CHEMICAL INVESTIGATION OF GREEN SEAWEEDS

Abstract

Seaweeds (marine algae) which have great variety of secondary metabolites with biological activities such as antibiotics, antiviral, antifungal, antitumorals, anti-inflammatory and anthelmintic, have been largely researched around the world. But there are many Sri Lankan seaweeds remain largely unexplored with high biomedical potential. Therefore, a project on chemistry and biological activity studies of Sri Lankan.seaweeds was initiated by the Natural Products Program of the Institute of Fundamental Studies. Fresh green seaweed, Chaetomorphar gracilis was collected from Arugam Bay,which lies on the seashore of Ampara District in Eastern Province. Cleaned plant material was air dried, powdered and extracted with Methanol. Since small amount of this methanol extract let to observe a white color precipitate with AgNO3, due to the presence o f NaCI; the dried methanol extract was successively fractionated with Hexane, Chloroform and Ethyl acetate. Then the dried hexane fraction was subjected to column chromatography, followed by Preparative Thin Layer Chromatography (PTLC) to give. number o f fractions. However, attempts on the isolation o f pure compounds were unsuccessful due to the close polarities o f the compounds, and unavailability o f enough material for further chromatography. Therefore, for the familiarization of spectroscopic techniques, spectral data (1H and 13C NMR, HMQC, HMBC and MS) of a compound isolated from green seaweed, Ulva lactuca were analyzed. The 13C NMR showed 29 carbon atoms and its 1H NMR clearly showed two olefinic proton signals at 8=5,32 and 8=5.11. The CIMS of it had M+ of m/z 412 with m/z 413 [M+l] as the base peak, consented with the proposed molecular formula C29H48O for (z)-stigmasta-5, 24(28)-dien-3-ol.