Antiviral activity of a sulfoquinovosyldiacylglycerol (SQDG) compound isolated from the green alga Caulerpa racemosa

An invasive green alga, Caulerpa racemosa , collected from the South China Sea was tested for its antiviral properties. Hot water extracts and the n -butanol fraction obtained showed potent inhibition of herpes simplex virus type 1 (HSV-1) and Coxsackie virus B3 (Cox B3). A sulfoquinovosyldiacylglycerol (SQDG) compound was isolated and purified from the n -butanol fraction following further antiviral-guided fractionation. The SQDG compound exhibited an excellent antiviral effect against HSV-2, with a 50% inhibitory concentration (IC 50 ) of 15.6 μg ml -1 against both standard and clinical strains of HSV-2, but showed only moderate antiviral effects against HSV-1 and Cox B3. The SQDG compound was chemically characterized using spectroscopic methods as (2 S )-1,2-di- O -palmitoyl-3- O -(6′-sulfo-α-D-quinovopyranosyl) glycerol. This is the first isolation from C. racemosa of this SQDG compound with notable selective antiviral activity against HSV-2.