*Article* **Isolation and Total Synthesis of Stolonines A–C, Unique Taurine Amides from the Australian Marine Tunicate** *Cnemidocarpa stolonifera*

**Trong D. Tran 1, Ngoc B. Pham 1, Merrick Ekins 2, John N. A. Hooper 1,2 and Ronald J. Quinn 1,\***


Academic Editor: Sylvia Urban

Received: 19 June 2015; Accepted: 14 July 2015; Published: 22 July 2015

**Abstract:** *Cnemidocarpa stolonifera* is an underexplored marine tunicate that only occurs on the tropical to subtropical East Coast of Australia, with only two pyridoacridine compounds reported previously. Qualitative analysis of the lead-like enhanced fractions of *C. stolonifera* by LC-MS dual electrospray ionization coupled with PDA and ELSD detectors led to the identification of three new natural products, stolonines A–C (**1**–**3**), belonging to the taurine amide structure class. Structures of the new compounds were determined by NMR and MS analyses and later verified by total synthesis. This is the first time that the conjugates of taurine with 3-indoleglyoxylic acid, quinoline-2-carboxylic acid and β-carboline-3-carboxylic acid present in stolonines A–C (**1**–**3**), respectively, have been reported. An immunofluorescence assay on PC3 cells indicated that compounds **1** and **3** increased cell size, induced mitochondrial texture elongation, and *caused apoptosis in PC3 cells*.

**Keywords:** *Cnemidocarpa stolonifera*; taurine amide; PC3 cell line; immunofluorescence assay
