Structural Relationships of Stemona Alkaloids: Assessment of Species-Specific Accumulation Trends for Exploiting Their Biological Activities

Abstract

On the basis of a comparison of 42 Stemona samples, representing eight different species collected and cultivated in Thailand, species-specific accumulation trends of Stemona alkaloids were analyzed. An overview was achieved by comparative HPLC analyses of methanolic crude extracts of underground parts coupled with diode array or evaporative light scattering detectors. All major compounds were isolated and their structures elucidated by NMR and MS analyses. Protostemonine- and stichoneurine-type derivatives dominated, from which the latter characterize S. tuberosa and S. phyllantha accumulating species-specific isomers of tuberostemonine (3). The widespread S. curtisii and S. collinsiae clearly deviate by protostemonine-type derivatives dominated by stemofoline (10) and/or didehydrostemofoline (11). Further diversification within this structural type results from a mutual accumulation of derivatives with a pyrrolo- or pyridoazepine nucleus, leading to chemical variability in S. curtisii and S. aphylla.

Structural classification and biological activities of Stemona alkaloids

“…1). This classification was also supported by broad-based chemotaxonomic studies within the genus Stemona indicating two clear-cut trends either towards derivatives with a stichoneurine or protostemonine skeleton (Jiang et al 2006b;Schinnerl et al 2007;Li et al 2007a;Kongkiatpaiboon et al 2011). In contrast, derivatives with a croomine…”

“…66-76) may be regarded as artifacts produced by extraction or fractionation (Greger 2006). This was also underlined in subsequent investigations (Jiang et al 2006b;Schinnerl et al 2007;Kongkiatpaiboon et al 2011;But et al 2012). On the other hand, regarding the relatively mild extraction conditions, isolation, and purification procedures, there was no indication for the formation of artifacts in the highly oxidized stemonatuberones A-C (91-93) and stemonatuberonol A (95) (Yue et al 2014).…”

“…Further experiments led to the conclusion that tuberostemonine (52) acts as a potent repellent without toxic effects (Brem et al 2002). In view of these results it can be assumed that the recently published significant insecticidal activity of the root extract of S. collinsiae against the fly Parasacrophaga ruficornis (Sakulpanich et al 2017) can also be attributed to didehydrostemofoline (173), which was shown to be the main component of all samples of S. collinsiae collected in Thailand (Kongkiatpaiboon et al 2011).…”

“…A number of innovative strategies have been developed recently for the construction of the structurally simplest stemoamide (214) (Brito and Pirovani 2018). Moreover, extensive chromatographic comparisons of extracts from wild and cultivated Stemona species provided the basis for chemotaxonomic conclusions as well as for hypotheses regarding biosynthetic connections within this class of alkaloids (Schinnerl et al 2007;Kongkiatpaiboon et al 2011).…”

HPLC Quantitative Analysis of Insecticidal Didehydrostemofoline and Stemofoline in Stemona collinsiae Root Extracts

“…1) in S. collinsiae roots leads to its high insecticidal activity (Jiwajinda et al, 2001;Brem et al, 2002). Natural occurrence of 2'-hydroxystemofoline is always present in trace amounts (Schinnerl et al, 2007;Kongkiatpaiboon et al, 2011). Moreover, didehydroisostemofoline and isostemofoline might be regarded as artefacts probably formed by photo-isomerisation during the storage, extraction and isolation process (Jiwajinda et al, 2001;Sastraruji et al, 2005;Kongkiatpaiboon et al, 2011).…”