Allelopathic activity of some Sri Lankan seaweed extracts and the isolation of a new brominated nonaromatic isolaurene type sesquiterpene from red alga Laurencia heteroclada harvey

Abstract

This study investigated the allelopathic activity of sixteen seaweed extracts using lettuce seed germination bioassay. The results of the preliminary investigation suggested that the methanol extracts of seven seaweeds demonstrated significant properties inhibitory to seed germination. In addition, chemical investigation of an active extract of the alleopathic Laurencia heteroclada Harvey led to the isolation of four known compounds as well as a new brominated nonaromatic isolaurene type sesquiterpene. The structural elucidation of pure compounds was carried out using spectroscopic methods and by comparison with literature. As seaweeds are highly abundant around Sri Lanka, they could be developed as an ecofriendly natural herbicide in their crude form.

Graphical Abstract

Keywords:

• Seaweeds
• brominated nonaromatic isolaurene
• nonaromatic cuparane
• allelopathic activity
• lettuce seed germination bioassay

Acknowledgments

HMH is thankful to the ICCBS for the fellowship for six months to conduct a research at the H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan.