Bioprospection, study and application of bioactive compounds from microalgae and seaweeds

Microalgae and seaweeds, a natural source of highly valuable bioactive compounds, are considered one of the most promising and innovative sources of novel functional foods that can favourably affect human health. This study focused on the bioprospection of bioactive compounds from freeze-dried biomasses and extracts of selected microalgae (Chlorella vulgaris, Arthrospira platensis, Isochrysis galbana, Tetraselmis IMP3, Tetraselmis CTP4, Skeletonema sp.) and seaweeds (Petalonia binghamiae, Halopteris scoparia, Osmundea pinnatifida, Gelidium sesquipedale, Pterocladiella capillacea) species. The benefits associated with the utilization of these as nutraceuticals or functional ingredients were assessed taking into consideration the nutritional composition, biological activities (antioxidant, anticancer, anti-inflammatory, hypocholesterolemic), and bioaccessibility of target compounds. The bioprospection studied revealed that the microalga I. galbana exhibited the highest phenolic content in both aqueous and ethanolic extracts. The aqueous extracts of the microalgae Skeletonema sp., I. galbana and A. platensis and of the seaweeds P. binghamiae and H. scoparia displayed a strong antioxidant activity (above 90% inhibition). The microalga Skeletonema sp. and seaweeds H. scoparia and P. capillacea ethanolic extracts exhibited high anti-inflammatory potential (above 70% of COX-2 inhibition). Freeze-dried biomass and ethanolic extract of the I. galbana showed to be highly cytotoxic against HeLa human cervical cancer cells, inducing a cell line viability decrease upper 99%, demonstrating anticancer potential. This microalga aqueous extract also presented hypocholesterolemic capacity, inducing a significant decrease of cholesterol absorption through Caco-2 monolayers. I. galbana was also the richest in ω3 long chain polyunsaturated fatty acids (ω3 LC-PUFAs), with high contents of α-linolenic, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Based on I. galbana potential, it was chosen to formulate a high-value functional food by the incorporation of 2% (w/w) of freeze-dried biomass and ethyl acetate lipid extract, as value-added food ingredients in the yogurts’ preparation, in order to increase and improve the bioaccessibility of lipids. When comparing to the original yogurt, the obtained results showed an increasing of ω3 LC-PUFAs level, specially of DHA, and ω3/ω6 ratio reached a more desirable level. The bioaccessibility study using in vitro digestion model showed a poor bioaccessibility of ω3 LC-PUFAs. The obtained results pave the way for future application of these algae species for pharmaceutical, nutraceutical and food industries