| Abstrakt: |
Two previously undescribed monoterpenoid indole alkaloids, N -formylyunnanensine (1) and scholaphylline (2), along with eight known alkaloids, namely, 19,20- E -vallesamine (3), 19,20- Z -vallesamine (4), 19,20- E -vallesamine N -oxide (5), 6,7- seco -19,20α-epoxyangustilobine B (6), 16 R -19,20- E -isositsirikine (7), N -demethylalstogustine N -oxide (8), E -vallesiachotamine (9), and Z -vallesiachotamine (10), were isolated from the bark of Alstonia scholaris. Alkaloid 1 was determined to be the N -formyl derivative of the known alkaloid, yunnanensine, comprising a pair of inseparable E / Z -formamide rotamers, while scholaphylline (2) was identified as the first member of the seco stemmadenine-yunnanensine type bisindole alkaloid. The structures of these alkaloids and their absolute configurations were established based on detailed analysis of the spectroscopic data in conjunction with the TDDFT-ECD method. A possible biogenetic pathway to 1 and 2 , involving stemmadenine as the primary precursor, was proposed. Scholaphylline (2) showed modest cytotoxicity against Panc1 (IC 50 27.7 ± 5.1 µM), MDA-MB-231 (IC 50 32.0 ± 2.2 µM), and MDA-MB-468 (IC 50 34.1 ± 3.3 µM) cancer cell lines, while N -formylyunnanensine (1) did not show appreciable cytotoxicity against any of the tested cell lines. [Display omitted] • Two new indole alkaloids were isolated from the bark of Alstonia scholaris. • N -Formylyunnanensine was obtained as a pair of inseparable E / Z -formamide rotamers. • Scholaphylline is the first secostemmadenine-yunnanensine type bisindole alkaloid. [ABSTRACT FROM AUTHOR] |
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