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

Abstract

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 (IC₅₀) 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 (2S)-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.