What this work is about, in plain words
In a young, actively growing culture, the diatom Cylindrotheca closterium accumulates the pigment diadinoxanthin, and fucoxanthin later. The authors measured how much diadinoxanthin can be obtained and compared both pigments in experiments on tumor cell cultures: diadinoxanthin turned out to be noticeably weaker.
Fucoxanthin is an orange pigment of diatoms, and its properties are actively studied. It is usually obtained in two stages: first the biomass is grown, then unfavorable conditions are created for the cells, and the pigment accumulates. But in this stress phase some cells die, and the process is hard to predict. A similar pigment, diadinoxanthin, is accumulated earlier, while the cells are actively growing. The authors wanted to find out how much of it can be obtained and whether it shows the same activity as fucoxanthin in experiments.
C. closterium was grown in 3 L laboratory photobioreactors. Both pigments were isolated in pure crystalline form. Their activity was then compared in two ways: by computer modelling of binding to the HER2 protein and by experiments on four human ovarian cancer cell lines in vitro.
According to the authors, in the active growth phase diadinoxanthin accumulated at an average rate of 1.22 mg/(L·day), and fucoxanthin at 0.64 mg/(L·day) over the whole cycle. By the authors' calculation, in a continuous-flow culture the yield of diadinoxanthin could be another 7.5 times higher. In the cell experiments, fucoxanthin reduced cell viability at a concentration of about 19 µM. Diadinoxanthin, even at 100 µM, reduced it by only 40 %, that is, it was noticeably weaker.
The work provides data on how to obtain diadinoxanthin and shows that it cannot replace fucoxanthin in terms of this activity.
Limitations. In vitro cell culture experiments and a computer model are not a clinical study and not proof of an effect in humans. The yield in a continuous-flow culture was calculated, not measured.