RODICA SIRBU, GABRIELA STANCIU, ANETA TOMESCU, ANA MARIA IONESCU, EMIN CADAR EVALUATION OF ANTIOXIDANT AND ANTIMICROBIAL ACTIVITY IN RELATION TO TOTAL PHENOLIC CONTENT OF GREEN ALGAE FROM BLACK SEA Worldwide, marine algae are known to produce a wide variety of bioactive secondary metabolites and several compounds have been derived from them for the prospective development of novel drugs by the pharmaceutical industry. In this context, Ulva lactuca, Enteromorpha intestinales, and Cladophora vagabunda, isolated from Black Sea coastal waters of Romania, were evaluated for their potential for bioactivity. Extracts of the algae selected for the study were prepared using ethanol. The study presents original results concerning the total phenolic content (TPC), determined by the spectrometric method (Folin-Ciocalteu method) and the individual phenols from each species of seaweed studied were identified by HPLC-DAD techniques. Total antioxidant activity (ACL) was studied by photochemiluminescence method, and antibacterial activity was studied on two strains of bacteria, Escherichia coli ATCC 10536 - gram-negative and Staphylococcus aureus ATCC 6538P - gram-positive. Results indicated that the highest total phenolic content was obtained for Cladophora vagabunda (325.8 mg/100 g f.w.), followed by Ulva lactuca (285.5 mg/100 g f.w.) and the lowest rate was registered by Enteromorpha intestinalis (268.8 mg/100 g f.w.). Through HPLC-DAD techniques, 6 individual phenolic compounds were identified in all analyzed seaweeds. In addition, two other phenolic compounds were identified in lower concentrations in Ulva lactuca, but only one phenolic compound in Enteromorpha intestinalis. The results of this study show that there is a strong correlation between antioxidant activity (ACL), antibacterial activity and total phenolic content (TPC). Antioxidant activity shows the same order as total phenolic content (TPC): Cladophora vagabunda (64.15 nmol/g sample) followed by Ulva lactuca (22.8 nmol/g sample) and Enteromorpha intestinalis (10.4 nmol/g sample). The antibacterial activity recorded in all green seaweeds shows that the inhibition sites are higher on Escherichia coli compared to Staphylococcus aureus.
Keywords: green seaweeds, antioxidant activity, antibacterial activity, total phenolic content, HPLC-DAD