There is evidence that small peptides, ranging in size from 2 to 20 amino acid residues, have revealed promising antihypertensive properties, and this type of peptides can be obtained from seaweed protein hydrolysates [35].

Macroalgae protein-derived bioactive peptides possess several beneficial pharmacological properties; among them, the ability to act as antihypertensive agents [29]. Peptides are the most commonly studied natural compounds that inhibit ACE I activity, even the ones isolated from other sources than macroalgae [10,30,31]

Most macroalgae products described in the scientific literature as having antihypertensive and/or anti-obesity effects are the whole extract (aqueous or alcoholic), or fractions rich in a particular type of compound (e.g., fucoidans, alginates, phlorotannins) [22,23,26,27].

The pathogenesis of hypertension is multifactorial and complex, being related to differing concentrations of sodium and potassium in the body, obesity, insulin resistance, high alcohol intake, low calcium intake, stress and ageing diseases. The three main factors that determine blood pressure are renal sodium excretion (and the resultant impact on plasma and total body volume), vascular tone and cardiac performance and these factors control the cardiac output, the intravascular volume and the systemic vascular resistance [3,6].

Seaweeds, in addition to their use as food, are now unanimously acknowledged as an invaluable source of new natural products that may hold noteworthy leads for future drug discovery and development, including in the prevention and/or treatment of the cardiovascular risk factors. Several compounds including peptides, phlorotannins, polysaccharides, carotenoids, and sterols, isolated from brown, red and green macroalgae exhibit significant anti-hypertensive and anti-obesity properties.

Abstract: The present study is focused to evaluate the effect of three different brown seaweeds on blood pressure and heart rate (HR) using spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats.  The seaweeds, Turbinaria ornata (T. ornata), Sargassum species (Sargassum sp.) and Padina tetrastromatica (P. tetrastromatica), were extracted in cold water and freeze-dried. Anaesthetised rats were prepared for direct blood pressure measurements with the changes in HR also being monitored. Rats were administered intravenously with the aqueous extract of the seaweeds at doses of 2.5 to 20.0 mg/kg.  Concentrations of Na+, K+, Ca2+ and Mg2+ found in the dose of 20.0 mg/kg of the marine plant extracts were determined. Subsequently, salt solutions containing the equivalent cationic concentration found in each of the seaweed extracts were tested on Sprague-Dawley (SD) rats. All seaweeds investigated produced significant (P < 0.05) reductions in the blood pressure of both SHR and the control WKY rats. In T. ornata, significant (P < 0.05) HR reducing effect was produced. In contrast, this effect was not seen in other brown seaweeds tested. Analysis of the ionic composition present in all the extracts revealed that the salt solution with equivalent ionic content of each seaweed extract did not produce any significant decrease in blood pressure of the SD rats. In conclusion, the data obtained from the present study suggest that the aqueous extracts of T. ornata, Sargassum sp. and P. tetrastromatica may contain blood pressure lowering agents. 

Light exhibits certain behaviors that are characteristic of any wave and would be difficult to explain with a purely particle-view. Light reflects in the same manner that any wave would reflect. Light refracts in the same manner that any wave would refract. Light diffracts in the same manner that any wave would diffract. Light undergoes interference in the same manner that any wave would interfere. And light exhibits the Doppler effect just as any wave would exhibit the Doppler effect. Light behaves in a way that is consistent with our conceptual and mathematical understanding of waves. Since light behaves like a wave, one would have good reason to believe that it might be a wave.

go beyond the limitations of our eyes, we build telescopes and detectors that help us expand our physical perceptions. Some of these are the familiar visible-light telescopes seen at mountain-top observatories; they allow us to see fainter objects with more detail than our eyes alone could see. We also use sophisticated radio antennas and receivers—radio telescopes. In fact, there are different telescopes for all of the types of light in the electromagnetic spectrum: radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma-rays. Each kind of light has a different amount of energy and interacts differently with matter. By looking at what happens to light when it is emitted or absorbed by various types of objects, or when the light emitter is moving through space, we can determine important physical properties of astronomical objects, such as temperature, density, and chemical composition.