Vietnam possesses a diverse microalgal and cyanobacterial flora, including

many endemic species; however, studies on their chemical constituents and

biological activities remain limited. In this study, we collected samples from

Hanoi, followed by isolation, identification, and biomass cultivation.

Methanolic extracts of the obtained strains were evaluated for in vitro

anticancer activity against HepG2 and SK-LU-1 cell lines. A total of 15 strains

belonging to eight genera were isolated and identified. Among them, eight

strains exhibited cytotoxic activity. Anabaena smithii and Anabaena bergii

showed the strongest activity, with IC₅₀ values of 4.63 ± 0.21 and 7.23 ± 1.35

µg/mL against HepG2, and 5.24 ± 1.23 and 8.67 ± 1.03 µg/mL against SK-LU-

1, respectively. Aphanizomenon ovalisporum displayed moderate activity

(IC₅₀: 37.51 ± 1.43 µg/mL on HepG2 and 45.92 ± 3.66 µg/mL on SK-LU-1).

Five remaining strains - Microcystis botrys, Microcystis aeruginosa,

Planktothrix zahidii, Planktothricoides raciborskii, and Arthrospira platensis -

showed weak activity, with IC₅₀ values ranging from 58.27 to 97.45 µg/mL.

The two most active strains, Anabaena smithii and Anabaena bergii, warrant

further in vivo investigation to evaluate their efficacy and potential for

developing anticancer agents.