Study On Chemical Compositions Of Marine Alga Caulerpa Racemosa,Sulfated Polysaccharides From Seaweed Eucheuma Striatum And Their Biological Activities

The green alga Caulerpa racemosa and the red alga Eucheuma striatum are economic seaweeds from South China Sea. We have investigated the chemical constituents of Caulerpa racemosa , sulfated polysaccharides from Eucheuma striatum and their anti-virus effect against HSV-1 , CVB₃.Eight secondary metabolites of the alga Caulerpa racemosa have been isolated, and their structures were identified as caulerpin (â… ), (24S)-stigmast-5-ene-3β-ol palmitate (â…¡), phytosterol (â…¢),caulerpicin (â…£), stigmast-5-ene-3β,7α-diol (â…¤), (2S)-1,2-di-O-palmitoyl-3-O-(6-sulpho-α-D-quinovopyranosyl)glycerol (â…§),stigmast-4-ene-3β,6β-diol (â…¥), and a heterocyclic compound (â…¦) by spectroscopic and chemical methods. The compounds â…¡,â…¤, â…¥, â…§ were first isolated from the green alga Caulerpa. Caulerpin (â… ) as a good plant growth regulator covered 0.16% of dry weight of alga. The compound â…¢ was identified by GC-MS as a mixture of sterols and it was composed of 24-ethyl-cholest-5-en-3-ol, cholesterol, 24-methyl-cholest-5,22-dien-3-ol, 24-methyl-cholest-5-en-3-ol with relative contents of 93.3%, 2.5%, 2.2% and 2.0% respectively. Caulerpicin (â…£) was shown to consist of a mixture of ceramides derived from spinganine with C₁₆, C₁₈, C₂₀, C₂₂ and C₂₄ saturated fatty acids and C₂₂, C₂₄ monounsaturated fatty acids residues.Fatty acids in Caulerpa racemosa were determined by GC-MS. The main fatty acid is hexadecanoic acid with relative content of 34.4%. The polyunsaturated fatty acids (PUFA) covered 32.7% of total fatty acids. The main constituents of PUFA were C₁₆, C₁₈, C₂₀ unsaturated fatty acids. Nineteen elements in Caulerpa racemosa were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The contents of Mg, Ca, P, K were 3103.9mg/100g, 981.5mg/100g, 1658.4mg/100g and 2411.6mg/100g respectively.The contents of Fe, Mn, Sr, Zn, Cu were higher than other trace elements and their contents were 327.7mg/100g, 20.4mg/100g, 16.2mg/100g, 4.6mg/100g and 1.1mg/100g respectively.The crude fiber in Caulerpa racemosa was determined by acidic detergent and the contentwas 17.0%.The content of crude protein was 23.7% determined by Kjeldahl's method.We investigated the anti-virus activity of chemical constituents from Caulerpa racemosa against HSV-1 > CVB3 in vitro by MTT method and CPE inhibition method. Aqueous extract of Caulerpa racemosa (CH)exhibited obvious antivirus action against HSV-1 and CVB3. 50% inhibited concentration(IC5o) of CH for CVBj was lug/ml and the treatment index (TI) was over 1000. ICS0 of CH for HSV-1 was 6.0ug/ml and TI was 166.7. It seems to be noticeable that pure compound VI has shown good antiviral effect anginst CVB3. Its IC50 was 4ug/ml and TI was 250.Eucheuma striatum sulfated polysaccharides(ESSP) have obvious anti-CVBj effect.Its IC50 was less than 3ug/ml and TI was above 1000.We prepared the Eucheuma striatum sulfated polysaccharides with molecular weight from 5000 to 40000 by oxidative degradation with H2O2 under the ultrasonic wave.The degradating Eucheuma striatum sulfated polysaccharides had good water-solubility and the content of sulfated group was above 18.5%. The Eucheuma striatum sulfated polysaccharides with molecular weight over 20000 have shown good anti-CVB3 activity.