Antimicrobial activity of microalgal extracts isolated from Baharia Oasis, Egypt

Abstract

In the present study, the methanolic extract of five species (four cyanobacterial and one green alga)
namely Nostoc caeruleum, Spirulina platensis, Cylindrospermum majus, Oscillatoria formosa and
Chlorella vulgaris were tested with the agar well diffusion method for their antibacterial against three
Gram positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes
) and three Gram negative bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia
coli) as well as for their antifungal activity against (Aspergillus fumigatus, Candida albicans, Geotricum
candidumn and Trichophyton mentagrophytes). The results indicated that the extract of Chlorella
vulgaris was more efficient against the tested bacteria and fungi strains followed by Spirulina platensis.
Chemical analyses showed that Chlorella vulgaris recorded the highest percentages of the total
phenolic and total flavonoid contents. So, C. vulgaris crude extract was tested for their effectiveness as
antioxidant activity. Also, Chlorella vulgaris extract screened for their anticancer activities against
selected cancer cell lines; breast cancer cell lines MCF-7, colon cancer HCT-116 and liver cancer cell
lines HepG-2. The results indicates that the HepG-2 was most sensitive followed by the HCT-116 than
MCF-7 at (IC50) with 40.5, 43 and75.3. µg/ml respectively. Finally the result of GC mass analysis proved
the presence of quercitin compounds.