Recovery of phenolic compounds of food concern from Arthrospira platensis by green extraction techniques

Arthrospira platensis UTEX 1926 has attracted attention because of its ability to produce high value-added compounds such as polyphenols, but their profitable recovery is recognized as a big challenge. In this study, different green extraction techniques, namely ultrasound-assisted (UAE), microwave-assisted (MAE) and high pressure/temperature (HPTE) extractions were compared with classic solid-liquid extraction (SLE) in terms of phenolic compounds recovery from A. platensis using ethanol as solvent and antiradical power (ARP). HPTE proved the most efficient extraction method, allowing maximum total polyphenol yield (TP) of 3.32 +/- 0.08 mg of gallic acid equivalent [GAE] per gram of dry biomass [DB] and ARP of 58.30 +/- 0.12 mu molTrolox g(DB)(-1), whereas maximum total flavonoid yield (TF) was 2.80 +/- 0.18 mg of catechin equivalent [CE] g(DB)(-1) in MAE extract. Once HPTE had been selected as the best-performing extraction method, a 3(2)-full factorial design was applied to evaluate the combined effects of temperature (90 <= T <= 180 degrees C) and ethanol concentration in water (20 <= Sc <= 100% v/v) on TP, TF and ARP by Response Surface Methodology (RSM). RSM revealed that the most suitable conditions for TP (26.00-28.04 mgGAE g(DB)(-1)) and TF (10.25 +/- 0.34 mgCE g(DB)(-1)) were T = 180 degrees C and 20 <= Sc <= 60% (v/v), while ARP was maximized (67.77-69.02 mu molTrolox g(DB)(-1)) at 90 <= T <= 135 degrees C. HPLC analysis showed that catechin, vanillic, gallic and syringic acids were present in very low concentrations (up to 0.05 +/- 0.01 mg 100 g(DB)(-1)) in MAE, UAE and SLE extracts, while they were the most abundant phenolics in HPTE (3.45-3.61, 1.06-2.02, 1.64-1.71 and 0.99-1.26 mg 100 g(DB)(-1), respectively). These compounds taken together effectively contributed to both TP (r = 0.928) and TF (r = 0.960), but not to ARP. This work opens new perspectives for HPTE use as emerging technique to obtain high-ARP phenolic-rich hydroalcoholic extracts of A. platensis, which may serve as a natural source of compounds to formulate functional foods or prepare dietary supplements.