Preliminary Studies on the Iodine Content of some Marine Algae from Coastal Areas of Jaffna Peninsula

The iodine content of twenty seven species of marine algae collected from different coastal regions of the Jaffna Peninsula was determined. Of the species analysed, Gracilaria opuntia (1277 ppm), Gracilaria crassa (889 ppm) and Turbinaria ornata (810 ppm) have relatively high iodine contents. The iodine content of Gracilaria opuntia is comparable with the amount of iodine present in caliche deposits (1500 ppm) in northern Chile which is the principal source of iodine.


Introduction
Iodine is considered9 as one of the essential elements for the proper functioning of the hormones of human and animal thyroid glands.In many parts of the world simple goitre develops because of deficiency of iodine in water or food supply.An iodine deficient goitrous mother may give birth to a cretinous baby9 because the foetus requires an adequate secretion of thyroxine during the later stages of pregnancy.Thyroxine is formed9 by the reaction of tyrosine with iodine.
To prevent simple goitre a dietary iodine intake of 100 -200 P g daily9 is required.In places where manioc is used as a part of the diet the daily intake of iodine should be greater than the normal requirement.It is believed that cyanide in the manioc is converted to thiocyanate in the body which apparently displaces iodide from the reaction site.All iodine is converted to iodide in the gut.@Normally iodine is supplied from water.
In some places iodine content of water may not be enough to meet daily requirement of iodine.Seaweeds are good sources to meet dietary requirements of iodine.Goitre disease caused by iodine deficiency is less prevalent in countries where marine algae form a part of the diet.l,p The iodine has wide and varied uses and is of high demand.Attempts are being made by various workers and companies to extract iodine from various natural sources.Caliche deposits in northern Chile are the principal sources for the production of iodine.1In Japan, Norway, France and Russia, iodine is extracted in small amounts from seaweeds.6,8Valuable data on the iodine content of' marine algae occurring in different parts of the world are available.s,5But infor-mation on the iodine contents of the species of algae from Sri Lankan coastal area d P is not available.Therefore as an initial study, the amounts of iodine present in twenty seven species of green, brown and red algae collected from Jaffna coastal areas were estimated.

Experimental Methods and Materials
The localities and habitats of the algae studied are given in Table 1.The freshly collected seaweed samples were washed free from extraneous matter and air dried at room temperature under fans.The air dried samples (30 -50 g), weighed accurately, were dried in an oven at 110°C to constant weight and the moisture contents determined.The oven dried samples were ground and the iodine contents were estimated by the alcoholic potash method2 as follows: Accurately weighed powdered samples (5 -10 g) were refluxed with alcoholic potash (lo%, 30 -60 ml) for 24 hours, evaporated and ashed at 5OO"C.The water extract of the ash was acidified, oxidised with bromide and titrated with standard sodium-thiosulphate.

Results and Discussion
The results of analysis (carried out in triplicate) are given in Table 2.This table also gives the corresponding values for unwashed samples for a few species.
The above results show that of those species investigated, Gracilaria opuntiu, Gracilaria crassa and Turbinaria ornata have reasonable amounts of iodine.To prevent simple goitre a dietary iodine intake of 100 -200)1 g daily is sufficient.Therefore a vegetarian can easily get the required amount of iodine from properly processed marine algae.
The most important natural source, caliche deposits, found in Northern Chile which exports iodine to all parts of the world contains 0.15% (1500 ppm) of iodinel, Gracilaria opuntia has comparable amount of iodine (1277 ppm), Gracilariu crassa (889 ppm) and Turbinaria ornata (810 ppm) also have fairly large amounts of iodine.These three species would prove to be of commercial value.
Out of the three areas investigated marine algae from Mandaitivu coastal area have more iodine.It is significant that the sea water from this area has more iodine compared to the other two areas (Table 3).The iodine contents of Ulva lactuca, Codium species and Sargassum species are nearly the same as those reported3 for the same species from the Gujarat coast of India (Table 4).

Conclusion
The amount of iodine present in certain species (e.g.Gracilaria opuntia, Gracilaria crassa, Turbinaria ornata) of marine algae from coastal areas in the Jaffna Peninsula is comparable with the most important natural source, caliche deposits.These seaweeds could be exploited for the commercial extraction of iodine.Several other species have reasonable amounts of iodine and these could be used in the manufacture of fortified cattle teed and for preparation of high iodine food items for human consumption.

TABLE 2 .
Algce TABU 1. Localities and Habitats of the algae Iodine contents of Marine Algae

TABLE 3 .
Iodine content in sea-water samples

TABLE 4 .
Iodine contents reported8 of some algae from the Gujarat coast of India