Isolation and Characterization of Cystomexicone B

Dried and ground algal material (233.4 g) was sequentially extracted with dichloromethane (DCM) and ethyl acetate (EtOAc) at room temperature. The filtered organic extracts were combined and evaporated to afford 1.94 g of crude extract. Fractionation by gel filtration chromatography (Sephadex LH-20 column, n-hexane/DCM/methanol (7:2:1)) gave fractions F1–F6. Further chromatographic steps by gel filtration in Sephadex LH-20 (n-hexane/DCM/methanol (3:1:1)) of fraction F6, followed by medium pressure chromatography in a Lobar LiChroprep Si 60 (40–63 μm) column eluted with n-hexane/EtOAc (1:1) and silica gel column (step gradient from CHCl3/EtOAc (4:1) to 100% EtOAc), allowed isolation of cystomexicone B (6, 1.39 mg). Pure compounds gongolarone C (5, 0.17 mg, rt: 30.2 min), gongolarone B (1, 1.75 mg, 34.1 min), 6Z-1′-methoxyamentadione (2, 3.10 mg, 37.1 min), gongolarone A (4, 0.48 mg, 39.1 min), and 1′-methoxyamentadione (3, 6.22 mg, 42.1 min) were obtained by HPLC of fraction F6.4.3-5 (Phenomenex, Luna 5 μm Silica column, 100 Å, 250 × 10 mm; isocratic n-hexane/EtOAc (3:2), 10 min at 1 mL/min; gradient up to 100% EtOAc, 50 min at 2 mL/min; 100% EtOAc, 5 min, 2 mL/min). Physical properties and NMR data of compounds 1–6 were confirmed with those previously reported [16 (link),31 (link)].