Codakia orbicularis (Linnaeus, 1758) individuals (40-60 mm shell length) were collected from August to December 2015 by hand from Thalassia testudinum sea-grass sediments in Guadeloupe (lat 16°09′01.7′′N, long 61°33′42.9′′W). These bivalves were identified by Prof. Olivier Gros (bivalve specialist). Fresh gills from 2000 individuals were dissected, pooled, and frozen at -20°C before chemical extraction. The first study on the marine mollusk Codakia orbicularis used all soft tissues of this bivalve and led mostly to phospholipids, triglycerides, fatty acids, and sterols [1]. Some 20 years later, a second chemical study focusing on gill tissues of this bivalve led to the discovery of a new lectine, called codakine [2]. From the gills of this lucinid, we have recently isolated a new spiro-indolothiazine, named orbicularisine [3].

Three kilograms of gills were extracted by agitation in 200 mL of ethyl acetate (EtOAc) during 12 h at room temperature. The heterogeneous mixture was filtered and the filtrate stored at 4°C. The operation was repeated four times. The filtrates were pooled and evaporated under reduced pressure and then under N 2 flow. The residue (24 g) was fractionated by silica gel column chromatography to yield 17 fractions using a solvent mixture of increasing polarity (EtOAc-hexane, 20:80, EtOAc-hexane, 40:60, EtOAc-hexane, 60:40, EtOAc-hexane, 80:20, EtOAc, EtOAc-MeOH, 90:10, EtOAc-MeOH, 80:20, EtOAc-MeOH, 50:50 and MeOH). Only polar fractions that have been eluted with EtOAc-MeOH, 80:20 (F 15 , F 16 ) and EtOAc-MeOH, 50:50 (F 16 , F 17 ) were further investigated in this report. The major compounds were isolated from each fraction by repeated HPLC using an analytical Sunfire C-18 column (150 × 4.6 mm, 5 μm) and a semipreparative Sunfire C-18 column (150 × 10 mm, 5 μm). The stepwise gradient milliQ water and 2-100% MeCN (both acidified by 0.1% HCOOH, flow rate 1 and 4.5 mL/min, respectively) was used. The following compounds were isolated: compounds 1 (1.9 mg, F 16 and F 17 ), 2 (2.0 mg, F 16 , F 17 ), and 3 (0.5 mg, F 15 ). The structures of compounds 1-3 were elucidated by spectroscopic analyses, namely HR-MS and 1D and 2D NMR, but also by comparison of spectroscopic data with those reported in the literature [4, 5].