ABSTRACT
In spite of the impressing cytotoxicity of thapsigargin (Tg), this compound cannot be used as a chemotherapeutic drug because of general toxicity, causing unacceptable side effects. Instead, a prodrug targeted towards tumors, mipsagargin, was brought into clinical trials. What substantially reduces the clinical potential is the limited access to Tg and its derivatives and cost-inefficient syntheses with unacceptably low yields. Laser trilobum, which contains a structurally related sesquiterpene lactone, trilobolide (Tb), is successfully cultivated. Here, we report scalable isolation of Tb from L. trilobum and a transformation of Tb to 8-O-(12-aminododecanoyl)-8-O-debutanoylthapsigargin in seven steps. The use of cultivated L. trilobum offers an unlimited source of the active principle in mipsagargin.
Subject(s)
Antineoplastic Agents, Phytogenic/chemistry , Apiaceae/chemistry , Butyrates/chemistry , Chemistry Techniques, Synthetic , Furans/chemistry , Thapsigargin/analogs & derivatives , Antineoplastic Agents, Phytogenic/isolation & purification , Apiaceae/metabolism , Butyrates/isolation & purification , Carbon Dioxide/chemistry , Chromatography, Supercritical Fluid/methods , Fruit/chemistry , Fruit/metabolism , Furans/isolation & purification , Humans , Molecular Structure , Neoplasms/drug therapy , Neoplasms/pathology , Plant Extracts/chemistry , Sarcoplasmic Reticulum Calcium-Transporting ATPases/antagonists & inhibitors , Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism , Thapsigargin/isolation & purificationABSTRACT
INTRODUCTION: Thapsia spp. (Apiaceae) are the major natural source of polyoxygenated guaianolide sesquiterpene lactones known as thapsigargins, which induce apoptosis in mammalian cells via a high affinity inhibition of the sarco/endoplasmic reticulum Ca(2+) ATPase. The mechanism of biosynthesis of thapsigargins has not been elucidated, and probable biochemical precursors such as hydrocarbon or oxygenated sesquiterpenes have not been identified in previous phytochemical analyses of essential oils from this genus. OBJECTIVE: To investigate the utility of solid phase micro-extraction (SPME), when compared with classical essential oil distillates, for identifying potential precursors of guaianolide sesquiterpene lactones from Thapsia garganica L. and Thapsia villosa L. type II. METHODOLOGY: A systematic description of the volatile components of roots, flowers, stems and fruits of T. villosa and of root, flower and fruits of T. garganica was constructed via GC-MS analyses of SPME-adsorbed compounds and of essential oils obtained through hydrodistillation of the same tissues. RESULTS: The sesquiterpenoids δ-cadinene, α- and δ-guaiene, elemol and guaiols were found to be major volatile constituents of the roots of T. garganica and T. villosa trapped using SPME. In contrast, these sesquiterpenoids were not detected or were at negligible levels in essential oils, where sesquiterpenoids are potentially converted to azulenes during hydrodistillation. CONCLUSION: The new data reported in this study demonstrates that SPME is a valuable tool for the identification of volatile sesquiterpenes when compared with analysis of essential oils, and we postulate that guaiene is the likely precursor of guaianolide sesquiterpenes from Thapsia.
Subject(s)
Oils, Volatile/isolation & purification , Sesquiterpenes, Guaiane/biosynthesis , Solid Phase Microextraction/methods , Thapsia/chemistry , Thapsigargin/isolation & purification , Azulenes/metabolism , Distillation , Flowers/chemistry , Fruit/chemistry , Oils, Volatile/analysis , Oils, Volatile/chemistry , Plant Oils/analysis , Plant Oils/chemistry , Plant Oils/isolation & purification , Plant Roots/chemistry , Plant Stems/chemistry , Sesquiterpenes, Guaiane/metabolism , Thapsia/metabolism , Thapsigargin/analysis , Thapsigargin/chemistryABSTRACT
Four phenylpropanoids and a thapsigargin analogue have been isolated from the fruits of Thapsia garganica. A spectroscopic method for elucidating the relative stereochemistry at the two pairs of stereogenic centers in the phenylpropanoids has been developed. The phenylpropanoids were found to be potent cytotoxins.