Dear Mikhail,

I believe that the paper I attached on the evolution of pigments in Chlorella vulgaris will be of use to you.

All the best,

Niko

Green algae are rich in chlorophyll and some of them exhibit yellow color when they are in solution. It should also take into account the presence of carotenoids and flavonoids that also exist in green algae.

Thank you, Niko Radulović 

Thank you, Ana Seca

I think that Chlorella vulgaris contains carotenoids, and more particularly,  xanthophylls such as Lutein (and that explains receiving yellow extract...)

Good Luck

Loai

Hey Mikhail. During my study we had a lot of Chlorophyll causing us issue with HPLC and the samples looked similar to yours.

Article The content and bioaccessibility of carotenoids from selecte...

Thank you, Loai Basheer !

Thank you, A. M. Naim O'Sullivan!

Chlorela vulgaris contains also beta-carotaine and lutein.Chlorophyll is readily soluble in alcohol, mostly insoluble in non polar alkanes like butane and hexane, The used solvents: isopropanol-petroleum ether in the ratio 2:1(v) may extracted the above mentioned carotenoids not chlorophylls.

Conference Paper Мicroalgae – source of biologically active substances for hu...

Chlorella vulgaris contain xanthophylls carotenoids and some amount of chlorophyll. the dominating pigment is carotenoid followed by xanthophyll which gives a yellow colour.

Apparently the yellow color is due to the xanthophyll but probably a flavonoid, why don't you take a small volume an take an UV- V spectra?,  if the absorption is more than 400 nm may be is a xanthophyll and it's less may be is a flavonoid. By other side,  using a chromogenic reaction you can have an idea, Shinoda reaction positive is for flavonoids.

Thank you, Nadezhda Traycheva Petkova!

Yes, I extracted the chlorophyll with ethanol.

Thank you, Santi Lata Sahoo!

Thank you very much, Olga Lock ! I will follow your advice!