Triterpenoids and fatty alcohols as indicators of mangrove derived organic matter in Northern Kerala Coast, India

Abstract

Triterpenoids and fatty alcohols were identified from the sediments of five mangrove ecosystems (Kunjimangalam, Pazhayangadi, Pappinissery, Thalassery, and Kadalundi) in the northern Kerala coast, India, to illustrate the organic matter sources. Straight chain fatty alcohols in the range C12–32 were detected, and among these the long chain fatty alcohols (C20–32) were exclusively even chained compounds. Branched fatty alcohols (6,10,14-trimethyl-pentadecan-2-ol and 3,7,11,15-tetramethyl-2-hexadecanol) of bacterial origin were detected in a few observations. Twenty triterpenoids were detected from the study region in which 13 of them were sterols. Triterpenoids originated from higher plants such as stigmasterol, campesterol, β-sitosterol, taraxerol, lupeol, germanicol, β-amyrin, α-amyrin, and betulin were identified in the study. Brassicasterol, a diatom marker and dinosterol, a dinoflagellates marker were also detected in the study region. An elevated % composition of dinosterol and dissolved oxygen super-saturation were noticed in Kunjimangalam during pre-monsoon, which may suggest elevated input of algal organic matter in the mangrove system. Cholesterol transformation products such as coprostanol and epi-coprostanol were detected, which indicated the presence of fecal contamination in the sedimentary organic matter. From the ternary diagram, it was recognized that the organic matter contribution from marine algae was feeble as compared to terrestrial input.

Keywords:

• Triterpenoids
• sterols
• fatty alcohol
• mangrove
• Kerala coast

Acknowledgments

We would like to thank the Dean and Director, School of Marine Sciences, Cochin University of Science and Technology for providing the facilities. We also acknowledge the laboratory and instrumental facilities provided by the Head, Department of Chemical Oceanography and the Hon. Director, Inter-University Centre for Development of Marine Biotechnology, School of Marine Sciences, CUSAT. We are also grateful to anonymous reviewers for providing helpful and useful comments.