Structures and Antibacterial Properties of Isorugosins H–J, Oligomeric Ellagitannins from Liquidambar formosana with Characteristic Bridging Groups between Sugar Moieties

Abstract

Three new ellagitannin oligomers, isorugosins H (1), I (2), and J (3), together with 11 known hydrolyzable tannins were isolated from an aqueous acetone extract of the fresh leaves of Liquidambar formosana. Their chemical structures were elucidated based on spectroscopic data and chemical conversion into known hydrolyzable tannins. The bridging mode of the valoneoyl groups between their sugar moieties has been identified only in this plant species. Additionally, the effects of the isorugosins isolated from this species on drug-resistant bacteria were evaluated and showed that isorugosin A (4) exhibited the most potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The isorugosins also had a suppressing effect on pigment formation in Pseudomonas aeruginosa. The isorugosin-protein complexes were analyzed using size-exclusion chromatography and polyacrylamide gel electrophoresis to clarify the relationship of their antibacterial properties with their protein interaction potency as hydrolyzable tannins. The results suggested that the antibacterial properties of hydrolyzable tannins are not simply a result of their binding activity to proteins, but are due to other factors such as the accessibility of polyphenolic acyl groups to bacterial membranes.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

“…; (J) Isorugosin(Shimozu et al, 2017); (K) carpescernolide A; (L) 3a,24-dihydroxylup-20(29)-en-28-oic acid(Valencia-Chan et al, 2017); (M) rasumatranin A; (N) uscharin (Yoneyama et al, 2017); (O) baeckfrutone A (Qin et al, 2018); (P) patentiflorin A (Zhang et al, 2017b); (Q) salvianan A (Zhang et al, 2017); (R) cimiricaside B (Thao et al, 2017); (S) aquilanol A (Ma et al, 2017); (T) hyperhenone G (Duan et al, 2018); (U) frustescone O; (V) dihydropyrano-coumarin derivative(Hong and Kim, 2017); (W) matteuorienate A(Huh et al, 2017); (X) t-muurolol(Pérez-Colmenares et al, 2018); (Y) bougainvinones I(Do et al, 2018). Note: for most of those compounds, the stereospecificity was represented.…”

Isolation and Characterization of Galloylglucoses Effective against Multidrug-Resistant Strains of Escherichia coli and Klebsiella pneumoniae

“…Despite the three-bond HMBC correlations between the protons at positions 9c’ (NMB4), 9e′ (NMB6), as well as those at positions 9c′ and 9e′ (NMC3) and the carbonyl carbon on the adjacent depsidic bonds, the lack of protons in proximity on the proximal galloyl unit hindered the determination of connectivity using HMBC alone ( Figure 2 ). Nevertheless, due to the deshielding effect of the proximal galloyl unit on the distal galloyl unit, the shifts resulting from protons at position 9 of the distal galloyl units appeared at the second most downfield positions in the aromatic region of the spectra and correlated with the carbonyl carbon in the depsidic bond rather than that in the underlying ester bond ( Table 1 and Table 2 ; Figures S11, S19, S27, and S35 ) [ 43 ]…”

Characterization and Identification of Bioactive Polyphenols in the Trapabispinosa Roxb. Pericarp Extract

“…Trimethylsilyldiazomethane (TMS-CHN 2 ) was purchased from Tokyo Chemical Industry (Tokyo, Japan). Each polyphenol specimen was used compounds isolated from natural sources held in our library: gallotannins [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ], 1,2-di- O -galloyl-4,6-hexahydroxydiphenoyl- d -glucose [ 45 ], cornusiin G [ 8 ], brevifolincarboxylic acid [ 39 ], urolithin M5 [ 46 ], and valoneic acid dilactone [ 41 ].…”