The carotenoids extracted from two popular Asian algae forms – Chlorella ellipsoidea (CEE) and Chlorella vulgaris (CVE) – blocked growth of human colon cancer cells, the scientists found.
Lutein and zeaxanthin, more commonly known for eye health benefits, were not the only xanthophylls present in the algae but it was suggested they were the most bioactive.
They also found the extracts had a more powerful anti-cancer effect when used in combination than in isolation.
CVE was composed almost entirely of lutein and found to be 2.5 less effective at inducing apoptosis than CEE – made up of zeaxanthin along with violaxanthin and antheraxanthin.
“These results indicate that bioactive xanthophylls of C. ellipsoidea might be useful functional ingredients in the prevention of human cancers,” the researchers wrote.
But they noted both extracts were effective in battling colon cancer.
“These semi-purified extracts of CEE and CVE both inhibited the growth of HCT116 (the colon cancer cells) in a dose-dependent manner,” they said.
“Considerable evidence supports the theory that some carotenoids, such as β-carotene and lycopene, may interfere with cancer-related molecular pathways and change the expression of many proteins involved in apoptosis.”
The researchers obtained the extracts from a range of suppliers, which were washed, freeze-dried and refrigerated before being added to solutions and applied to the colon cancer sample cells.
HPLC analysis was used as well as a hemocytometer to give a cancer cell count. Both of the selected algaes were typical with a diameter of less than 10μm.
“After 24 hours of incubation, apoptotic cells began to lift from the surface monolayer, forming assorted sizes of spherical shapes,” the researchers wrote. “Apoptotic cells were more obviously apparent after treatment with CEE and CVE in concentrations of 80 μg/mL.”
The researchers called for additional study: “Further research to isolate active xanthophylls and to verify molecular mechanisms will be required to clarify fully the value of these effective constituents to cancer therapy.”
In regard to cancer, the Korean researchers noted a recent study (Wu, L. et al. “Antioxidant and antiproliferative activities of Spirulina and Chlorella water extracts”. J. Agric. Food Chem. 2005, 53, 4207–4212) that found spirulina extracts inhibited liver cancer cell growth whereas chlorella extracts produced only a minor result.
They suggested this may have been the case because of “variations in the extraction solvent”. That study had used water extraction, whereas the current research employed organic solvents.
Another recent study (Chew, B. P. et al. “Dietary lutein inhibits mouse mammary tumor growth by regulating angiogenesis and apoptosis”. Anticancer Res. 2003, 23, 3333–3339.) demonstrated lutein could inhibit growth in mouse mammary tumors by regulating angiogenesis and apoptosis.
Source: Journal of Agriculture and Food Chemistry
Web release date: October 23
“Antiproliferative Effects of Carotenoids Extracted from Chlorella ellipsoidea and Chlorella vulgaris on Human Colon Cancer Cells”
Authors: Kwang Hyun Cha, Song Yi Koo and Dong-Un Lee