Isosteroidal Alkaloids from Fritillaria verticillata Willd. and Their NMR Spectroscopic Characteristics

Abstract

Chemical investigation of Fritillaria verticillata Willd. led to the isolation of eight novel isosteroidal alkaloids (1-4, 6, 9-11) and four known alkaloids (5, 7-8, 12), including three unprecedented cis-fused D/E (13α, 17α) cevanine alkaloids (1-3), one rarely cis-fused E/F (22α) cevanine alkaloid (6), and one uncommon 5β-jervine-type isosteroidal alkaloid featuring a cis-fused A/B ring moiety (11). In order to establish the structures of 1, the calculated NMR with DP4+ evaluation was applied from the plausible structure candidates. The characteristic proton signals for distinguishing D/E conjunction of cevanine alkaloids were summarized. In addition, some proton and carbon signals α to nitrogen in 6 and 7 are unobservable due to the 14 N nuclear quadrupolar relaxation, based on the NMR experiments in different solvents, calculated NMR method and X-ray technology, their structures were determined. The NMR characteristics of cevanine alkaloids to distinguish orientation of long-pair on nitrogen atom with β-hydroxyl at C-20 were also concluded. The anti-inflammatory effects of compounds 1 and 4 were evaluated in LPS-activated RAW 264.7 macrophages. Compound 4 decreased LPS-induced releases of IL-1β and IL-17α in RAW264.7 cells in a dose-dependent manner. Further mechanistic study revealed that 4 suppressed the phosphorylation of IκBα and p65 subunit to regulate the NF-κB signaling pathway.

Diastereomers of Steroidal Alkaloids with Cytotoxic Activities against Non-Small-Cell Lung Cancer from the Bulbs of Fritillaria sinica

“…When the lone-pair electrons on the nitrogen atom is in α- orientation and H-22 is in β-orientation (Figure S142, structure C/D ), and when the 21-Me is on the same side (α-orientation) with lone-pair electrons, the carbon signals around the nitrogen atom would show the same abnormal shapes as for structure A (Figure S142), in CD 3 OD, such as for compounds 5 and 9 . Previously, Ma has summarized some NMR characteristics of cevanine-type alkaloids without OH at C-20 and concluded that regardless of whether the lone-pair electrons on the nitrogen atom were β-oriented or α-oriented, all the α-C and α-H signals around the nitrogen atom were unobserved in CD 3 OD, even those correlations in HSQC, HMBC, and NOESY. By analysis of the NMR data and the structures of compounds 1 – 6 and 9 – 12 (Figure S145), we have further expanded these analyses.…”

“…Subsequently, l -cysteine methyl ester (2.5 mg) was added to the aqueous layer of compound 7 in anhydrous pyridine (1 mL). And the mixture was kept at 60 °C for 1 h. Next, arylisothiocyanate (200 μL) was added to the reaction mixture and reacted at 60 °C for 1 h . After completion of the reaction, the products were analyzed by HPLC chromatography.…”

Comparative analysis of sipeimine content, metabolome and chloroplast genome in cultivated and wild varieties of Fritillaria taipaiensis

“…The unique aromatic ring structure of sipeimine gives the bulb its medicinal value and helps it exert curative effects in lung moisturizing, cough relief and phlegm elimination. 8 F. taipaiensis is found in alpine grasslands, meadows and scrub meadow areas at altitudes ranging from 2000 to 3000 m. As a valuable traditional Chinese medicine, the wild variety F. taipaiensis E.B (EB) faces restricted production and limited availability 9 due to environmental influences. Consequently, EB is scarce in the market.…”

“…The main active ingredient in the bulb is sipeimine, which belongs to the group of isosteroidal alkaloids. The unique aromatic ring structure of sipeimine gives the bulb its medicinal value and helps it exert curative effects in lung moisturizing, cough relief and phlegm elimination 8 …”