Two new phenolic compounds from the lichen Parmotrema cristiferum growing in Vietnam

Two New α‐Glucosidase Inhibitory Depsidones from the Lichen Parmotrema cristiferum (Taylor) Hale

“…The long-range HMBC of H 3 -8''' to C-4''' (δ C 154.6) determined the chemical shift of C-4''', The downfield 1 H-NMR chemical shift of H 3 -8''' and the upfield 13 C signal of C-1''' indicated that the carboxylic acid group was attached at C-1''', This is commonly found in the monoaromatic lichen compounds or the A-ring of depsides. [1] The hemiacetal proton H-9' (δ H 6.86) appeared in 1 H-NMR, but carbon C-9' could not be found in HSQC and 13 C-NMR spectra. The same phenomena were found in similar compounds such as praesorether C from P. Praesorediosum, [14] parmosidone F from P. dilatatum, [9] and parmetherine D from P. indicum [15] due to the minute amount of 1.…”

“…[1] Additionally, in the D-ring, HMBCs of H-3''' (δ H 6.06) to C-1''' (δ C 104.1) and C-2''' (δ C 164.4), of H-5''' (δ H 6.26) to C-1''' and C-3''' (δ C 101.5), and of H 3 -8''' (δ H 2.50) to C-1''', C-5''' (δ C 110.3), and C-6''' (δ C 145.2) defined the chemical structure as a D-ring. The long-range HMBC of H 3 -8''' to C-4''' (δ C 154.6) determined the chemical shift of C-4''', The downfield 1 H-NMR chemical shift of H 3 -8''' and the upfield 13 C signal of C-1''' indicated that the carboxylic acid group was attached at C-1''', This is commonly found in the monoaromatic lichen compounds or the A-ring of depsides. [1] The hemiacetal proton H-9' (δ H 6.86) appeared in 1 H-NMR, but carbon C-9' could not be found in HSQC and 13 C-NMR spectra.…”

“…Its The above spectroscopic data indicated that 2 was a depsidone having three aromatic rings. [2,4,7] The 13 C-NMR chemical shifts of two aldehyde groups were determined by the signals at δ C 194.8 and 194.5 in the JMOD and 13 C-NMR spectra of 2 (Figures S11-S13). These aldehyde groups were also supported by HR-ESI mass data.…”

“…[12] Terpenoids and steroids were also isolated from this lichen, including norreticulatin, anadensin, fusicoauritone, ergosterol, and botulin. [13] Cristiferide A and norreticulatin displayed potent inhibition against α-glucosidase. [12,13] Previous research found that the Vietnamese lichen P. cristiferum contains potent α-glucosidase inhibitors.…”

“…1 H-and13 C-NMR data (500 and 125 MHz) of 1 and 2 in acetone-d 6 . concentrations around the IC 50 values, and the mean values were retained.…”