Mekanisme Proses Tahap Ekstraksi Karagenan dari Eucheuma Cottonii Menggunakan Pelarut Alkali (The Mechanism Of Carrageenan Extraction From Eucheuma Cottonii Using Alkaline Solvent)

Penelitian ini bertujuan mengembangkan proses ekstraksi karagenan dari rumput laut Eucheuma cottonii dengan mempelajari pengaruh jenis pelarut pada tahap ekstraksi, yaitu air suling, KOH, dan NaOH terhadap rendemen dan sifat gel karagenan. Ekstraksi dilakukan dengan perbandingan bobot rumput laut – volume pelarut dijaga tetap yaitu 1:50 g/mL pada 80oC. Cuplikan diambil setiap interval waktu tertentu untuk dianalisis. Karagenan dalam filtrat diendapkan dengan etanol dan serat yang dihasilkan dikeringkan sampai bobot konstan. Spektrum infra merah menunjukkan bahwa karagenan yang dihasilkan identik dengan jenis kappa. Air suling merupakan pelarut yang efisien untuk mendapatkan rendemen yang tinggi, tetapi kekuatan gel karagenan yang dihasilkan rendah. Konsentrasi KOH semakin tinggi akan menghasilkan karagenan dengan kadar sulfat semakin rendah dan kekuatan gel meningkat. Pada tahap ekstraksi menggunakan alkali, terjadi peristiwa pertukaran ion antara kation dalam pelarut dengan ion sulfat dalam rumput laut. Dibandingkan dengan kation Na, kation K mampu membentuk agregasi heliks yang terindikasi berdasarkan kekuatan gel yang lebih kuat

Antioxidant and cytotoxic activities of sulfated polysaccharides from five different edible seaweeds

In recent times, there has been a growing interest in the exploration of antioxidants and global trend toward the usage of seaweeds in the food industries. The low molecular weight up to 14 kDa sulfated polysaccharides of seaweeds (Portieria hornemannii, Spyridia hypnoides, Asparagopsis taxiformis, Centroceras clavulatum and Padina pavonica) were evaluated for in vitro antioxidant activities and cytotoxic assay using HeLa cell line and also characterized by FTIR. The high yield (7.74% alga dry wt.) of sulfated polysaccharide was observed in P. hornemannii followed by S. hypnoides (0.69%), C. clavulaum (0.55%) and A. taxiformis (0.17%). In the brown seaweed P. pavonica, the sulfated polysaccharide yield was 2.07%. High amount of sulfate was recorded in the polysaccharide of A. taxiformis followed by C. clavulaum, P. pavonica, S. hypnoides and P. hornemannii as indicative for bioactivity. The FTIR spectroscopic analysis supports the sulfated polysaccharides of S. hypnoides, C. clavulatum and A. taxiformis are similar to agar polymer whereas the spectral characteristics of P. hornemannii have similarities to carrageenan. The higher DPPH activity and reducing power were recorded in the polysaccharide of brown seaweed P. pavonica than the red seaweeds as follows: DPPH activities: S. hypnoides > A. taxiformis > C. clavulatum > P. hornimanii; Reducing power: A. taxiformis > P. hornimanii > S. hypnoides > C. clavulatum. The polysaccharide fractions contain up to 14 kDa from red seaweeds P. hornemannii and S. hypnoides followed by brown seaweed P. pavonica exhibit cytotoxic activity in HeLa cancer cell line (and are similar to structural properties of carrageenan extracted from P. hornemannii). The low molecular weight agar like polymer of S. hypnoides and alginate like brown seaweed P. pavonica showing better in vitro antioxidant activities that are capable of exhibiting cytotoxicity against HeLa cell line can be taken up further in-depth investigation for nutraceutical study.University of Algarve: DL 57/2016info:eu-repo/semantics/publishedVersio

Raman Signal Enhancement Dependence on the Gel Strength of Ag/Hydrogels Used as SERS Substrates

A series of hydrogel samples composed of Ag nanoparticles dispersed in carrageenan gels have been prepared and used in SERS studies. These studies demonstrate the dependence of the enhancement of the SERS signal on the strength of the Ag/polysaccharide hydrogel. 2,2'-Dithiodipyridine was used as the analyte probe. Several strategies were employed in order to vary the gel strength. These include the increase of the polysaccharide content in the gel, the addition of KCl as cross-linker, and the variation of the type of carrageenan (kappa, l, lambda) network. An increase in the gel strength originates an increase in the SERS enhancement observed. The results have been interpreted considering hot spots increase due to the formation of Ag particles nanojunctions as the biopolymer matrix tends to rearrange into stronger gels. This is the first report showing that there is a direct correlation between the gel strength of a hydrogel composite used as substrate and its analytical SERS sensitivity