Evaluation of the Biological Activities of Two Macro-Algae Collected from the Red Sea of Jeddah

Marine algae were used in many biological applications. Two marine algal samples, Halimeda tuna and Dictyota dichotoma, were collected from Obhur region, Jeddah, Saudi Arabia, washed with water, dried and extracted with methanol. The antimicrobial activities were conducted against some pathogenic bacteria. The results showed that the extracts of both Halimeda tuna and Dictyota dichotoma were active against at least one of the tested organisms. The highest antimicrobial activities of the extracts Halimeda tuna and Dictyota dichotoma were against Staphylococcus aureus and Streptococcus pneumonia. On contrast, both Halimeda tuna and Dictyota dichotoma showed weak inhibition against Pseudomonas aeruginosa and Acinetobacter baumannii. Moreover, the mixture of the two algal extracts showed excellent inhibition for all the tested bacteria. In addition, a toxicological experiment was conducted for the two algal extracts using Artemia salina as test organism. No toxicity was found for the two tested methanolic extracts. Furthermore, moderate antitumor activity was recorded for the two tested algal extracts against two cell lines, MCF-7 (breast cancer) and HepG2 (hepatocellular carcinoma) using in vitro MTT and Neutral Red assays. Also, the chemical analysis of each algal extract was carried out. In conclusion, these algal extracts inhibited some pathogenic microbes and can be used as antimicrobial agents. In conclusion, the two collected macro- algae showed antibacterial activities specially against Salmonella which contaminate food, thus the powder or the extracts of these two algae can be used safely as food additive