Water-soluble sulfated polysaccharides isolated from two red algae Sphaerococcus coronopifolius (Gigartinales, Sphaerococcaceae) and Boergeseniella thuyoides (Ceramiales, Rhodomelaceae) collected on the coast of Morocco inhibited in vitro replication of the Human Immunodeficiency Virus (HIV) at 12.5 µg/mL. In addition, polysaccharides were capable of inhibiting the in vitro replication of Herpes simplex virus type 1 (HSV-1) on Vero cells values of EC₅₀ of 4.1 and 17.2 µg/mL, respectively. The adsorption step of HSV-1 to the host cell seems to be the specific target for polysaccharide action. While for HIV-1, these results suggest a direct inhibitory effect on HIV-1 replication by controlling the appearance of the new generations of virus and potential virucidal effect. The polysaccharides from S. coronopifolius (PSC) and B. thuyoides (PBT) were composed of galactose, 3,6-anhydrogalactose, uronics acids, sulfate in ratios of 33.1, 11.0, 7.7 and 24.0% (w/w) and 25.4, 16.0, 3.2, 7.6% (w/w), respectively.

Fifty-five aqueous, methanolic, chloroforme-methanolic and dichloromethanolic extracts derived from sixteen species of marine Rhodophyta from the coast of Morocco have been screened for the presence of inhibitory compounds against Herpes simplex virus type 1 (HSV-1) by cell viability method. The aqueous extracts of Asparagopsis armata, Ceramium rubrum, Gelidium pulchellum, Gelidium spinulosum, Halopitys incurvus, Hypnea musciformis, Plocamium cartilagineum,Boergeseniella thuyoides, Pterosiphonia complanata and Sphaerococcus coronopifolius were capable of inhibiting the replication of HSV-1 in vitro at an EC50 (Effective Concentration 50%) ranging from <2.5 to 75.9 µg mL-1. No cytotoxic effect of the aqueous extracts on the Vero cells was observed in the range of the concentrations assayed for all extracts. The results corroborate that marine algae from Morocco can be a rich source of potential antiviral compounds. Keywords: Antiviral, Aqueous extracts, Organic extracts, Rhodophyceae, Herpes simplex virus

The evaluation of the antioxidant activity of ten aqueous and methanol extracts of the red seaweeds, Pterosiphonia complanata, Boergeseniella thuyoides, Sphaerococcus coronopifolius, Asparagopsis armata, Halopitys incurvus, Hypnea musciformis, Gelidium spinulosum, Plocamium cartilagineum, Gelidium pulchellum and Ceramium rubrum was realized through three different tests. Using the DPPH (2,2-diphényl-1-picrylhydrazyl) test, four methanol extracts allowed the transformation of DPPH radical in reduced form with an EC50 between 96 and 862 µg.mL-1. With respect to the β-carotene test, 7 methanol extracts showed activity against peroxide radicals with an EC50 between 9 and 176 µg.mL-1. In the deoxyribose test, the inhibition percentage of hydroxyl radicals varies between 25 and 68% for five aqueous extracts; the most important being the extract of A. armata. Key words: Red algae, antioxidant activity, DPPH, Deoxyribose, β-carotene–linoleic acid system.