**1. Introduction**

Antioxidants are attractive as supplements because of their potential preventive role in several diseases associated with oxidative stress, occurring when the balance between antioxidants and reactive oxygen species (ROS) is disrupted because of either depletion of antioxidants or accumulation of ROS [1–3]. There are many in vitro studies allowing speculation in this sense; however, clinical evidences for some of these molecules are weak. For instance, a 2007 systematic review assessed the effect of antioxidant supplements, such as β carotene, vitamins A, E and C, and selenium, on overall mortality in primary or secondary prevention randomized clinical trials. It concluded not only that β carotene and vitamins A and E do not have beneficial effects on mortality, but that they seem to increase the death risk [4]. Indeed, most trials included in this review investigated the effects of supplements administrated in higher doses than those usually found in a balanced diet, and some of the trials used doses well above the recommended daily allowances and even above the upper tolerable intake levels. Furthermore, very heterogeneous populations have been examined in this review and the impact of different types of supplements was evaluated in the general population or in patients with gastrointestinal, cardiovascular, neurological, skin, ocular, renal, endocrinological, rheumatoid, and undefined diseases in a stable phase. However, one possible effective approach for preventing or treating these ROS-mediated disorders is based on a diet rich in natural antioxidants, which is supported by many international health agencies. In this context, there is a growing interest in natural antioxidants as replacements of synthetic compounds because of increased safety concerns and a worldwide trend toward the usage of natural additives in foods [5]. In addition, natural antioxidants derived from various plants and marine algae not only have demonstrated health-promoting benefits, but have also shown a grea<sup>t</sup> potential for improving oxidative stability of food products [6]. Under extreme conditions, di fferent types of edible seaweeds, including *Fucus vesiculosus (F. vesiculosus)*, develop unique metabolic systems to survive leading to the synthesis of a high number of secondary metabolites, most of which are potent antioxidant molecules [7].

Seaweeds are a rich source of nutrients and of di fferent kinds of bioactive substances, including sulphated polysaccharides, such as fucoidans, carotenoid pigments, such as fucoxanthin, and phlorotannins, a subgroup of polyphloroglucinol polyphenols only found in brown seaweeds, with potential health benefits [8]. The antioxidant activity of phlorotannins is closed to phenol rings, which act as electron traps to scavenge ROS. Phlorotannins have been found to possess multiple physiological activities, with anti-carcinogenic, antibacterial, antiviral, anticancer, and anti-inflammatory properties [9–11].

Moreover, polysaccharides, such as fucoidans, are particularly abundant in seaweed, especially in *F. vesiculosus*; they may act as antioxidants by either directly scavenging ROS, or induction of the activity of cellular endogenous antioxidant defenses, including superoxide dismutase (SOD), catalase (CAT), glutathione transferase, and glucose-6-phosphate dehydrogenase [12].

Seaweeds are also a source of dietary fibers, prebiotics, and other functional ingredients that induce a decrease of glucose and cholesterol blood levels [13]. Indeed, seaweed consumption has been related to a lower incidence of chronic diseases, such as dyslipidemia, and coronary heart disease [14,15].

The usage and industrial applications of seaweeds are abundant in Eastern tradition, whereas in Western countries, seaweeds are particularly used for phycocolloids production [16]. Due to their excellent gel properties, the polysaccharide fibers of seaweeds, especially alginic acid, have also been used as stabilizing and water-holding agents. For this reason, seaweeds are very important industrial components in many fields, including cosmetic and pharmaceutical/medical, but also in food industry as thickeners, gels, emulsifiers, and stabilizers. However, since biological activities of seaweeds support their potential role as a natural antioxidant, seaweed extracts and purified compounds may be used as active ingredients to improve oxidative stability of functional foods and nutraceuticals [17].

On the basis of scientific and technological developments since 1997, the Regulation (EU) 2015/2283 of the European Parliament and of the Council reviews, clarifies and updates the categories of food that constitute novel foods. For this Regulation, food consisting of fungi or algae, isolated or produced from microorganisms, are defined as "novel food." Then, although scientific research highlights various bioactivity in seaweed species, marketing it as a novel or functional food with health claims requires scientific evidences, which must be provided by an application submitted to EU, an extensive and time-consuming procedure. In this contest, some *F. vesiculosus* extract or purified molecule are already recognized as Generally Recognized As Safe (GRAS) or novel foods.

Baked foods, such as snacks, cookies, and biscuits, that are consumed and stored for extended periods before consumption, need to preserve their quality to remain competitive on the economic market [18]. To ameliorate shelf life, antioxidants, antimicrobials, and anti-browning additives are mostly used by the food industry [5]. The utilization of synthetic antioxidants has been correlated to possible toxicity and side e ffects, such as carcinogenesis [19], and the use of synthetic antioxidants has declined due to consumer awareness and demand for natural protection. Only a few natural food antioxidants are commercially available on the market. Among these, rosemary extracts have been the most successful natural plant-based antioxidants commercialized [20].

*F. vesiculosus* is a brown algae species whose high antioxidant activity, in addition to other unique properties (e.g., anti-inflammatory and anti-diabetic activities), makes it particularly attractive for its use in various food systems [21]. Due to the strong market demand and very positive preliminary tests, it is believed that its extracts can be highly competitive on the market and find various uses in food.

In this paper, we describe the bioactive properties of *F. vesiculosus* extracts using di fferent chemical and cell-based methods in order to provide evidences of possible antioxidant mechanism(s). Moreover, we present data related to the ability of extracts to increase the antioxidant potential of enriched convenience cereals. This information can be used to define a broad range of categories of convenience food to improve the health of targeted consumers.
