Bhaskar Narayan

Physiological Effects of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA)—A Review

Marine lipids have long been documented to be the major source of polyunsaturated fatty acids (PUFAs), especially n-3 fatty acids such as eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (DHA; 22:6 n-3). Both EPA and DHA have been documented to have significant influence on biochemical and physiological changes in the body. Although these long chain PUFA exert positive influences on human nutrition and health, there are also some controversies pertaining to the functioning of these n-3 PUFAs including the extent of their requirement by the body. As marine lipids have been thoroughly reviewed often, the present review mainly focuses on works related to physiological effects of EPA and DHA.

EVALUATION OF RECOVERABLE FUNCTIONAL LIPID COMPONENTS OF SEVERAL BROWN SEAWEEDS (PHAEOPHYTA) FROM JAPAN WITH SPECIAL REFERENCE TO FUCOXANTHIN AND FUCOSTEROL CONTENTS

Fucoxanthin (Fx) and fucosterol (Fs) are characteristic lipid components of brown seaweeds that afford several health benefits to humans. This article describes the quantitative evaluation of lipids of 15 species of brown seaweeds with specific reference to Fx, Fs, and functional long‐chain omega‐6/omega‐3 polyunsaturated fatty acids (PUFAs). In addition, fatty‐acid composition of selected species was also accomplished in the study. Major omega‐3 PUFAs in the brown seaweeds analyzed were α‐linolenic acid (18:3n‐3), octadecatetraenoic acid (18:4n‐3), arachidonic acid (20:4n‐6), and eicosapentaenoic acid (20:5n‐3). Both Fx (mg · g−1 dry weight [dwt]) and Fs (mg · g−1 dwt) were determined to be relatively abundant in Sargassum horneri (Turner) C. Agardh (Fx, 3.7 ± 1.6; Fs, 13.4 ± 4.4) and Cystoseira hakodatensis (Yendo) Fensholt (Fx, 2.4 ± 0.9; Fs, 8.9 ± 2.0), as compared with other brown seaweed species. Studies related to seasonal variation in Fx, Fs, and total lipids of six brown algae [S. horneri, C. hakodatensis, Sargassum fusiforme (Harv.) Setch., Sargassum thunbergii (Mertens ex Roth) Kuntze, Analipus japonicus (Harv.) M. J. Wynne, and Melanosiphon intestinalis (D. A. Saunders) M. J. Wynne] indicated that these functional lipid components reached maximum during the period between January and March. The functional lipid components present in these seaweeds have the potential for application as nutraceuticals and novel functional ingredients after their recovery.

Carotenoid Profile of Edible Japanese Seaweeds: An Improved HPLC Method for Separation of Major Carotenoids

An improved multi-step gradient reverse phase high performance liquid chromatography (HPLC) method to simultaneously separate major carotenoids from natural as well as food samples was developed. Quantitative profiling of carotenoid compounds was carried out on three edible brown seaweeds (Sargassum horneri, Cystoseira hakodatensis, and Undaria pinnatifida) and three red seaweeds (Gracilaria vermiculophylla, Grateloupia asiatica, and Grateloupia livida). Fucoxanthin (Fx) was detected in all the brown seaweeds with quantities (mg g−1 dry weight [dwt]) ranging from 1.3 ± 0.3 in C. hakodatensis to 2.4 ± 0.1 in S. horneri. U. pinnatifida, commonly known as wakame, had a Fx content of 2.3 ± 0.1 mg g−1 dwt. In the case of red seaweeds, zeaxanthin (Zx) was the major carotenoid, and G. vermiculophylla had the highest Zx content (80.2 μg g−1 dwt) among the red seaweeds apart from small amounts of Fx (9.1 μg g−1 dwt). Similarly, the other two species of red seaweeds, G. asiatica and G. livida, contained (μg g−1 dwt) lutein (Lut), Fx, and Zx as the major carotenoids (G. asiatica: Lut 10.4, Fx 1.5, Zx 1.1; G. livida: Lut 9.3, Fx 3.5, Zx 1.0). The results suggest the usefulness of edible varieties (barring wakame) of seaweeds as dietary sources of carotenoids.

Spatial and seasonal variations in the biofunctional lipid substances (fucoxanthin and fucosterol) of the laboratory-grown edible Japanese seaweed (Sargassum horneri Turner) cultured in the open sea

This work studied the effect of spatial and seasonal differences on the accumulation of functional lipid components in Sargassum horneri (Turner), an edible Japanese seaweed popularly called Akamoku. S. horneri obtained from Samenoura bay area of Japan was laboratory cultured to evaluate the effect of temperature on the accumulation of total lipids (TL), fucoxanthin (Fx) and fucosterol (Fs) by the alga. The laboratory cultured 3 month old S. horneri were cultured in the open sea in two different geographical locations off Usujiri and Matsushima to evaluate the monthly variations, over a year, in their TL, Fx and Fs contents. S. horneri grown off the Usujiri area accumulated the maximum TL close to 193 mg g−1 dry weight during the coldest part of the year. Fx and Fs contributed 5.6% and 16.2% of the TL in S. horneri harvested off Usujiri in February. Further, in spite of being the same species and parent stock, S. horneri grown off the Matsushima area accumulated less TL, Fx and Fs as compared to their Usujiri counterparts. Our study clearly indicates the role of temperature and light apart from nutritional profile and depth of waters where the seaweed was grown on the accumulation of functional lipid components in S. horneri.

Chemopreventive Effects of Conjugated Linolenic Acids (CLN) Occurring in Plant Seed Oils

Conjugated fatty acids (CFA) being novel type of biologically functional lipid substances, have received increased interest owing to their beneficial effects on human health. Among CFAs, conjugated linoleic acids (CLA) have been reviewed extensively for their occurrence, health benefits, industrial production and applications. On the contrary, it is worth noting that some plant seeds contain conjugated linolenic acids (CLN) at considerably higher levels (30 to 70 wt% lipid), although other kinds of CFAs including CLA are only found at concentrations less than 1% in natural products. It is thus imperative that CLN are the only CFAs that occur in higher quantities in nature and we have extensively screened CLN from different plant seed oils for their chemopreventive effects. In the ensuing review, we describe in detail the physiological functions of CLN isomers that occur in some plant seeds. CLN from natural origin showed growth inhibitory and apoptotic effects on cancer cells and the activity was dependent on their geometrical/positional structures. All trans CLN exerted stronger growth inhibition and more DNA fragmentation in human colon cancer cells than corresponding CLN isomer with cis configuration. CLN induced apoptosis through decrease of Bcl-2 protein. It will be interacted with increase in PPARγ signaling and up-regulation of gene expression of GADD45 and p53. Enhancement of PPARγ expression was also observed in the rats fed seed oil rich in CLN. Dietary feeding of these CLN-containing seed oil reduced the frequency of colonic aberrant crypt foci (ACF) in rat that is the precursor of colon carcinogenesis in short-term experiment and inhibited the development of colonic adenocarcinoma in long-term experiment.