Abstract
Tisochrysis lutea is a marine haptophyte rich in omega-3 polyunsaturated fatty acids (e.g., docosahexaenoic acid (DHA)) and carotenoids (e.g., fucoxanthin). Because of the nutraceutical applications of these compounds, this microalga is being used in aquaculture to feed oyster and shrimp larvae. In our earlier report, T. lutea organic crude extracts exhibited in vitro cytotoxic activity against human hepatocarcinoma (HepG2) cells. However, so far, the compound(s) accountable for the observed bioactivity have not been identified. Therefore, the aim of this study was to isolate and identify the chemical component(s) responsible for the bioactivity observed. Bioassay-guided fractionation through a combination of silica-gel column chromatography, followed by preparative thin layer chromatography (PTLC), led to the isolation of two diastereomers of a monoterpenoid lactone, namely, loliolide (1) and epi-loliolide (2), isolated for the first time in this species. The structural elucidation of both compounds was carried out by GC-MS and 1D (1H and 13C APT) and 2D (COSY, HMBC, HSQC-ed, and NOESY) NMR analysis. Both compounds significantly reduced the viability of HepG2 cells and were considerably less toxic towards a non-tumoral murine stromal (S17) cell line, although epi-loliolide was found to be more active than loliolide.
Highlights
In recent years, natural products derived from microalgal biomass produced at pilot scale have attracted great attention in drug discovery [1]
It is reported as a topoisomerase II inhibitor, leading to cell-cycle arrest followed by cell death [20]
It was found that the DCM extract was the most active compared to the hexane and acetone extracts, decreasing HepG2 cell viability down to 24.7% at a concentration of 125 μg/mL (Figure 1), resulting in an IC50 of 85.1 μg/mL (CI95 % 73.1 to 99.1 μg/mL)
Summary
Natural products derived from microalgal biomass produced at pilot scale have attracted great attention in drug discovery [1]. Because of their unique biochemical pathways and great adaptability to various environmental conditions such as high salinity, low or high temperatures, high light intensities, and a wide pH range, microalgae can be viable alternatives to terrestrial plants in producing highly valuable natural precursors with potential bioactivity [2]. Mar. Drugs 2020, 18, 567; doi:10.3390/md18110567 www.mdpi.com/journal/marinedrugs. Mar. Drugs 2020, 18, 567 of mollusks, fish, and crustaceans in the aquaculture industry. It has been described that T. lutea is able to accumulate significant levels of n-3 polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA), and of xanthophylls such as fucoxanthin, which play an important role in the prevention and treatment of human diseases [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
