Sanctis A–C: Three Racemic Procyanidin Analogues from The Lichen Parmotrema sancti‐angelii

Abstract

The phytochemical investigation of the lichen Parmotrema sancti‐angelii afforded three racemic compounds, sanctis A–C, which feature an original dibenzo‐2,8‐dioxabicyclo[3.3.1]nonane scaffold. These compounds were structurally characterized by extensive NMR spectroscopy analyses, comparison between experimental and theoretical NMR spectroscopic data, and X‐ray crystallography. These metabolites are similar to procyanidin A and display a methyl group instead of a pendant aromatic ring at C‐9, a so far unprecedented structural feature. A biosynthetic route to sanctis A–C is proposed.

Salazinic Acid-Derived Depsidones and Diphenylethers with α-Glucosidase Inhibitory Activity from the Lichen Parmotrema dilatatum

“…Accordingly, a salient spectroscopic difference between the NMR data of 1 and 7 affected the oxygenated methylenic signals related to H 2 -8′of 7. The low-field chemical shift of H 2 -8′ along with the high-field chemical shift of the corresponding carbon are indicative of it being constrained within the deshielding zone of 2 aromatic systems in 1 [19]. The HMBC spectrum confirmed this deduction as H 2 -8′ showed crosspeaks to carbons in 2 different aromatic rings: C-2′ (δ C 153.0), C-3′ (δ C 125.1), and C-4′ (δ C 147.9) for ring B; and C-4′′ (δ C 155.9), C-5′′ (δ C 114.2), and C-6′′ (δ C 138.2) regarding ring C. The orcinol-type substitution pattern of C ring was further completed based on the chemical shift value of C-3′′ (δ C 100.2) that was indicative of it being flanked by 2 ortho-oxy substituents and further backed up by the long-range heteronuclear correlations from OH-2′′ to C-1′′ (δ C 108.5), C-2′′ (δ C 155.7), and C-3′′ (δ C 100.2) (▶ Fig.…”

“…As of 2020, lichens are still deemed to constitute a largely untapped source of bioactive specialized metabolites [17]. Our recent phytochemical investigations shed light on the wealth of the chemical diversity sheltered by Vietnamese lichen species [18], which sometimes comprised unprecedented scaffolds [19,20].…”

DP4-Assisted Structure Elucidation of Isodemethylchodatin, a New Norlichexanthone Derivative Meager in H-Atoms, from the Lichen Parmotrema tsavoense

“…UV-Vis spectra were recorded as previously described [21]. NMR spectra were measured on an Avance III 500 MHz spectrometer (Bruker, Bremen, Germany) and the solvents residual signals were used as internal references (DMSO- d 6 , at δ H 2.50 and δ C 39.5 ppm).…”

“…This strategy proved to be reliable tools in natural products structure elucidation [16,17,18]. Within the frame of our continued interest in the phytochemical study of underinvestigated Vietnamese lichen species [19,20,21,22], an original trichlorinated and depauperate in proton norlichexanthone derivative, isodemethylchodatin, was isolated from the foliose lichen species Parmotrema tsavoense . We herein report on the isolation and structure elucidation of this new compound, jointly determined by the thorough interpretation of 13 C-NMR data and ab initio methods based on Gauge-Independent Atomic Orbital (GIAO) methods.…”

Ethanol extract of male Carica papaya flowers demonstrated non‐toxic against MCF‐7, HEP‐G2, HELA, NCI‐H460 cancer cell lines

“…Compounds 1, 4, 5 and the ethanol residues of leave, flower and root of male and female C. papaya were evaluated in vitro for their cytotoxic potential against four cancer cell lines as MCF-7 HeLa, Hep-G2 and NCI-H460 by using the SRB assay with camptothecin as the positive control, as previous report. [9] 3. RESULTS AND DISCUSSION Compound 1 was obtained as a white solid.…”