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. 2013 Oct 4:13:255.
doi: 10.1186/1472-6882-13-255.

Biological properties of carotenoids extracted from Halobacterium halobium isolated from a Tunisian solar saltern

Molka Abbes  1 , Houda Baati, Sonda Guermazi, Concetta Messina, Andrea Santulli, Neji Gharsallah, Emna Ammar
Affiliations

Biological properties of carotenoids extracted from Halobacterium halobium isolated from a Tunisian solar saltern

Molka Abbes et al. BMC Complement Altern Med. .

Abstract

Background: Bioactive molecules have received increasing attention due to their nutraceutical attributes and anticancer, antioxidant, antiproliferative and apoptosis-inducing properties. This study aimed to investigate the biological properties of carotenoids extracted from Archaea.

Methods: Halophilic Archaea strains were isolated from the brine of a local crystallizer pond (TS7) of a solar saltern at Sfax, Tunisia. The most carotenoid-producing strain (M8) was investigated on heptoma cell line (HepG2), and its viability was assessed by the MTT-test. The cells were incubated with different sub-lethal extract rates, with carotenoid concentrations ranging from 0.2 to 1.5 μM. Antioxidant activity was evaluated through exposing the cells to sub-lethal extract concentrations for 24 hours and then to oxidative stress induced by 60 μM arachidonic acid and 50 μM H₂O₂.

Results: Compared to non-treated cells, bacterial carotenoid extracts inhibited HepG2 cell viability (50%). A time and dose effect was observed, with cell viability undergoing a significant (P < 0.05) decrease with extract concentration. After exposure to oxidative stress, control cells underwent a significant (P < 0.05) decrease in viability as compared to the non-treated cells.

Conclusions: The bacterial extracts under investigation were noted to exhibit the strongest free radical scavenging activity with high carotenoid concentrations. The carotenoid extract also showed significant antiproliferative activity against HepG2 human cancer cell lines.

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Figures

Figure 1
Figure 1
Structure of bacterioruberin (A) and lycopene (B) pigment [13].
Figure 2
Figure 2
Absorbance spectrum of Halobacterium halobium M8.
Figure 3
Figure 3
Phylogenetic tree of the M8 strain. Phylogenetic relationships between the M8 strain 16S rRNA sequences and other related archaeal sequences previously published in the databases. The phylogenetic tree was built by Neighbour-joining method using the ARB software package. The scale bar corresponds to a 10% estimated difference in nucleotide sequence positions. Methanosarcina mazei (X69874) was used as an outgroup.
Figure 4
Figure 4
Morphological changes of Hep-G2 cells treated with the bacterial extract. The cells (104 cells/well) were incubated in the presence of medium alone (A) and CE (0.2-0.5 μM) (B) for 48 h. Morphological changes were observed by microscopy (x50).
Figure 5
Figure 5
Effect of carotenoid extract in HepG2 cells on cell viability: co: Control; CE: carotenoids extract, 1 : 0.2 μM, 2 : 0.5 μM, 3 : 1.5 μM.
Figure 6
Figure 6
HepG2 cell viability after exposure to carotenoids extract and oxidative stress with arachidonic acid (AA).
Figure 7
Figure 7
HepG2 cell viability exposed to carotenoids extract and oxidative stress with hydrogen peroxide (H2O2).
See this image and copyright information in PMC

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