Value of selected Azorean macroalgae as a rich source of macroelements and comparison with some common foods

Marine macroalgae have been described as a great natural source of the minerals and, according to Ortega-Calvo et al. [1], its content is high relatively to the most common vegetables. They have the capacity to accumulate minerals according to environmental conditions and it is also well known that macroalgae chemical compositions differ according to the species, their geographic origin and their seasonal conditions.

The Archipelago of the Azores has a long tradition in the use of marine macroalgae as fertilizers for local agriculture and has a limited use as a food supplement. Being isolated in the middle of the Atlantic Ocean and taking into account the low pollution levels of its seawater [2], the Azores Islands have become a very promising location as a natural resource for marine organisms which may produce new ingredients of so-called functional or health-promoting foods. The objective of this study was to evaluate the macroelements composition of six macroalgae from Azorean S. Miguel Island shores.The minerals content was determined by ionic chromatography, using the universal cation exchange column, and significant differences in the amount of Na, K, Mg, Ca and Na/K ratio are shown in Table 1. Ulva rigida and Ulva compressa show a superior content of Mg as compared with the others algae and also all Azorean macroalgae referred in this study presents significant values for K. The minerals contents revealed to be higher than that in some common foods [3]. In addition, the Na/K ratio of all macroalgae in this study shows a low value specially the Gelidium microdon (0.35) and Pterocladiella capillacea (0.27). In contrast, sausages and olives have Na/K ratios of 4.89 and 45.63, respectively [1]. It is well known that food intakes with high Na/K ratio have been related to the higher incidence of hypertension. Marine algae can, therefore, help balance high Na/K ratio diets.

Tab. 1: Composition of minerals (mg/100 g of dry weight) in macroalgae.

	Macroalgae/Foods	Na	K	Mg	Ca	Na/K
Chlorophyta	Ulva compressa	1322.49 ± 3.17	693.32 ± 2.27	1594.12 ± 3.11	242.57 ± 1.15	1.91
	Ulva rigida	576.08 ± 2.34	817.46 ± 3.81	1775.13 ± 4.74	324.93 ± 1.94	0.70
Rhodophyta	Gelidium microdon	433.08 ± 2.60	1238.98 ± 3.00	127.01 ± 0.39	74.73 ± 0.15	0.35
	Pterocladiella capillacea	635.62 ± 3.26	2359.32 ± 10.45	152.72 ± 1.25	174.00 ± 1.45	0.27
Ochrophyta	Cystoseira humilis	2121.03 ± 7.38	3119.78 ± 12.55	376.12 ± 2.20	253.40 ± 1.30	0.68
	Sargassum cymosum	1725.38 ± 5.05	2967.31 ± 8.26	338.11 ± 1.46	142.65 ± 0.97	0.58
Foods	Brown rice*	28.0	1160.0	520.0	110.0	0.024
	Whole milk*	55.0	140.0	11.0	115.0	0.39
	Cheddar cheese*	670.0	77.0	25.0	720.0	8.70
	Bananas*	1.0	400	340.0	6.0	0.003
Values are expressed as mean ± SD (n = 3). *Values for whole foods from McCance et al. [3] in mg/100 g of dry weight.

Keywords: macroalgae, macroelements, ionic chromatography, health-promoting foods

References:

[1] Ortega-Calvo, J.J. et al. (1993)J Appl Phycol 5:425 – 435.

[2] Neto, A.I. et al. Qualidade de águas costeiras do Grupo Oriental do arquipélago dos Açores e proposta de monitorização. Departamento de Biologia: Universidade dos Açores; 2009.

[3] McCance, R.A. et al. Composition of Foods, 6th edition. Cambridge: Royal Society of Chemistry; 1993.