| Marine algae have attracted much attention in the search for lead compounds to develop new drugs in recent years. Up to the present time, a variety of bioactive compounds have been found from marine algae. This paper studies on bioactive compounds from marine algae, and can be divided into two sections, one is studies on synthesis and biological properties of Martefragin A derivatives, and the other is studies on paralytic shellfish toxins-Gonyautoxins preparation and detection.Free radical-mediated lipid peroxidation has been proposed to play a critical role in several diseases, such as cardiovascular diseases, diabetes, epilepsy, tumors, AIDS and so on. This prompted many scientists to search for antioxidants compounds to protect against these diseases. Martefragin A is a new indolyloxazole compound, isolated from red alga Martensia fragilis Harvey, and has been reported to be a strong inhibitor of lipid peroxidation in rat liver microsome test. The mechanism of inhibition of NADPH- dependent lipid peroxidation is proposed to be due to radical stabilization by its extended conjugated system.The aim of the studies in the first section is the synthesis of a series of derivatives of Martefragin A and the studies on their biological activities. According to the antioxidant mechanism of Martefragin A, the 5-(3-indolyl)oxazole skeleton of Martefragin A was retained, and the side chain changed. The alkyl side chain of Martefragin A was shorted, at the same time its conjugated system by benzyl and indolyl substitute in the 2-position was extended. New derivatives series of Martefragin A were designed, and test their biological activities using p-Carotene-linoleic acid antioxidant system, DPPH free radical scavenging system, MAO model and P-388 murine leukemia strain model. During our studies, 65 compounds, including 26 target compounds, were synthesized. Among the target compounds, 25 are new compounds. Among the intermediates, 26 are new compounds. The structures of the 51 new compounds were confirmed by NMR, MS spectral data.32 compounds synthesized were assayed by p-Carotene-linoleic acid antioxidant system and DPPH free radical scavenging system. 19compounds have shown antioxidant activity in (3-Carotene-linoleic acid antioxidant system and 12 compounds have shown free radical scavenging activity in DPPH system, among them, compound 52 and 54, with two hydroxyl group showed stronger antioxidant activity than BHA and Vit E. 19 compounds synthesized were assayed by MAO model and P-388 leukemia strain model. 12 compounds have shown inhibitory MAO activity and 5 compounds had antiproliferative activity in the P-388 leukemia strain model.In the second section, four components of paralytic shellfish toxins Gonyautoxin-1, Gonyautoxin-2, Gonyautoxin-3, Gonyautoxin-4, were isolated from Alexandriun minutum Halim. The toxins were obtained by means of two different successive preparative chromatography, on the water-soluble extract taken from a mass culture of Alexandriun minutum Halim. The sample was first separated by a gel filtration chromatography; the toxin fraction obtained was then purified by an ion exchange chromatography. From the ethanol extracts of Alexandriun minutum, mixture of GTX-1, GTX-2, GTX-3 and GTX-4 was obtained. From this mixture, pure GTX-4, GTX -1, GTX -3, GTX -2 were obtained through two steps of ion exchange chromatoghraphy.The methods of using OASIS HLB and MCX cartage for sample treatment in Gonyautoxins detection were studied. We found that MXC cartage is suitable for sample treatment in paralytic shellfish toxins detection. In contrast, HLB cartage was not suitable. |
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