Marine algae are a well-known source of active compounds with many biological activities. Many studies
had point to the anti-microbial and anti-diabetic activity of seaweeds. Egyptian shores are rich with
seaweeds, yet studies concerning their biological activity are inadequate. In the present work, the 80%
methanolic extract of six seaweeds (Actinotrichia fragilis, Cystoseira myrica, Hormophysa cuneiformis,
Laurencia papillosa, Sargassum cinereum, and Turbinaria turbinate) were tested for their antimicrobial
activity using disc diffusion method and anti-diabetic activity using the Inhibition of α-glucosidase
method. The six species were collected from Hurghada, Red Sea, Egypt during late December, 2012. The
results should that the algal extracts were effective against both Gram-positive and Gram-negative bacteria
when used at 2000μg/disc concentration. On Candida albicuns, both low and high concentrations showed
activity. For anti-diabetic activity, H. cuneiformis was the most active species that reached to 53%
inhibition of α-glucosidase at the highest concentration (1000 μg/ml) with IC50 676.9 μg/ml. In
conclusion, the tested seaweeds possess a good anti-microbial and anti-diabetic activity, especially the
species Hormophysa cuneiformis.