JOHN J. LAL
Centre for Development of Science and Technology, Mannuthy P O,
PB No. 23, Thrissur, Kerala, India, PIN 680 651.
ABSTRACT
Cycas revoluta is popularly known as �King Sago� is one of the useful trees in the world and is not a real palm but a cycad. Cycads, the most primitive of the living gymnosperms, have been used for food and medicinal purposes by many cultures. The term sago means an edible starch extracted from the pith like center of several Asian palms or sometimes of cycads. The stem, root and seed of the King Sago yield an edible �sago� which is a staple food for the poor natives. It plays an important role in the religious and cultural activities of the local populations. It has medicinal as well as toxic properties and thus plays an important role in the health of the consumers. The nutritional aspect of the Sago palm is mainly centered on its stem and seeds. There are some toxic principles in this plant which includes a glycoside, cycasin and an amino acid B-methylamino-L-alanine (BMAA) present in the starch. Natives are aware about these toxins and they have different techniques for the removal of these toxins.
It is one of the cheapest and most readily available sources of food starch. It is a native of China and Japan but widely grown as an ornamental plant in India. In combination with protein from sources such as fish and nuts, and vitamins from wild fruits, it forms a diet that has nourished communities in underdeveloped regions for many centuries. Even today it is a major energy food for many poor populations and is also a valuable famine food in these regions. The Japanese show special affinity for this plant and it plays an intimate role in Japanese culture. The genus also occurs in the Malaysian region and South East Asia, extending to Micronesia, Polynesia, Madagascar and East Africa and constitute one of the oldest living plants on the earth. It plays an important role in the life of the locals as a source of cheap food in the form of �Sago� and also plays a negative role by producing some toxins. These toxins are very strong and found in most parts of the plant. Consumption of the parts of the plant or even the processed flour from the plant has been implicated in a number of disease conditions.
This attractive, ornamental tree is about two meters in height and has branched stems with multi heads. The plants grow in xerophytic areas like exposed slopes and other sunny places where water is scarce. It is hardy to -90C F and can also withstand high temperatures. It has a tuberous stem at young age and rough, thick columnar stem in adult stage and it is covered with an armour of thick persistent leaf bases and at the apex with a crown of large compound leaves in apparent whorls. Once or twice in a year, they produce a complete circle of new leaves emerging all at once. The main rachis of the young leaves is incurled and the leaflets are inrolled as in ferns. The general appearance of the plant is similar to that of a small palm and is popularly known as �cocopalm� by the natives.
Internally the stem consists of an outer protective layer: the epidermis, large parenchymatous cortex and large pith containing thin walled cells densely filled with starch or sago grains, numerous mucilage canals and vascular bundles. Sago, the edible starch that could be extracted from the stem of cycads.
There are two types of leaves: the scale leaves and foliage leaves. They are arranged in close spiral succession alternating with each other. The scale leaves are brown, persistent, numerous than foliage leaves and play a protective role. The foliage leaves are large, 60 cm long, compound and pinnately divided into more than one hundred leaflets with a revolute margin, thus giving the plant its specific name (Cycas revoluta). The mid rib gives no venation and project beyond the apex, ending in a spine. Petioles are thick and quadrangular in shape.
There is tap-root system which produces branches and some of the lateral roots become apo-geotropic, grow vertically upward on the surface of the ground, where they branch repeatedly and form dicotomously branched coral like masses, coralloid roots or corallorhiza that are inhabited by a blue green algae, Anabaena cycadacearum. This cyanophycean algae help the plant to fix atmospheric nitrogen and increase the health and fertility of the soil. The surface of the coralloid roots is beset with lenticel like apertures suggesting their respiratory function.
Sago palm is extensively propagated by vegetative methods by means of adventitious buds or bulbils, which are being formed in the basal part of the stem as well as in the main trunk in mature plants. The plant is asexual (sporophyte) and dioecious in nature ie., the male and female structures namely the cones develop on separate plants. The male cones are borne singly and terminally on the main stem. Further apical growth of the stem is continued by the development of an axillary bud at the base of the cone and it becomes the new stem apex and therefore the stem of the male plant is sympodium. Male cone consists of a central woody axis bearing microsporophylls in a close and compact spiral and each microsporophyll bears a large number of microsporangia bearing microspores. There is no true, compact and properly organised female cone. The male gametophyte phase of the life cycle begins in the microsporangium and the pollen grain is considered to be an immature male gametophyte. The male gamete (sperm) develop inside the pollen grains. The large, top-shaped sperm ranges in size between 180 to 210 � and it is even visible to the naked eye. The megasporophylls arise spirally in acropetal succession and are loosely arranged on the stem like the ordinary crown of foliage leaves. The apical growing point of the female plant thus grows without any interruption and the stem in female plant is monopodial. The megasporophylls are large ranging from six to eight inches in length. Each megasporophyll is divided into an upper broad leafy portion and a lower stalk like portion and the ovules are borne laterally on the lower stalk like portion and its number varies from two to ten. The female gametophyte develops inside the ovule. The plant is generally believed to be wind pollinated. After fertilization, the seeds develop over the summer and are ready to be removed in January or February. Mature seed is differentiated into outer orange red coloured fleshy layer, stony middle layer and fleshy inner layer. Within these seed coats, there is fleshy female prothalus, the endosperm, which functions as the food storage region of the seed. Seed will usually germinate in 3-6 months, but may require more than three years of growth to reach a small bulb like structure.
Sago palm is obviously known to be poisonous and the sago separation includes careful processes to remove these toxins, before they are edible. Intake of sago before proper processing for the removal of toxins can cause vomition, liver damage and even death. Recent evidences indicate that they have neurotoxic effects and now it is considered to be a slow poison. It is remarkable that many indigenous people in different parts of the world have quite independently adopted different processing techniques. Fleshy seeds, leaves, unprocessed flour from stem pith and pollen grains etc are considered to be toxic to the live stock and to the population who live in proximity to these plants, and at the same time it has created interest in the pharmaceutical industry. The general symptoms of the cycas toxicity includes diarrhea, headache, dizziness, vomition and mortality. The major toxic principle in sago palm poisoning is a glycoside named cycasin and other toxic glycosides include macrozamin, neocycasin and an amino acid B-methylamino-L-alanine (BMAA). The active component of the glycosides is methylazoxyglycoside (MAM), which is formed by the cleavage of cycasin (glycosides)
with the help of an enzyme, found in microbes in the gut. Methylazoxyglycoside is known to be hepatotoxic and carcinogenic. It causes apoptosis (programmed cell death) in brain thus reflecting a link between cycad ingestion and development of neurodegenerative disorders. BMAA is a non protein amino acid and it's chemical structure shows similarities to beta-N-oxalylamino-L-alanine (BOAA), the neurotoxin from Lathyrus sativus. There are reports of incidence of Amyotrophic lateral sclerosis (ALS) and Parkinsonism-dementia (PD) after Cycas ingestion. Cycasin and its aglycone MAM impair both rodent and human beta-cell function which may lead to the death of pancreatic islet cells, leads to very high prevalence of glucose intolerance and diabetes mellitus.
1. Stem: Stem starch has been widely used as a food source. Pith and cortical cells contain a large amount of starch and yield �sago� grains and hence the plant is known as the Sago palm. It has been estimated that a mature stem (ie., beginning to flower) about one meter yields about 2 kg of sago, Cycas starch is a constituent of poor man�s food and is used in times of food scarcity. For separating the sago, the trunk of the plants is split and pith like centre is chopped and ground into powder and the starch is removed. Before sago separation there is repeated washing, settling and discarding of the water for the elimination of toxins in it. Ingestion of sago before proper washing leads to vomiting and dizziness. In Japan, the seeds and stems are often used in the preparation of wine. In Africa, for preparing bread from cycads, the central pith of the stem is taken in animal skin and buried in ground for about 40-42 days until it is partially fermented. This fermented stem is ground up with water and is shaped into breads and baked. Crushed bark and seeds or its megasporophylls when mixed with coconut oil are used in S. India as poultice for sores and wounds. Since it contains a toxic glycoside, its constant use is said to cause intestinal disorders and is considered to be genotoxic. Fibre obtained from the stems are used for making cloth, ropes etc.
2. Leaves: The strong and leathery leaves keeps its fresh green colour long after being cut off from the plant and hence it is used as a nursery stock for funeral wreaths and church festivals under the name, palm branches. It is also used to decorate marriage, festival etc. Leaves are used for making brooms, baskets, thatching huts etc. Leaf is also a source of fibre in the manufacture of cloth, ropes, twines etc. Young fleshy leaves are used as vegetables. Consumption of leaves without proper detoxification is harmful and prolonged ingestion of leaves is toxic.
3. Roots: it is a source of sago and in Africa it is believed that burying the roots by a house could protect from lightning.
4. Seeds: Mature palm produce seeds in the female cones. A large plant may yield over 1,000 seeds. Mature seeds are large, orange red in colour. It attracts the animals, birds, rodents, fruit eating bats etc., which help its dispersal. Intake of these seeds by domestic animals is toxic, lead to vomition, dizziness, salivation, paralysis and even mortality, but for wild animals, it is found to be non-toxic. For the separation of the sago, mature seeds are split open and collect the kernel and it is sun dried for one or two days. After thorough drying, the toxins from it are eliminated by keeping it in water for three to six hours and stirred well and drain off the foamy water. This washing process is repeated at least seven times for the total removal of toxins. Thereafter it is dried in sunlight and ground for the preparation of flour. The sago flour is pure white in colour and is similar to that of wheat or rice flour. Natives prepare bread, steam cakes, several indigenous dishes/sweets and even wines. Preparations from the sago palm flour is considered as an effective medicine to cure piles. It is also observed that pregnant women demand sago palm seed flour preparations as part of their pregnancy cravings in pursuit of their attempt to obtain the foods of their choice particularly if they were in the habit of consuming it during their childhood days. Young seeds on boiling yields a decoction, which is often used as purgative.
5. Pollen grains. Pollen grains formed inside the microsporophylls are considered to have medicinal properties. In India quacks claims it as a folk medicine having several health benefits, which obtained from �Kailasam� (The place of Lord Shiva). It has been reported that pollen is heavily laden with cycasin and B-methylamino-L-alanine (BMAA) and is toxic.
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