Pharmacophore-probe reaction guided purification to precisely identify electrophilic withanolides from Tubocapsicum anomalum Makino and their anti-TNBC activity.

Pharmacophore-probe reaction guided purification strategy can reduce the workload of natural product chemistry and raise the probability of obtaining undescribed and high-bioactive target compounds. In this study, a probe of N-acetyl cysteine (NAC) was used to confirm the pharmacophore of Tubocapsicum anomalum (Franch. et Sav.) Makino. Furthermore, a thiol probe named 4-bromothiophenol (BTP) guided the discovery of three undescribed (1-3) and nine known (4-12) electrophilic withanolides (EWs) featured potential anti-triple negative breast cancer (TNBC) pharmacophore. Notably, co-incubation with BTP made the single crystals of EW conjugates much more accessible, which facilitated the absolute configuration determination of EWs. Electrophilic natural products with the potential of thio-alkylation modification and covalent inhibition key proteins in tumor cell signal transduction pathways may display significant antitumor activity. The MTT results indicated that most EWs showed anti-TNBC activity and were expected to develop anti-TNBC candidate drugs with high selectivity and novel mechanism.

Separation and identification of tubocapsanolide MAP and tubocapsunolide A, and the structure-activity relationship of their anti-TNBC activity.

A new withanolide, tubocaapsanolide MAP (MeOH addition product) (1), as well as its known precursor tubocaapsanolide A (2) were obtained from Tubocapsicum anomalum (Solanaceae). Compound 1 was a MeOH addition product transformed from compound 2 during the process of separation using MeOH as solvent. The structures of the two withanolides including absolute configuration were elucidated by extensive spectroscopic analysis and X-ray single crystal diffraction. In the test of anti-triple negative breast cancer (TNBC) effects, tubocapsusanlide A (2) showed potent inhibitory activity against four human TNBC cell lines, while tubocapsusanlide MAP (1) exhited significantly weaker inhibitory than that of tubocapsusanlide A (2), indicating that α-ß unsaturated carbonyl unit contained in 2 was closely related to its anti-TNBC activity. The potent bioactivity displayed significant developing potential of withanolides as anti-TNBC lead compounds or drug candidates. And this report may provide some useful guidances for the preparation and bioactivity research of withanolides.

Targeting pharmacophore with probe-reactivity-guided fractionation to precisely identify electrophilic sesquiterpenes and its activity of anti-TNBC.

INTRODUCTION: Innovative strategy is urgently needed to precisely discover novel natural products as lead compounds for development of new drugs against orphan diseases such as triple-negative breast cancer (TNBC). Herein, we describe a targeting pharmacophore with probe-reactivity-guided strategy for the discovery of electrophilic sesquiterpene (ES), a class of bioactive natural product. OBJECTIVE: This study aimed to identify pharmacophore, based on pharmacophore with probe-reactivity-guided strategy for precisely discovering ESs from ethyl acetate extract of Eupatorium chinense L. (EEEChL) METHODOLOGY: MTT assay combined with ultra-performance liquid chromatography (UPLC) analysis was used to identify pharmacophore. UPLC-mass spectrometry (MS) was applied to carefully compare the intrinsic reactivity characteristics of two chemoselective nucleophilic probes: glutathione (GSH) and 4-bromothiophenol (BTP) reaction with ESs. ESs was isolated and identified from EEEChL by phytochemical methods. Furthermore, stoichiometric ratio and binding site of one typical ES 8ß-[4'-hydroxytigloyloxy]-5-desoxy-8-desacyleuparotin (HDDE) reaction with BTP were studied by UPLC-quadrupole time-of-flight (Q-TOF)-MS and two-dimensional nuclear magnetic resonance (NMR). RESULTS: Eleven ESs were identified from EEEChL, MTT assay illustrated that all of the 11 ESs possess fairly good anti-TNBC activity CONCLUSIONS: Electrophilic groups were confirmed as pharmacophore of bioactive compounds contained in EEEChL. An optimised halogenated aromatic probe BTP furnishes ES-BTP conjugates that are highly conspicuous via MS by virtue of a unique isotopic bromine signature, conjugates also have a considerable separation on C18 column. The new probe-reactivity-guided strategy can effectively improve the traditional bioassay-guided approaches, and significantly increase the probability of obtaining designated bioactive compounds.