A critical review on carotenoid research in Sri Lankan context and its outcomes.

As determined by countrywide assessments, vitamin A deficiency is a public health problem in Sri Lanka. Study of carotenoid profile and content could be important to nutritionists as some carotenoids act as precursors of vitamin A. Sri Lanka has a remarkable diversity of carotenoid sources. A number of Sri Lankan sources of carotenoids have been studied by many authors. This study reviews carotenoid research done in Sri Lanka, comparing results which are generally in conflict with a few relevant studies abroad, while focusing on problems of carotenoid research and concluding that it is difficult for a dietician to predict carotenoid intake due to marked biological variation. Therefore, any database on carotenoid covering the entire country has its limitations. Further that even if carotenoid profiles are known using exhaustive sampling, there can be no single method of calculating retinol equivalent (RE) and retinol activity equivalent (RAE) especially as carotenoid uptake and bioconversion could be multifactorially affected and subject to control mechanisms. Therefore, RE and RAE should be calculated differently for different types of plant materials may even be expanded so that a unique calculation depending on plant material and method of cooking.

Bioactivity of cinnamon with special emphasis on diabetes mellitus: a review.

Cinnamon is the oldest spice and has been used by several cultural practices for centuries. In addition to its culinary uses, cinnamon possesses a rising popularity due to many stated health benefits. Out of the large number of cinnamon species available, Cinnamomum aromaticum (Cassia) and Cinnamomum zeylanicum have been subjected to extensive research. Available in vitro and in vivo evidence indicates that cinnamon may have multiple health benefits, mainly in relation to hypoglycaemic activity. Furthermore, the therapeutic potential of cinnamon is stated also to be brought about by its anti-microbial, anti-fungal, antiviral, antioxidant, anti-tumour, blood pressure-lowering, cholesterol and lipid-lowering and gastro-protective properties. This article provides a summary of the scientific literature available on both C. aromaticum and C. zeylanicum. All studies reported here have used cinnamon bark and its products. Although almost all the animal models have indicated a pronounced anti-diabetic activity of both cinnamon species, conflicting results were observed with regard to the few clinical trials available. Therefore, the necessity of evaluating the effects of cinnamon for its therapeutic potential through well-defined and adequately powered randomized controlled clinical trials is emphasized, before recommendations are made for the use of cinnamon as an effective treatment for humans.

A review of the neurotoxic effect of palmyrah flour.

The present review covers the history of the neurotoxic effect of palmyrah (Borassus flabellifer L). The chemical nature of the active synergists is isomers of a spirostane tetraglycoside containing three rhamnosyl residues and one glucosamine where the position of the NH(2) appears to be the difference in the saponins. As neurotoxicity has not been reported in humans consuming palmyrah flour, it is hypothesized that this may be due to one or more of the following: a species effect; the mode of processing flour and cooking palmyrah flour recipes containing these water-soluble and dry-heat decomposable saponin primary amines; frequency of consumption of palmyrah flour-based products; and the nutritive value of other dietary components. It is hypothesized that the Hepatotoxic syndrome as reported previously is due to a collective effect of a number of biologically active compounds, most of which are water-soluble saponins, like neurotoxins.

A study of the serum carotenoids of eight cases of hypercarotenemia in Sri Lanka.

Over-consumption of absorbable carotenoids causes hypercarotenemia. Although hypercarotenemia is detected in Sri Lanka, a detailed study on this condition has not been carried out previously. Two millilitres of venous blood was drawn from hypercarotenemic patients (n=8) and examined by high-performance liquid chromatography for carotenoids and vitamin A. A common high-performance liquid chromatographic pattern in serum was shown by six of the cases with beta-carotene (9.9-35.7 microg/dl), beta-cryptoxanthin and monohydroxy metabolites collectively (5.3-48.5 microg/dl), and six to eight metabolites of dihydroxy, trihydroxy and polyhydroxy metabolites (22.5-282.1 microg/dl). Vitamin A levels were within the normal range (32-61 microg/dl). However, two cases identified were abnormal. The first of these showed low beta-carotene (3.5 microg/dl) and no beta-cryptoxanthin and monohydroxy metabolites, but normal dihydroxy, trihydroxy and polyhydroxy metabolites (128.2 microg/dl). However, the vitamin A level was high (75.2 microg/dl). The other case showed high beta-carotene (212.3 microg/dl) and beta-cryptoxanthin (49.3 microg/dl) but no normal monohydroxy, dihydroxy, trihydroxy and polyhydroxy metabolites. Instead there was an atypical metabolite (343.9 microg/dl). According to the present study, excessive intake of boiled, homogenized carrot and ripe papaw is the main causative factor for hypercarotenemia. Over-consumption of carotenoids-rich plant foods may be complicated in the case of individuals having defects of either the control of the 15,15'-dioxygenase activity or metabolism of carotenoids.

The neurotoxic effect of palmyrah (Borassus flabellifer) flour re-visited.

The neurotoxic effect of palmyrah (Borassus flabellifer L.) shoot flour on Wistar rats has been reported previously by Arseculeratne and co-workers. A deficiency in previous studies was an inadequate description of the methodology, especially on the composition and consumption of test and control feed, and weight gain/losses. This study shows that feeds containing 100% and 70% palmyrah flour result in very little or no feed consumption, and deaths reported could have been interpreted as being due to starvation. A mixture of 50% palmyrah flour and 50% standard breeding feed results in the neurotoxic symptoms such as muscle in-coordination, spasms and immobility of hind limbs reported previously (Arseculeratne and coworkers). These neurotoxic symptoms can be eliminated by heating the palmyrah flour at 80 degrees C for 45 min; that is, detoxification. Attempts were made to reproduce the neurotoxic effect by administering two-fold palmyrah flour extractive compared with that contained in the same flour consumed by experimental rats per day. This did not produce a neurotoxic effects (as reported previously while using rats fed on standard breeding feed). It is interpreted that the nutritional status of the diet influences that manifestation of the neurotoxic effect; the effect being suppressed with a nutritious diet. Studies on the blood enzyme levels of rats showed that while alanine aminotransferase was not affected, aspartate aminotransferase was significantly affected by oral administration of organic solvent-free water and methanol:water (1:1) extractives (P = 0.023 and P = 0.0044), respectively. This study shows that while the reported hepatotoxin is not extracted by these solvent systems, there appears to be a tissue non-specific cellular damage reflected at a subclinical level.

Oral hypoglycaemic activity of Ipomoea aquatica in streptozotocin-induced, diabetic wistar rats and Type II diabetics.

Ipomoea aquatica Forsk is a common green leafy vegetable consumed in many parts of the world. The present study was designed to investigate the oral hypoglycaemic activity of Ipomea aquatica in streptozotocin induced diabetic Wistar rats, and Type II diabetic patients. Experimental diabetes was induced with streptozotocin in Wistar rats. The rats were then divided into test and control groups. In addition to the standard feed given to both groups the test was fed with the shredded leaves of Ipomoea aquatica (3.4 g/kg) for one week. Type II diabetic patients were subjected to a glucose challenge before and after a single dose of blended I. aquatica. Patients acted as their own controls. The results revealed that consumption of the shredded, fresh, edible portion of I. aquatica for one week, effectively reduced the fasting blood sugar level of streptozotocin-induced diabetic rats (p = 0.01). When subjected to a glucose challenge, the Type II diabetic subjects showed a significant reduction (p = 0.001) in the serum glucose concentration 2 h after the glucose load. However, it was not significantly reduced at 1 h (p < 0.09) post glucose load. There was a 29.4% decrease in the serum glucose concentration of the diabetic patients when treated with the plant extract.

Effect of exogenous histidine and Garcinia cambogia on histamine formation in skipjack (Katsuwonus pelamis) homogenates.

Histamine consumed with food gives rise to allergic reactions. Dark muscle fish, for example skipjack (Katsuwonus pelamis) has been shown to contain histamine. Studies using TLC (acetone: NH4OH, 80:20.5) on silica gel G60 plates and densitometry after spraying with ninhydrin, using a computerized densitometer, showed that freshly harvested skipjack has no detectable histamine (detection limit, 50 micrograms.g-1 fish). However, with time histamine (Rf 0.84) is formed > 1.5 mg.g-1 probably through microbial action. Skipjack contains high levels of free histidine at levels of > 10 mg.g-1 (Rf 0.41) but fish like seer (Scomberamous spp.), which are not reported to be allergenic, contain < 4 mg.g-1 histidine. Addition of exogenous histidine (50 mg.g-1) results in histamine formation in seer 2.2-fold that of skipjack under the same conditions. A type of herring (Amblygaster spp., sinhala-hurulla) is not a histamine former, but had been shown to cause allergenic reactions, resulting in a ninhydrin positive spot (Rf 0.79) on incubating for 24 hours. Addition of arginine and lysine to blended skipjack results in their loss probably by decarboxylation. Addition of the spice Garcinia cambogia (extracts 0.2 g ml-1) known as 'goraka' in Sri Lanka (sinhala) and 'kukum' in India (hindhi), to fresh skipjack incubates prevents histamine formation as a results of lowering pH to 3.2-3.6 whereas Avverhoea bilimbi (bilin) and Tamarindus indica (tamarind) extracts did not prevent histamine formation.

An aqueous extract of the green leafy vegetable Ipomoea aquatica is as effective as the oral hypoglycaemic drug tolbutamide in reducing the blood sugar levels of Wistar rats.

This study was undertaken to compare the oral hypoglycaemic activity of an aqueous extract of the green leafy vegetable Ipomoea aquatica (dose equivalent to 3.3 g starting material /kg body weight) with that of the known oral hypoglycaemic drug tolbutamide (15 mg/kg body weight) in glucose challenged Wistar rats (3 g/kg body weight, administered 30 min after the administration of Ipomoea aquatica or tolbutamide). One and half hours after administration of glucose (equivalent to 2 h after administration of plant extract or tolbutamide), the mean blood glucose level of the Ipomoea aquatica treated group was 47.5% lower than that of the control group treated with distilled water. The tolbutamide treated group showed a mean blood glucose level which was only 33.8% lower than that of the control group. However, statistical analysis indicated that the blood glucose levels of the Ipomoea aquatica treated group were not significantly different from that of the tolbutamide treated group. Our results show that the aqueous extract of Ipomoea aquatica is as effectve as tolbutamide in reducing the blood glucose levels of glucose-challenged Wistar rats.

Glycaemic indices of different varieties of rice grown in Sri Lanka.

OBJECTIVE: Varieties of red raw rice are widely believed to have a better nutritional quality. The physiological effects of consuming different varieties of rice may not be so. The glycaemic index has been developed as an indicator of the physiological effect of foods. It is the glycaemic response of a 50 g carbohydrate portion of food expressed as a percentage of that of a standard. The objective of this study was to determine the glycaemic indices of different varieties of rice grown in Sri Lanka. DESIGN: Digestible carbohydrate content of 11 varieties of rice flour and bread were determined. Fasting blood samples followed by half-hourly samples for two hours were drawn after giving portions of either cooked rice or bread containing 50 g carbohydrate each. SETTING: Fibre mill in Gampaha district. SUBJECTS: Twenty-two fibre mill workers aged between 25 and 50 years. MEASUREMENTS: The area under the blood glucose curve (AUC) for varieties of rice for a subject was calculated. Average AUC of 3 values for bread were calculated. Glycaemic index of each variety of rice was determined from the above variables. RESULTS: Glycaemic indices of varieties of rice differ. The glycaemic indices of varieties of red raw rice varied between 56 and 73 and the variety Bg 350 had the lowest glycaemic index. There was no significant difference between mean glycaemic index of varieties of white raw and some varieties of red raw rice (p = 0.2). Parboiled varieties of red raw rice had a significantly lower glycaemic index than white raw rice (p = 0.04) and some of the red raw rice (p = 0.005). CONCLUSIONS: The glycaemic index cannot be predicted from the colour of the rice grain. Red parboiled varieties of rice and Bg 350 can be recommended for patients with diabetes.

Literature review of an underutilized legume: Canavalia gladiata L.

The literature related to the legume commonly known as sword beans (Canavalia gladiata) that belongs to the genus Canavalia which is considered to be an underutilized legume, is reviewed. The legume seeds are considered to be a cheap source of good protein and calories that are easily available. However, even with this knowledge, the utilization of most legumes is apparently low. Sword beans have favorable agronomic features suitable for cultivation in the tropics and a high average yield comparable to that of soybeans. The agroclimatic conditions suitable for cultivation, morphological features, uses, chemical composition and the antinutritional factors of the plant are discussed.

Nutritional evaluation of protein and starch of mature Canavalia gladiata seeds.

Evaluation of true digestibility (TD), biological value (BV) and net protein utilisation (NPU) of diets made with raw and processed seed flour from mature Canavalia gladiata seeds were carried out with male Sprague-Dawley rats. The weight gain of the rats fed with diets containing raw whole seed and raw cotyledon alone were significantly lower (P = 0.05) than that of the group fed with the reference diet. Processing the cotyledons (dry-autoclaved or roasted) significantly (P < or = 0.05) increased the weight gain of the rats when compared to the weight gain of rats fed diets prepared with raw seed flour. NPU of raw (whole seed 13.8; cotyledon 27.6) was significantly lower (P < or = 0.05) than the reference diet (79.5). The NPU of processed samples was also significantly lower (P < or = 0.05) when (dry-autoclaved 25.1; roasted 25.1) compared to the reference diet fed group (79.5). The BV of the processed samples (dry-autoclaved 31.1; roasted 37.7) was significantly lower (P < or = 0.05) than that of raw (53.6) cotyledon. In contrast TD increased (P < or = 0.05) with processing (dry-autoclaved 80.9; roasted 65.9) when compared to raw cotyledon (51.4). In vitro protein digestibility for the raw whole seed and cotyledon was 71.7 and 70.1% respectively. In vitro starch digestibility of raw and processed cotyledon flour samples indicated dry-autoclaved sample to have the highest digestibility.

Oral hypoglycaemic activity of Ipomoea aquatica.

Ipomoea aquatica is a commonly consumed green leafy vegetable in Sri Lanka which is supposed to possess an insulin-like activity [Jayaweera, D.M.A., 1982. Medicinal Plants (Indigenous and Exotic) Used in Ceylon. Part 11. National Science Council, Colombo, Sri Lanka, pp. 99]. Only a little attention has been paid to the therapeutic use of this plant. We studied the oral hypoglycaemic activity of single and multiple doses of I. aquatica in healthy, male Wistar rats after a glucose challenge. There was a significant reduction in the serum glucose concentrations with both single (33%, P<0.0027) and multiple (25%, P<0.02) doses. The optimum dose was 3.4 g/kg while the optimum activity was given 2 h after the administration of the extract. The present study indicates that a boiled, whole extract of I. aquatica exerts an oral hypoglycaemic effect in healthy, male, Wistar rats after a glucose challenge.