**Evaluation of Ultrasound, Microwave, Ultrasound–Microwave, Hydrothermal and High Pressure Assisted Extraction Technologies for the Recovery of Phytochemicals and Antioxidants from Brown Macroalgae**

**Marco Garcia-Vaquero 1, Rajeev Ravindran 2, Orla Walsh 3, John O'Doherty 1, Amit K. Jaiswal 3, Brijesh K. Tiwari 4 and Gaurav Rajauria 1,2,\***


**Citation:** Garcia-Vaquero, M.; Ravindran, R.; Walsh, O.; O'Doherty, J.; Jaiswal, A.K.; Tiwari, B.K.; Rajauria, G. Evaluation of Ultrasound, Microwave, Ultrasound–Microwave, Hydrothermal and High Pressure Assisted Extraction Technologies for the Recovery of Phytochemicals and Antioxidants from Brown Macroalgae. *Mar. Drugs* **2021**, *19*, 309. https:// doi.org/10.3390/md19060309

Academic Editors: Ipek Kurtboke and Bill J. Baker

Received: 5 May 2021 Accepted: 25 May 2021 Published: 27 May 2021

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**Abstract:** This study aims to explore novel extraction technologies (ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), ultrasound–microwave-assisted extraction (UMAE), hydrothermal-assisted extraction (HAE) and high-pressure-assisted extraction (HPAE)) and extraction time post-treatment (0 and 24 h) for the recovery of phytochemicals and associated antioxidant properties from *Fucus vesiculosus* and *Pelvetia canaliculata*. When using fixed extraction conditions (solvent: 50% ethanol; extraction time: 10 min; algae/solvent ratio: 1/10) for all the novel technologies, UAE generated extracts with the highest phytochemical contents from both macroalgae. The highest yields of compounds extracted from *F. vesiculosus* using UAE were: total phenolic content (445.0 ± 4.6 mg gallic acid equivalents/g), total phlorotannin content (362.9 ± 3.7 mg phloroglucinol equivalents/g), total flavonoid content (286.3 ± 7.8 mg quercetin equivalents/g) and total tannin content (189.1 ± 4.4 mg catechin equivalents/g). In the case of the antioxidant activities, the highest DPPH activities were achieved by UAE and UMAE from both macroalgae, while no clear pattern was recorded in the case of FRAP activities. The highest DPPH scavenging activities (112.5 ± 0.7 mg trolox equivalents/g) and FRAP activities (284.8 ± 2.2 mg trolox equivalents/g) were achieved from *F. vesiculosus*. Following the extraction treatment, an additional storage post-extraction (24 h) did not improvetheyieldsofphytochemicalsorantioxidantpropertiesoftheextracts.

 **Keywords:** seaweed; innovative technology; extraction; polyphenol; nutraceuticals
