The report, titled “Overview on the Antihypertensive and Anti-Obesity Effects of Secondary Metabolites from Seaweeds,” cites more than 100 studies. It was published in the July edition of the journal Marine Drugs.
The cited research covered a plethora of edible seaweed species in the red (Rhodophyta), green (Chlorophyta) and brown (Phaeophyta) macroalgae classifications.
“Seaweeds, also known as macroalgae, are traditionally used as food, mainly in China, Japan and the Republic of Korea, and they have recently become a popular ingredient in some Western diets. Some facts contribute to their success as food, for example the association between seaweed dietary intake and longer life expectancy or lower incidence of certain diseases, such as cardiovascular disease,” the authors noted.
Alternative to ACE 1 inhibitor drugs
ACE 1 inhibitors are an ubiquitous family of drugs. Suppressing the action of this enzyme is a common and time-tested strategy for dealing with hypertension, but can come at a cost, including a dry cough and the swelling of certain tissues, including in the throat. Because of these issues, more recently the inhibition of renin, the initial rate-limiting enzyme in the Renin-Angiotensis System (RAS), has become a target, the authors noted.
Some macroalgae derived compounds can play a role here, both in offering side-effect free ACE 1 inhibition as well as having an effect on RAS, the authors said. These include a number of peptides that can be found in the species Undaria pinnatifida and Pyropia yezoensis. The most promising peptides mentioned are designated as IY and AKYSY.
In addition, the authors noted that various phlorotannins and polysaccharides that can be found in macroalgae have intriguing anti hypertensive properties. Among the phlorotannins, the authors noted that dieckol, 6,6′-bieckol and phlorofucofuroeckol A showed promising properties.
Among the polysaccharides, D-Polymannuronic sulphate, a carbohydrate type compound that can be obtained from the brown alga Pelvetia canaliculata, was a promising molecule.
Among the compounds showing anti obesity effects, the authors noted that the carotenoid fucoxanthin is the star.
“Fucoxanthin is probably the most recognized secondary metabolite found in macroalgae, and its biological properties are well established. Among all activities, the anti-obesity is almost certainly the most studied one,” they noted.
But certain phlorotannins showed anti-obesity potential as well, the authors noted, especially in the area of adipose differentiation, basically the process by which precursor cells become fully formed fat tissue.
One study they cited indicated that the lower molecular weight of the phlorotannic compound, the greater the potential on adipose differentiation, with the phlorotannins with phloroglucinol, dioxinodehydroeckol, and eckol dervied from the edible brown alga Ecklonia stolonifera showing the greatest activity.
More in vivo research needed
The authors concluded that these compounds show great potential, but as much of the cited research was done in vitro, more in vivo data is called for.
“It is obvious that pure secondary metabolites from seaweeds represent promising anti-hypertensive and anti-obesity agents with considerably high activities (IC50 values in the micromolar range), through the counteracting of key mechanisms underlying the onset of such disorders. The most active ACE inhibitors reported are the peptides IY and AKYSY (IC50 1.52–2.96 μM) while the best phlorotannin with ACE I inhibitor activity reported is phlorofucofuroeckol A(IC50 12.74 μM). Compounds that act in other antihypertensive targets, such as RAS system or nitric oxide synthase activators, were also reported however, in our opinion, their real pharmacological potential needs to be confirmed,” they said.
“Only a few in vivo studies were published, which is indicative that more research using in vivo models is required.
“Fucoxanthin seems to be the most studied and promising anti-obesity compound, while the 6,6′-bieckol seems to be the most interesting phlorotannin since it is able to strongly suppress the lipid accumulation in 3T3-L1 adipocytes,” the authors said.
Supplements seen as candidate delivery mode
While the journal this review was published in trends toward drug discovery, the authors said the near term target for these compounds is probably most likely in dietary supplements.
“Given that many of the algae in which antihypertensive and anti-obesity compounds have already been identified are edible algae, it will be anticipated that, at an early stage, the benefits of these compounds will be from functional foods and only later as drugs,” they said.
Source: Marine Drugs
2018, 16(7), 237; doi:10.3390/md16070237
Overview on the Antihypertensive and Anti-Obesity Effects of Secondary Metabolites from Seaweeds
Authors: Seca AML, Pinto DGCA