Pressurized liquid extraction of bioactive extracts with antioxidant and antibacterial activity from green, red and brown Algerian algae

In this work, the protein, sugar, phenolic and phlorotannin contents, as well as the antioxidant and antibacterial activity of hydroethanolic extracts of six algae species from the west cost of Algeria (Padina pavonica, Halopteris scoparia, Cystoseira mediterranea, Ulva lactuca, Ulva intestinalis, and Ceramium virgatum), obtained by pressurized liquid extraction (PLE) were investigated. Ceramium virgatum PLE extracts showed the highest content of protein (4.36 ± 0.13 %), while the total sugar content was maximum in U. lactuca extract (23.89 ± 0.21 %). Likewise, P. pavonica PLE extract presented a relevant total phenolic content (49.82 ± 1.40 mg GAE/g extract). On the other hand, phlorotannins were only found in brown algae in a range of 1.84–2.93 mg PGE/g. Furthermore, P. Pavonica extract presented considerably higher antioxidant capacity of inhibiting ABTS radical (1.16 ± 0.023 mmol TE/g) and 50 % of DPPH (1,1-diphenyl-2-picryl hydrazyl) (IC₅₀ = 57.03 ± 1.28 μg/mL) in comparison with the other studied algae. Regarding to the potential antimicrobial activity, the results showed that Cystoseira Mediterranea produced the lowest minimal inhibitory concentration on Salmonella typhi (0.83 ± 0.14 mg/mL), Escherichia coli (4.66 ± 0.57 mg/mL), Vibrio cholera (1.08 ± 0.14 mg/mL), and Candida albicans (2.16 ± 0.28 mg/mL). Besides, different carotenoids and phenolic compounds were tentatively identified by LC-DAD in the algae extracts which could be the responsible of the tested bioactivities. These findings show the potential of using PLE as green solvent extraction technique and the prolific bioactivities of Algerian seaweeds.