Yunnanensine type indole and seco stemmadenine-yunnanensine type bisindole alkaloids from the bark of Alstonia scholaris

Document Type

Article

Publication Date

6-1-2024

Abstract

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 -valles- amine N -oxide ( 5 ), 6,7- seco -19,20 alpha-epoxyangustilobine B ( 6 ), 16 R -19,20- E -isositsirikine ( 7 ), N -demethylal- stogustine 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 mu M), MDA-MB-231 (IC 50 32.0 +/- 2.2 mu M), and MDA-MB-468 (IC 50 34.1 +/- 3.3 mu M) cancer cell lines, while N -for- mylyunnanensine ( 1 ) did not show appreciable cytotoxicity against any of the tested cell lines.

Keywords

Alstonia scholaris, Apocynaceae, Alkaloids, Bisindole, Rotamers

Publication Title

Phytochemistry Letters

Divisions

CHEMISTRY

Volume

61

Publisher

Elsevier

Publisher Location

RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS

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