Investigation of antibacterial activity of Virgularia juncea extracts from the Persian Gulf

Although Iran covers most of the northern coast of the Persian Gulf, marine organisms from this region has have not been investigated very well. Herein, we aimed at a detailed analysis of antibacterial profiles against Escherichia coli ATCC, Bacillus subtilis spizizenii ATCC and Staphylococcus aureus ATCC of the marine sea pen Virgularia juncea collected from the Persian Gulf in Iran. To isolate the active ingredients, a bio-guided purification approach was used based on the MIC and MBC parameters obtained for the extracts and fractions. The n-hexane, ethyl acetate and methanol extracts of V. juncea were tested in multiple in-house bioassays, and the ethyl acetate extract showed in vitro antibacterial activity against S. aureus (MIC value 7.5 µg/mL). This extract was fractionated by using open column chromatography. The isolated active fraction (F6d), which had high activity against the S. aureus strain at the lowest concentrations (MBC value 10 µg/mL) of other fractions, was purified using the HPLC method. The pure compound Cholest-5-en-3β-ol was isolated from the active fraction (F6d), and showed moderate activity against the S. aureus bacterial strain (MBC value 50 µg/mL). This compound was identified using the GC-MS technique. This is the first study that has dealt with bioactivity profiling of V. juncea, leading to isolation and identification of pure sea pen metabolite.