Feeding Deterrence and Contact Toxicity of Stemona AlkaloidsA Source of Potent Natural Insecticides

Abstract

On the basis of chronic feeding bioassays with neonate larvae of Spodoptera littoralis reared on an artificial diet, the methanolic leaf and root extracts from Stemona collinsae displayed very high insect toxicity compared to those of two Aglaia species, a commercial Pyrethrum extract, and azadirachtin, whereas S. tuberosa extracts demonstrated low activity in roots and no activity in leaves. Beyond that, in leaf disk choice tests against fifth instar larvae, S. collinsae showed strong antifeedant activity, whereas S. tuberosa was characterized by remarkable repellency. The anti-insect properties of both species were based on pyrrolo[1,2-a]azepine alkaloids, from which didehydrostemofoline (asparagamine A) was the major compound of the roots of S. collinsae, exhibiting the highest toxicity in feeding assays. Saturation and hydroxylation of the side chain in the co-occurring stemofoline and 2'-hydroxystemofoline, respectively, led to an increasing loss of activity. Contact toxicity tests with stemofoline and didehydrostemofoline exhibited even higher activities than those of Pyrethrum extract. Tuberostemonine was the dominating alkaloid in the roots of S. tuberosa, showing outstanding repellency but no toxic effects.

Stemocurtisine, the First Pyrido[1,2-a]azapine Stemona Alkaloid

“…For example, the relatively complex Stemona alkaloid, stemofoline (1), has the typical pyrrolo [1,2-a]azepine A,B-ring structure, characteristic of this class of alkaloids. 2 A few of these alkaloids do not fit these five structural groups and have a more complex bridged structure or ring structures that most likely arises from initial oxidative cleavage of the pyrrolo [1,2-a] presence of the C-and D-ring system that is typically found in the stemoamide group of alkaloids, including stemofoline (1). 1,6,[9][10][11][12][13][14][15][16][17] The 13 C/DEPT NMR spectra of 2 indicated four methine carbons, and six methylene carbons and, unlike the other Stemona alkaloids, except 1 and its didehydro and 2'-hydroxy derivatives, 2 a quaternary carbon at  120.4 was apparent, indicative of a acetal-like structure (C-9).…”

Chromosome Numbers and Other Karyological Data of Four Stemona Species (Stemonaceae) from Thailand

“…The new data support the assumption of Oginuma et al (2001), that x = 7 is the basic number for the whole genus. The uniformity in chromosome numbers is in contrast to differences observed in other character states within the genus, like morphology (Duyfjes, 1993;Tsi & Duyfjes, 2000), chemistry (Brem et al, 2002;Kaltenegger et al, 2003) and DNA-sequence analysis (Pfosser, unpubl.). These differences seem to support a classification of the genus into subgroups.…”

Investigation of Innovative Synthesis of Biologically Active Compounds on the Basis of Newly Developed Reactions

“…(11R,12S,13S)-(9Z,15Z)-11-Hydroxy-12,13-epoxoy octadecadienoic acid (22) was also synthesized from the epoxy-alcohol (19) by two steps, including Mitsunobu reaction with p-nitrobenzoic acid and hydrolysis of the resulting p-nitrobenzoate with lithium hydroxide (Chart 7).…”

“…The roots of Stemona tuberose Lour and related Stemona species (Stemonaceae) are used in Chinese traditional medicine as antitussive agents 21) and also as insecticides and antihelminthics. 22) The structural feature of 23 was based on a γ-butyrolactam that forms part of a pyrrolo[1,2-a] azepine ring system fused on a γ-butyrolactone ring with four contiguous stereogenic centers. Due to their interesting biological properties as well as their structural diversity, we are interested in developing an efficient synthetic route to this class of natural products.…”