Seaweed Vitamins as Nutraceuticals

Contents I. Introduction 358

II. Importance of Vitamins for Humans 358

A. Function of vitamins in human body 358

B. Vitamin requirements for humans 359

III. Vitamin Composition in Seaweed 360

A. Factors influencing vitamin content in seaweed 360

B. Bioavailability and absorption of vitamins 361

C. Vitamin composition of seaweed 362

D. Antioxidant activity of some vitamins contained in seaweed 364

IV. Conclusions 366 References 366

Abstract Seaweeds are a good source of some water- (fy, B2, B12, C) and fat-

soluble (b-carotene with vitamin A activity, vitamin E) vitamins. To ensure that the adequate intake of all vitamins is received in the diet, people (especially people on special diet, strict vegetarians, and vegans) can consume foods enriched with vitamins, for example, in the form of functional foods with vitamins as nutraceuticals, extracted from natural sources such as seaweeds. Seaweed vitamins are important not only due to their biochemical functions and antioxidant activity but also due to other health benefits such as decreasing of blood pressure (vitamin C), prevention of cardiovascular diseases (b-carotene), or reducing the risk of cancer (vitamins E and C, carotenoids).

Department of Food Analysis and Chemistry, Faculty of Technology, Tomas Bata University in Zlin, Zlin, Czech Republic

1 Corresponding author: Sofia Skrovankova, E-mail address: [email protected]

Advances in Food and Nutrition Research, Volume 64 © 2011 Elsevier Inc.

ISSN 1043-4526, DOI: 10.1016/B978-0-12-387669-0.00028-4 AH rights reserved.

I. INTRODUCTION

Vitamins are organic essential compounds needed in the human body in trace amounts for different chemical and physiological processes. Vitamins are commonly classified into two groups according to their solubility: water-soluble vitamins (members of the vitamin B group and vitamin C) and fat-soluble vitamins (vitamin A and its provitamins—carotenoids with vitamin A activity, vitamins E, D, and K).

Even though vitamins are required only in very small quantities, to ensure that the adequate intake of vitamins in the diet is received, people can consume foods enriched with vitamins, for example, in the form of functional foods with vitamins as nutraceuticals. In addition, certain vitamins extracted from natural sources such as seaweeds have antioxi-dant activity and other health benefits such as decreasing of blood pressure, prevention of cardiovascular diseases, or reducing the risk of cancer.

II. IMPORTANCE OF VITAMINS FOR HUMANS

As mentioned above, vitamins are essential substances which cannot be synthesized by humans or only in limited quantities; therefore, they should be obtained from human diet. Vitamin deficiency can be caused not only by insufficient intake from foodstuffs but also because of increased requirement by certain group of people (people on special diet, smokers), poor absorption, or inadequate utilization.

Seaweeds are generally a good source of some B group vitamins (B1, B2, B12). Other vitamins of B-complex are present too, but only in low or trace amounts (niacin, B6, biotin, folates). Certain seaweeds contain great quantities of vitamins with antioxidant activity, vitamins C and E, and the provitamin forms of vitamin A, carotenoids.

A. Function of vitamins in human body

The hydrosoluble vitamins are needed as enzyme cofactors. The vitamin can have one or a few very specific roles or much more extensive roles. Several B group vitamins serve as coenzymes for enzymes with function in the catabolism of foodstuffs to produce energy for the body. Some of them are fundamental even for their antioxidant activity and other health benefits. Thus low levels of some B group vitamins (B2, B6, B12) can result in reduced levels of DNA methylation and therefore in some kinds of cancer (Hernandez et al., 2003).

The following vitamins are presented in seaweeds in great amounts— thiamin, riboflavin, cobalamin, and ascorbic acid. Thiamin (vitamin B1)

has a key role in the intermediary carbon metabolism and is essential for several enzymes such as pyruvate dehydrogenase, pyruvate decarboxylase, and transketolase. Riboflavin (vitamin B2) is used ubiquitously throughout the cell. Cobalamin (vitamin B12) is required for the activity of cobalamin-dependent biosynthetic enzymes: methionine synthase and methylmalonyl CoAmutase. Interestingly, although vitamin B12 is not found in vascular plants, it is abundant in algae. As only prokaryotes have the ability to synthesize cobalamin, all of the vitamin B12 found in algae must have originally been produced by bacteria (Croft et al., 2006). Ascorbic acid (vitamin C) is fundamental antioxidant in the ascorbate-glutathione pathway. Moreover, it protects enzymes that have prosthetic transition metal ions and is a cofactor of enzymes such as violaxanthin deepoxidase, ascorbate oxidase, and ascorbate peroxidase.

Fat-soluble vitamins, which are present in seaweeds, are vitamin E and provitamins A. Vitamin E (tocopherols and tocotrienols) is important liposoluble antioxidant which is conclusive for the prevention of oxidation of polyunsaturated fatty acids absorbed from the diet. Tocopherols block the production of reactive oxygen species formed during oxidation and help inhibit the low-density lipoprotein (LDL) oxidation as namely oxidatively modified LDL are considered to play a vital role in the development of atherosclerosis (Steinberg, 1991). Vitamin A, retinal, as visual pigments' chromophore, is important in the vision process. Besides the epithelial tissue maintenance and prevention of its keratinization, vitamin A also presents important systematic functions in the growth and reproductive efficiency (Ribeiro et al., 2011). However, plant food such as algae does not contain intrinsic vitamin A, but its provitamins, carotenoids, linear polyenes with a cyclic structure which possesses a p-ring. The most abundant carotenoid with provitamin function in seaweed is p-carotene. It can be cleaved by a p-carotene-15,15'-dioxygenase, resulting in the formation of retinal (DellaPenna and Pogson, 2006; Ribeiro et al., 2011).

B. Vitamin requirements for humans

The recommended daily allowances (RDA) values are based on our knowledge of the minimal requirement for maximal protection for each vitamin-dependent function. Because requirements are not known exactly, these data can differ according to country experts and nutrition organization. Recommendations for some vitamins intake or RDA have been established without taking into consideration their need for enhancing body function and preventing some diseases. Therefore, the intake of vitamins which prevent certain diseases due to its strong antioxidant activity (e.g., prevention of cardiovascular disease and cancer) should be higher than that of RDA values (Weber et al., 1997).

The presented ranges of RDA and median RDA values, from data collected from up to 30 countries, recalculated Brubacher (1989).

RDA for vitamins B1 and B2 are 0.5-2.2 and 0.8-3.2 mg/day, respectively, with the median of 1.2 and 1.6 mg/day. The minimum daily requirement for vitamin B12 is thought to be in the range of ~0.1 mg, the amount of 0.2-0.25 mg absorbed from food is generally adequate, and 1 mg daily would treat people with no stores of vitamin B12, for example, those with vegan diet (Herbert, 1988). According to Brubacher data (1989), RDA value for vitamin B12 is 1-5 mg/day, the median 2 mg/day. The high value of vitamin B12 is presented in red seaweed Porphyra sp. (nori)—33.8 mg/ 100 g dw (Miyamoto et al., 2009). Therefore, a consumption of only 1.5 g of this seaweed would complement the RDA of this vitamin. In result, seaweed can provide an alternative source of this vitamin for strict vegetarians and vegans. However, the bioavailability of different forms of vitamin B12 in seaweeds should be discussed as some introduced results are contradictory. RDA value of vitamin C is 15-100 mg/day, the median 60 mg/day of ascorbic acid.

Concerning the fat-soluble vitamins, the range of RDA value of vitamin E is 5-50 mg of a-tocopherol equivalent per day, the median 10 mg/day. The RDA value of vitamin A is 360-1650 mg/day of retinol equivalent (RE) with the median of 800 RE/day. As mentioned before, seaweed does not contain intrinsic vitamin A, but its provitamins, with p-carotene as the most abundant. The relevant dose of p-carotene intake is about 15 mg/day (Krinsky, 1998). The vitamin A activity (mg RE/100 g) is recalculated from determined content of p-carotene.

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