Synthesis of bilocularin A carbamate derivatives and their evaluation as leucine transport inhibitors in prostate cancer cells

Macrolide sesquiterpene pyridine alkaloids from Celastrus monospermus and evaluation of their immunosuppressive and anti-osteoclastogenesis activities

Phytochemical investigation of the stems of Celastrus monospermus Roxb enabled isolation and identification of fifteen new macrolide sesquiterpene pyridine alkaloids (1-15) along with five known analogues. Their structures were elucidated by comprehensive spectroscopic analysis (NMR, HRESIMS, IR, UV), chemical hydrolysis, and single crystal X-ray diffraction analysis. Bioassay of the abundant isolates revealed that seven compounds inhibited the proliferation of B lymphocytes with IC50 values ranging between 1.4 and 19.9 μM. Among them, celasmondine C (3) could significantly promote the apoptosis of activated B lymphocyte, especially late-stage apoptosis. Besides, compounds 3, 16, and 20 exhibited potent suppression of osteoclast formation at a concentration of 1.0 μM. This investigation enriched the chemical diversity of macrolide sesquiterpene pyridine alkaloids, and supported evidence for the development of new immunosuppressive and anti-osteoclastogenesis agents.

Semisynthesis and Cytotoxic Evaluation of an Ether Analogue Library Based on a Polyhalogenated Diphenyl Ether Scaffold Isolated from a Lamellodysidea Sponge

The known oxygenated polyhalogenated diphenyl ether, 2-(2',4'-dibromophenoxy)-3,5-dibromophenol (1), with previously reported activity in multiple cytotoxicity assays was isolated from the sponge Lamellodysidea sp. and proved to be an amenable scaffold for semisynthetic library generation. The phenol group of 1 was targeted to generate 12 ether analogues in low-to-excellent yields, and the new library was fully characterized by NMR, UV, and MS analyses. The chemical structures for 2, 8, and 9 were additionally determined via single-crystal X-ray diffraction analysis. All natural and semisynthetic compounds were evaluated for their ability to inhibit the growth of DU145, LNCaP, MCF-7, and MDA-MB-231 cancer cell lines. Compound 3 was shown to have near-equivalent activity compared to scaffold 1 in two in vitro assays, and the activity of the compounds with an additional benzyl ring appeared to be reliant on the presence and position of additional halogens.

Using a Bioactive Eremophila-Derived Serrulatane Scaffold to Generate a Unique Carbamate Library for Anti-infective Evaluations

The known Eremophila microtheca-derived diterpenoid 3,7,8-trihydroxyserrulat-14-en-19-oic acid (1) was targeted for large-scale purification, as this bioactive plant compound has proven to be an attractive scaffold for semisynthetic studies and subsequent library generation. Compound 1 was converted to a selectively protected trimethyl derivative, 3-hydroxy-7,8-dimethoxyserrulat-14-en-19-oic acid methyl ester (2), using simple and rapid methylation conditions. The resulting scaffold 2 was reacted with a diverse series of commercially available isocyanates to generate an 11-membered carbamate-based library. The chemical structures of the 11 new semisynthetic analogues were fully characterized by spectroscopic and spectrometric analysis. All natural products and semisynthetic compounds were evaluated for their anthelmintic, antimalarial, and anti-HIV activities. Compound 3 was shown to elicit the greatest antiplasmodial activity of all compounds tested, with IC₅₀ values of 4.6 and 11.6 μM against Plasmodium falciparum 3D7 and Dd2, respectively. Compound 11 showed the greatest inhibition of development to fourth-stage Haemonchus contortus larvae (L4) and induction of a skinny (Ski) phenotype (67.5% of nematodes) at 50 μM. Compound 7, which inhibited 59.0% of HIV production at 100 μg/mL, was the carbamate analogue that displayed the best antiviral activity.

Identification of Anthelmintic Bishomoscalarane Sesterterpenes from the Australian Marine Sponge Phyllospongia bergquistae and Structure Revision of Phyllolactones A-D

High-throughput screening of the NatureBank marine extract library (7616 samples) identified an extract derived from the Australian marine sponge Phyllospongia bergquistae with activity against Hemonchus contortus (barber's pole worm), an economically important parasitic nematode. Bioassay-guided fractionation of the CH₂Cl₂/MeOH extract from P. bergquistae led to the purification of four known bishomoscalarane sesterterpenes, phyllolactones A-D (1-4). The absolute configurations of phyllolactones B (2) and C (3) were determined by single-crystal X-ray diffraction analysis; literature and data analyses revealed the need for these chemical structures to be revised. Compounds 2-4 induced a lethal, skinny (Ski) phenotype in larvae of H. contortus at concentrations between 5.3 and 10.1 μM. These data indicate that the bishomoscalarane sesterterpene structure class warrants further investigation for nematocidal or nematostatic activity.