Marennine, a blue pigment produced by the blue diatom Haslea ostrearia, is known to have some biological activities. This pigment is responsible for the greening of oysters on the West Coast of France. Other new species of blue diatom, H. karadagensis, H. silbo sp. inedit., H. provincialis sp. inedit, and H. nusantara, also produce marennine-like pigments with similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms present a commercial potential for the aquaculture, food, cosmetics, and health industries. Unfortunately, for a hundred years, the exact molecular structure of this bioactive compound has remained a mystery. A lot of hypotheses regarding the chemical structure of marennine have been proposed. The recent discovery of this structure revealed that it is a macromolecule, mainly carbohydrates, with a complex composition. In this study, some glycoside hydrolases were used to digest marennine, and the products were further analyzed using nuclear magnetic resonance (NMR) and mass spectroscopy (MS). The reducing sugar assay showed that marennine was hydrolyzed only by endo-1,3-β-glucanase. Further insight into the structure of marennine was provided by the spectrum of ¹H NMR, MS, a colorimetric assay, and a computational study, which suggest that the chemical structure of marennine contains 1,3-β-glucan.

This study aims to isolate the RNA-dependent RNA polymerase (RdRp) gene of the dengue virus (DENV) isolates from Indonesia, determine the serotype of the local DENV strain through homology modeling, and express the recombinant RdRp protein in Escherichia coli BL21 (DE3), as the target for anti-dengue drug development. We utilize reverse transcription- polymerase chain reaction (RT-PCR) and nested PCR for serotyping the DENV isolates, obtained from Hasan Sadikin Hospital, Indonesia. Then, followed by the extraction and purification of the RdRp amplicon for gene sequencing. The resulting RdRp gene sequences are translated into amino acid sequences, which are then used for protein modeling and the construction of a recombinant plasmid for RdRp protein expression. As the result, the RdRp gene, which belongs to the non-structural protein 5 (NS5) of DENV, was successfully isolated and sequenced from DENV RNA samples. Based on serotyping results and homology modeling, the serotype of the isolate DENV was identified as serotype-3. The isolated NS5-RdRp gene from the local strain was then inserted into the pET28a(+) plasmid and transformed into E. coli BL21(DE3) as the host cell. Recombinant NS5-RdRp was predominantly found in the insoluble fraction with a molecular weight of 72 kDa. Future studies on the development of an anti-dengue drug model that confirms the inhibition of the binding domain in the recombinant RdRp protein structure will be required to provide more insight and expand the development of a universal anti-dengue strategy in Indonesia.