Large Scale Conversion of Trilobolide into the Payload of Mipsagargin: 8-O-(12-Aminododecanoyl)-8-O-Debutanoylthapsigargin.

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.

Targeting thapsigargin towards tumors.

The skin irritating principle from Thapsia garganica was isolated, named thapsigargin and the structure elucidated. By inhibiting the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) thapsigargin provokes apoptosis in almost all cells. By conjugating thapsigargin to peptides, which are only substrates for either prostate specific antigen (PSA) or prostate specific membrane antigen (PSMA) prodrugs were created, which selectively affect prostate cancer cells or neovascular tissue in tumors. One of the prodrug is currently tested in clinical phase II. The prodrug under clinical trial has been named mipsagargin.

A comparison of headspace solid-phase microextraction and classic hydrodistillation for the identification of volatile constituents from Thapsia spp. provides insights into guaianolide biosynthesis in Apiaceae.

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.

Cytotoxic phenylpropanoids and an additional thapsigargin analogue isolated from Thapsia garganica.

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.

Tetrandrine and thapsigargin release arachidonic acid from cells in culture and stimulate prostacyclin production in rat liver cells, but may do so by different pathways.

BACKGROUND: Tetrandrine inhibits tumor cell proliferation and demonstrates chemoprevention in cancer models. Speculation on the association between its effects on K+ and Ca2+ channels and cancer chemoprevention has been made. Thapsigargin also affects K+ and Ca2+ conductance. Thapsigargin, however, is a weak tumor promoter in the two-stage model of mouse skin carcinogenesis, yet it can induce apoptosis in androgen-independent prostatic cancer cells. I have postulated that arachidonic acid release from cells in culture is associated with cancer chemoprevention. The effects of tetrandrine and thapsigargin on arachidonic acid release from human colon carcinoma and rat liver cells and prostacyclin production by rat liver cells are compared in the current studies. RESULTS: Tetrandrine and thapsigargin stimulate arachidonic acid release from human colon carcinoma and rat liver cells and prostacyclin production in rat liver cells. The stimulation by tetrandrine is not affected by incubation with actinomycin D, 100 mM KCl, the [Ca2+]i chelator, 1,2-bis (o-amino-5-fluorophenoxy) ethane-N,N,N',N',-tetraacetic acid tetraacetoxymethylester (BAPTA/AM) or in the absence of extracellular Ca2+. In contrast, stimulation by thapsigargin is inhibited by incubation with actinomycin D, 100 mM KCl, BAPTA/AM or in the absence of extracellular Ca2+. CONCLUSION: Both tetrandrine and thapsigargin stimulate arachidonic acid release, but based on the different results obtained in the presence of actinomycin D, the [Ca2+]i chelator, 100 mM KCl and in the absence of extracellular Ca2+, the mechanisms leading to this release and pathways leading to apoptosis and/or cancer chemoprevention may be different. Stimulations by tetrandrine may be mediated by activation of a secretory phospholipase A2, whereas thapsigargin's stimulations may be mediated by the cytoplasmic Ca2+-dependent phospholipase A2.