Phytotoxic Withanolides fromJaborosarotacea

Abstract

Twelve new withanolides were isolated from the aerial part of Jaborosa rotacea: five had a spiranoid delta-lactone (1-5); one contained a 26,12-delta-lactone and a C-12-C-23 bond (6); five corresponded to trechonolide-type withanolides with configuration at C-23 opposite of those previously isolated (7, 8, 10-12); two of these have an additional oxido-bridge between C-21 and C-24; finally a withanolide with a hemiketal ring formed between a 21-hydroxyl and a 12-ketone (13) and the closely related jaborosalactone R were also isolated. New compounds were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS). The structures of the spiranoid withanolide and of the epimer of trechonolide A were confirmed by X-ray diffraction studies. Compounds 4, 5, 6, and 8 showed selective phytotoxicity toward monocotyledoneous and dicotyledoneous species.

Withanolides and Related Steroids

“…Tettamanzi et al had reported the isolation of a closely related epoxyg-lactol from J. lanigera for which the (23R) configuration was proposed (175); this compound had 13 C NMR data identical to 382 for C-12-C-18 and C-20-C-28 indicating that both compounds should have the same configuration in the side chain, hence the revised structure 386 is proposed. Thus so far, all known epoxy-g-lactones and lactols have the same configuration at C-23, opposite to that of trechonolide A. Jaborosalactones 35 (387) and 36 (388) isolated from J. rotacea would result from cyclization of a 21-hydroxy-epoxy-g-lactone (120). It should be noted that to date, trechonolides have been reported in nine of the thirteen Jaborosa species studied.…”

“…), thus the methyl ketal 255 is probably formed during isolation. Nicotra et al reported the isomeric clorohydrin, jaborosalactone 37 (256), from Jaborosa rotacea (120). Interestingly, the D 2 -withanolide 257 was present in Jaborosa caulescens var.…”

“…Careful inspection of the original X-ray data for trechonolide A (169,170) confirmed the (23S) configuration. The C-23 epimers of jaborotetrol and jaborochlorotriol (370 and 371) were also isolated from J. rotacea and shown to be (23R) (120) Several withanolides structurally related to trechonolide A with the classical variations in the substitution pattern of rings A and B, have been subsequently isolated from different species of Jaborosa. Jaborotetrol (372), previously isolated from J. magellanica, and trechonolide A (368) are the most commonly found.…”

“…As already observed with the sativolides, the C-12 hemiketal of the trechonolides is highly reactive towards alcohols and even small amounts of methanol or ethanol used during the isolation procedure will give the 12-O-methyl or ethyl derivatives. For example, when 370 was dissolved in deuterochloroform containing a few drops of deuteromethanol (to enhance solubility), the 12-O-trideuteromethyl derivative was formed (120) OH products. The 6,19-oxygen bridge present in 379 is an unusual functionality for a natural product.…”

Derivados citotóxicos de vitanolidos isolados das folhas de Acnistus arborescens

“…Estes foram primeiramente citados na literatura em 1962, mas sua elucidação estrutural só aconteceu em 1966 com a descrição estereoquímica da vitaferina 1 (Figura 1) isolada das folhas de Withania somnifera, popularmente conhecida na Índia como Ashwaganha. 2 Os vitanolidos têm sido isolados de plantas de vários gêneros, como exemplo podem ser citados: Acnistus, [3][4][5][6][7][8] Datura, 9 Jaborosa, 10 Physalis 11 e Withania, 12,13 todos da família Solanaceae, e despertam interesse por apresentarem diversas atividades biológicas, algumas delas como antitumoral, 4-8 diurética, 13 indução de quinona redutase 5,14 e imunossupressora. 15 Outros esteroides que são encontrados na famíla Solanaceae incluem glicosídeos e alcaloides esteroidais, compostos presentes nos gêneros Cestrum e Solanum, sendo este último gênero o que possui o maior número de espécies catalogadas.…”