QUALITATIVE ASSESSMENT OF THE FATTY ACID COMPOSITION OF EDIBLE SEAWEEDS FROM COASTAL AREAS OF MANILA BAY AND ROXAS CITY, PHILIPPINES

Nancy Lazaro-Llanos and Sean Mikhail B. Dalawampu. Chemistry Department, De La Salle University-Manila, 2401 Taft Ave. Manila 1004, Philippines. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

This study aimed to come up with a qualitative profile of the fatty acid composition of some of the most abundant seaweeds in the Philippines. Lipid extraction on the freeze-dried samples was done using a modified version of Bligh & Dyer. The lipid extracts were derivatized into fatty acid methyl esters using based-catalyzed transesterification via methanolic potassium hydroxide solution and analyzed using gas chromatography mass spectrometry. Results revealed the presence of the following omega-3 fatty acids: linoleic, eicosatrienoic, and eicosapentaenoic.
In addition polyunsaturated omega-6 and monosaunsaturated C18 fatty acids (oleic and eladic acid) have also been detected. This investigation has demonstrated the potential of edible seaweed as a significant source of omega-3 and other essential fatty acids.

…………………………………………………………………………………………………….... Introduction:-
Seaweeds or marine macro-algae, have found a wide variety of applications. It is used as a constituent in pharmaceutical and personal care products; as fertilizers; as feed for livestock, as filtering agent in wastewater treatment; and as gelling agent, stabilizer, or emulsifier. Above all, the most popular use of seaweeds is as an ingredient in various exotic dishes like salads and soups. Seaweeds, widely accepted as health food, have been found to be rich in vitamins and minerals, proteins, fiber, phytochemicals, and have exhibited antibacterial and antioxidant properties (

Materials and Methods:-
Seaweeds were gathered in June (Batch 1) and October (Batch 2). There were two areas of collection: Manila Bay in Luzon (Caulerpa racemosa Forskl. J.Ag. and Gracilaria tenuistipitata) and Roxas City in Central Philippines (Caulerpa racemosa Forskl. J.Ag.and Hynea nidulans Setchell). The samples were washed repeatedly with tap water and three times with distilled water, freeze-dried, grounded, and stored at -20ºC.
A modified version of Bligh & Dyer method (1959) was used to extract the lipids from the freeze-dried samples. Exactly 2 grams of each sample was successively soaked in the following solvents: methanol, 1:1 methanol:chloroform, and chloroform. After each addition, the mixture is stirred for two minutes and filtered. The filtrates were collected, pooled, and transferred to a separatory funnel. An equal volume of water was added and the mixture was allowed to stand for about three hours. The denser chloroform layer was collected, dried using anhydrous sodium sulphate, and concentrated under vacuum. The crude extract was re-dissolved in 2 mL hexane.
A 2.0 mL of 2M methanolic potassium hydroxide solution was added to each sample. The test tube containing the reaction mixture was covered by a rubber stopper and mixed for 1 minute using a vortex mixer. Afterwards, the upper hexane layer was collected using a glass syringe. Extracts were filtered into its respective glass vials using a Whattman filter, and then subjected to GC-MS analysis GCMS model used was the Agilent Technologies 7890A GC System and 5977A MS System using two parameters. The first parameter was designed for optimizing peaks for EPA and DHA. For this method, total run time was set to 35 minutes with an injection volume of 1 μL. Initial temperature was set to 80⁰C with an increase of 10⁰C per minute until 300⁰C was reached. The second parameter was designed to optimize peaks relating to ALA. The total run time was set to 58 mins. with an injection volume 1 μL. Initial temperature was set to 80⁰C with an increase of 10⁰C per minute until 300⁰C was reached. Each run was done in duplicate.

Identification of Seaweeds:-
The seaweeds were identified and authenticated by the Botany Division of the Philippine National Museum. Table 1 shows the qualitative profile of the saturated fatty acid composition. Results demonstrate that C12-18 saturated fatty acids are present in all the samples regardless of the time and the place of collection. The difference is seen for C20 and above. The presence of C20 and above saturated fatty acids was noted in the green algae C. racemosa and very little up to none in the two red algae samples.  The polyunsaturated fatty acid (PUFA) composition is shown in Table 3. Omega-3 fatty acids ALA, ETA, and EPA were demonstrated to be present in all samples but not DHA. Results also reveal presence of several omega-6 fatty acids, among them are linoleic acid, an essential fatty acid that is incorporated in biological membranes; and arachidonic acid, the precursor of eicosanoids such as prostaglandins, leukotrienes, and thromboxanes.  Generally, data indicated the presence of polyunsaturated C12-C18 in most of the samples with variations when it comes to C20 or higher. In this study, saturated fatty acids C20 -C24 were detected in the green algae C. racemosa. However they were not observed in G. tenuistiptata and once only in H nidulans, both classified as red algae. The presence of elaidic acid, a trans fatty acid, have also been shown in studies by J. Ortiz (2006). Oleic acid is a naturally occurring fatty acid. On the other hand elaidic, a trans fat, is implicated in the lowering of HDL and increasing LDL levels (Abbey and Nestel 1994). Erucic acid, a fatty acid found in rapeseed, mustard seed, and sunflower seed, was not detected. The presence of erucic diet is a health concern (Food and Standards Australia 2419 New Zealand 2003) since studies have shown that high amounts erucic acid in the diet of laboratory rats led to the development of myocardial lipidosis and heart lesions (Chariton et al. 1975). There were some differences in the lipid composition in the June and October collection and such is consistent with studies done by Khairy & El-Shafay (2013) and Nelson et al. (2002).

Results:-
Omega-3 fatty acids ALA, ETA, and EPA were found to be present in all the samples. However the presence of DHA was not detected. Dawczynski

Conclusion:-
This study has confirmed the presence of essential fatty acids including omega-3 fatty acids in common seaweeds in the Philippines used for both human and animal consumption. These edible seaweeds, with its high nutritional value, can definitely be healthy alternative to the usual meal. However like other food products, possible risks of daily consumption should be evaluated.