Polyphenolicic compounds in the extracts of the birch Betula pendula knotwood

Discovery of Cyclic Diarylheptanoids as Inhibitors against Influenza A Virus from the Roots of Casuarina equisetifolia

Four new cyclic diarylheptanoids, casuarinols A-C (1-3) and casuarinolide A (4), together with six known ones (5-10), were isolated from the roots of Casuarina equisetifolia. Structures were elucidated by extensive spectroscopic analysis, theoretical conformational, and electronic circular dichroism analyses. Casuarinol C (3) is a novel cyclic diarylheptanoid-aldehyde adduct. Casuarinolide A (4) represents the first structure of a seco-cyclic diarylheptanoid. Compounds 1-9 were evaluated for their anti-influenza A virus (IAV) activity against A/WSN/33 (H1N1). (-)-(M)-11-Oxo-3,12R,17-trihydroxy-9-ene-[7,0]-metacyclophane (5) displayed significant anti-IAV activity with an IC₅₀ value of 8.64 ± 2.49 μM and a CC₅₀ higher than 100 μM.

Isolation and quantification of diarylheptanoids from European hornbeam (Carpinus betulus L.) and HPLC-ESI-MS/MS characterization of its antioxidative phenolics

Detailed polyphenol profiling of European hornbeam (Carpinus betulus L.) bark, leaf, male and female catkin extracts was performed by high-performance liquid chromatography-diode array detection coupled to tandem mass spectrometry (HPLC-DAD-MS/MS). A total of 194 compounds were characterized and tentatively identified. Gallo- and ellagitannins dominated in the methanol extracts, while flavonol glycosides and methoxylated flavones prevailed in the ethyl acetate samples. In the quest for diarylheptanoids, twelve compounds were isolated by the combination of subsequent reversed-phase flash chromatographic and high-performance liquid chromatographic methods. The structural elucidation of the isolated components was performed by ultrahigh-performance liquid chromatography-Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) as well as 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Six known cyclic diarylheptanoids, together with a new compound were described in Carpinus betulus for the first time. The occurrence of a linear diarylheptanoid and a lignan has also been unprecedented in the genus Carpinus. Moreover, three known flavonol glycosides were isolated. Based on the identification of characteristic fragment ions, a new mass spectrometric fragmentation pathway for meta,meta-cyclophane-type diarylheptanoids was proposed. Quantities of the four major cyclic diarylheptanoids in European hornbeam were determined by a validated UHPLC-DAD method for the first time. The antioxidant properties of the extracts and the isolated compounds were assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Contribution of the individual constituents to the total radical scavenging activity of the samples was evaluated by an off-line DPPH-HPLC-DAD method. This allowed the identification of gallo- and ellagitannin derivatives as the constituents being primarily responsible for the antioxidant capacity of the extracts.

New cyclic diarylheptanoids from the false heartwood of Betula pubescens Ehrh

Two undescribed (1-2) and five known cyclic diarylheptanoids (3-7) were isolated from the false heartwood of white birch (Betula pubescens Ehrh.). All structures were elucidated through extensive 1D and 2D NMR experiments and HR-ESI-MS data, along with comparison of their spectroscopic data with those reported in the literature. The two new cyclic diarylheptanoids are betuladiol (1) and betulondiol (2). Extracts from false heartwood were evaluated for their antimicrobial activity against Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, Staphylococcus aureus and Cutibacterium acnes together with their antifungal activity against Candida albicans and Candida glabrata.