Seasonal Variation of Alkaloid Yield and Composition in a Population ofA. napellusssp.tauricum

Abstract

The tuberous roots of some oriental species of Aconitum (Ranunculaceae) have been used as one of the most important drugs in Chinese medicine as an analgesic in the treatment of rheumatism and neuralgia (1,2). It is well known that hypogeous organs of aconites contain diterpene alkaloids like aconitine, mesaconitine, and so on; remarkable qualitative and quantitative variations occur in the alkaloid content in relation with the plant species and some exogenous factors. Some years ago we have undertaken an extensive analysis of the secondary metabolites of the italian species of Aconitum (3,4,5).In this investigation, we studied the alkaloid content in samples, harvested during a one year period, of A. napellus ssp. tauricum (Wulfen) Gayer (Ranuneulaceae) growing in Cansigho (TV), in order to determine the influence of seasonal factors on such content. Plant material was extracted as described elsewhere (4); analytical HPLC was performed as reported in (5).In the examined population, the major alkaloid is represented by aconitine. The highest content of aconitine appears during summer, when the plant is flowering; the richest organs are the threadlike roots (0.44 % d. w.) and the aerial parts (leaves 0.46% and flowers 0.47% d. w.). The aconitine is also present in other parts of the plant, in particular, in the parent and in daughter roots. In the parent tuberous roots, which bear the aerial stem, the content is maximum (0.36 % d. w.) during the vegetative growth period and it decreases gradually during the year reaching the minimum (0.11% d. w.) in the quiescency. In the daughter tuberous roots, which bear the apical bud, it remains almost constant (about 0.2 % d. w.) during the year. In the fruiting stage also the seeds have a noteworthy content of aconitine.Other alkaloidsmesaconitine, N-deethylaconitine and two compounds with relative molecular messes of 629 and 688have been detected, but their content is always far less remarkable in all parts of the plant and all over the year (never greater than 0.04% d/w.).Root cultures of S. vulgaris efficiently incorporate biosynthetic precursors such as [t4Cj-labelled arginine, ornithine, putrescine, and spermidine into the pyrrolizidine alkaloid senecionine N-oxide (1). u-Difluoromethylarginine, a suicide inhibitor of arginine decarboxylase, completely prevented the incorporation of radioactivity from [t4q-arginine and [14C]-ornithine into spermidine and senecionine N-oxide. In contrast, ct-difluoromethylornithine, a specific inhibitor of ornithine decarboxylase, had no effect on the flow of radioactivity from labelled ornithine and arginine into polyamines and alkaloids. Thus, putrescine, the common precursor of polyamines and pyrrolizidine alkaloids, is exclusively derived via the arginineagmatine route. Ornithine is rapidly transformed into arginine. Recycling of the guanido moiety of agmatine back to ornithine as known from Lathyrus sativus (2) could be excluded. The enzymes catalyzing the conversion of arginine into putrescine were characterized: arginine decarbo...

Diterpenoid alkaloids

“…From the roots of this plant seven diterpenoid alkaloids have been isolated, six of which were identified as yunaconitine, crassicauline I, vilmorrianine C, talatizamine, chasmanine, and 8-deacetyl-yunaconitine. (60), and four known alkaloids, neoline, karakoline, 14acetyldelcosine, and p e n d ~l i n e . ~~ The structure of 14-benzoylneoline was determined on the basis of spectral data and by derivation of this compound from neoline.…”