stem bark leading to the identification of the essential oil composition and the isolation of five diterpenoids ( 1 – 5 , Figure 1 ), of which 1 was isolated from a natural source for the first time. In addition, we evaluated the isolated metabolites for their bioactivity potential towards a small panel of antimicrobial and cytotoxicity assays.…”