Hepatotoxic and nephrotoxic principles in Terminalia oblongata

Promising remedies for cardiovascular disease: Natural polyphenol ellagic acid and its metabolite urolithins

BACKGROUND

Cardiovascular disease (CVD) is a significant worldwide factor contributing to human fatality and morbidity. With the increase of incidence rates, it is of concern that there is a lack of current therapeutic alternatives because of multiple side effects. Ellagic acid (EA), the natural polyphenol (C₁₄H₆O₈), is abundant in pomegranates, berries, and nuts. EA and its intestinal microflora metabolite, urolithins, have recently attracted much attention as a potential novel "medicine" because of their wide pharmacological properties.

PURPOSE

This study aimed to critically analyze available literature to summarize the beneficial effects of EA and urolithins, and highlights their druggability and therapeutic potential in various CVDs.

METHODS

We systematically studied research and review articles between 1984 and 2022 available on various databases to obtain the data on EA and urolithins with no language restriction. Their cardiovascular protective activities, underlying mechanism, and druggability were highlighted and discussed comprehensively.

RESULTS

We found that EA and urolithins may exert preventive and curative effects on CVD with negligible side effects and possibly regulate lipid metabolism imbalance, pro-inflammatory factor production, vascular smooth muscle cell proliferation, cardiomyocyte apoptosis, endothelial cell dysfunction, and Ca²⁺ intake and release. Potentially, this may lead to the prevention and amelioration of atherosclerosis, hypertension, myocardial infarction, cardiac fibrosis, cardiomyopathy, cardiac arrhythmias, and cardiotoxicities in vivo. Several molecules and signaling pathways are associated with their therapeutic actions, including phosphatidylinositol 3-kinase/protein kinase B, mitogen-activated protein kinase, NF-κB, nuclear factor erythroid-2 related factor 2, sirtuin1, miRNA, and extracellular signal-regulated kinase 1/2.

CONCLUSION

In vitro and in vivo studies shows that EA and urolithins could be used as valid candidates for early prevention and effective therapeutic strategies for various CVDs.

Characterizations of Six Pomegranate (Punica granatum L.) Varieties of Global Commercial Interest in Morocco: Pomological, Organoleptic, Chemical and Biochemical Studies

Pomegranate variety properties are important not only to demonstrate their diversity but also to satisfy the current market need for high-quality fruits. This study aims to characterize pomological and physico-chemical features as well as the antioxidant capacity of Moroccan local cultivars (Djeibi, Mersi, Sefri 1 and Sefri 2) compared to the imported ones (Mollar de Elche and Hicaz). The pomological characteristics of varieties were relatively diverse. The juice varieties (PJ) displayed a marketed variability in organoleptic and quality properties, such as the flavor, juice yield, and micro/macronutrients contents. Interrelationships among the analyzed properties and PJ varieties were investigated by principal component analysis (PCA). Dimension of the data set was reduced to two components by PCA accounting for 64.53% of the variability observed. The rinds varieties (PR) were studied for their total phenolics, flavonoids, and condensed tannins quantifications. PR varieties extracts exhibited different levels of free radical scavenging activity and local varieties revealed a greater potential with stability over time. The HPLC-DAD analyses of PR extracts revealed (+) catechin as the major compound, where the highest content was found for the local varieties. The SEC analysis showed the molecular weight distribution of phenolic compounds with a high size of condensed tannins formed by the polymerization of the catechin monomer. Given these properties, this research provides an easy selection of high-quality fruits as potential candidates for local market needs.

Effects of Supplementation with a Quebracho Tannin Product as an Alternative to Antibiotics on Growth Performance, Diarrhea, and Overall Health in Early-Weaned Piglets

Simple Summary

The restriction of the use of antibiotics in swine production worldwide has influenced pork production efficiency. New in-feed additives must be sustainable, prevent diarrhea in early weaning piglets, and promote growth performance. Novel in-feed additives, probiotics, prebiotics, organic compounds, mineral salts and vegetable extract have been extensively studied; most have shown some limitations that discourage extensive use. We investigated the plant extract MGM-P (a quebracho tannin product) as an alternative animal feed additive to antibiotics. We considered its unique structure, antibacterial, antioxidant, radical scavenging, and anti-inflammatory activities, and sustainability. We began with a low-level addition trial; 0.3% MGM-P had a more robust effect than 0.2% MGM-P. The findings demonstrated that 0.3% MGM-P supplementation prevented diarrhea in 21-day-old weaned piglets, improving piglet health without adversely influencing growth performance. Practical studies of the mechanisms underlying the effects of MGM-P and the optimal amount for supplementation are needed to confirm our findings.

Abstract

This study assessed the feasibility of using a vegetable extract, MGM-P (quebracho tannin product), as an alternative to antibiotics for weaned piglets; it investigated MGM-P effects on growth performance, diarrhea, and overall health in early-weaned piglets. In total, 24 piglets were allocated to three treatment groups fed basal diets supplemented with 0, 0.2%, or 0.3% MGM-P for 20 days. The addition of 0.3% MGM-P to the diet of early-weaned piglets improved diarrhea incidence, hematological parameters, and intestinal mucosa structure. Furthermore, the addition of 0.2% or 0.3% MGM-P to the diet of early-weaned piglets did not affect their overall health. Importantly, MGM-P had no effects on average daily gain (ADG), average daily feed intake (ADFI), or feed conversion ratio (FCR). Gut morphology analysis showed that treatment with 0.3% MGM-P enhanced the jejunal villus height (p < 0.05) while reducing the ileal crypt depth (p < 0.05) and colon mucosal thickness (p < 0.05). Collectively, the findings suggested that the use of MGM-P as an alternative to dietary antibiotics could improve diarrhea incidence in early-weaned piglets without negative effects on growth performance or overall health.

Impact of polyphenol-rich extracts of Terminalia ferdinandiana fruits and seeds on viability of human intestinal and liver cells in vitro

Terminalia ferdinandiana (Kakadu plum) is a native Australian fruit consumed by Indigenous Australians for centuries. Commercial interest in T. ferdinandiana has increased in recent years due to its high vitamin C content, however, food safety assessments are lacking. To explore the safety of extracts prepared from T. ferdinandiana using different solvents, in vitro cell viability of undifferentiated and differentiated Caco-2, HT29-MTX-E12, and HepG2 cells was measured using the CyQUANT® NF Cell Proliferation Assay. Changes to cell viability produced IC₅₀ values between 3650 and 14400 µg/mL for all extracts and cell lines tested with HepG2 cells impacted the most by T. ferdinandiana extracts, followed by HT29-MTX-E12 cells, and undifferentiated and differentiated Caco-2 cells. Different solvents also produced extracts with variable effects on cell viability that were dependent on tissue source, however, extracts from seedcoats appeared to impact cell viability less than fruit extracts. The IC₅₀ values for ellagic acid, an abundant phytochemical in T. ferdinandiana, varied from 1190 to 2390 µg/mL across different cells and were significantly lower than extract IC₅₀ values. Findings from this study will help to inform future safety studies, select which solvents to use when preparing T. ferdinandiana extracts, and decide whether fruit flesh should be separated from seeds during extract preparation.

Plant and Fungal Hepatotoxicities of Cattle in Australia, with a Focus on Minimally Understood Toxins

Plant- and fungus-derived hepatotoxins are a major cause of disease and production losses in ruminants in Australia and around the world. Many are well studied and described in the literature; however, this is not the case for a number of hepatotoxicities with economic and animal welfare impacts, such as acute bovine liver disease (ABLD), brassica-associated liver disease (BALD) and Trema tomentosa, Argentipallium blandowskianum and Lythrum hyssopifolia toxicity. Additionally, significant overlap in the clinical presentation and pathology of these conditions can present a diagnostic challenge for veterinarians. This review summarizes the current and most recently published knowledge of common plant- and fungus-associated hepatotoxins affecting cattle in Australia, with a focus on the mechanisms of toxicity and distinguishing diagnostic features. Consolidation of the current understanding of hepatotoxic mechanisms in cattle provides insight into the potential mechanisms of lesser-known toxins, including cellular and subcellular targets and potential metabolic pathways. In the absence of specific etiological investigations, the study of epidemiological, clinical and pathological features of hepatotoxicity provides valuable insights into potential toxic mechanisms and is integral for the successful diagnosis and management of these conditions.

Optimization of chromium and tannic acid bioremediation by Aspergillus niveus using Plackett-Burman design and response surface methodology

A chromium and tannic acid resistance fungal strain was isolated from tannery effluent, and identified as Aspergillus niveus MCC 1318 based on its rDNA gene sequence. The MIC (minimum inhibitory concentration) of the isolate against chromium and tannic acid was found to be 200 ppm and 5% respectively. Optimization of physiochemical parameters for biosorption of chromium and tannic acid degradation was carried out by Plackett-Burman design followed by response surface methodology (RSM). The maximum chromium removal and tannic acid degradation was found to be 92 and 68% respectively by A. niveus. Chromium removal and tannic acid degradation was increased up to 11 and 6% respectively after optimization. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) was used to investigate biosorption phenomena.

Ellagitannins in Cancer Chemoprevention and Therapy

It is universally accepted that diets rich in fruit and vegetables lead to reduction in the risk of common forms of cancer and are useful in cancer prevention. Indeed edible vegetables and fruits contain a wide variety of phytochemicals with proven antioxidant, anti-carcinogenic, and chemopreventive activity; moreover, some of these phytochemicals also display direct antiproliferative activity towards tumor cells, with the additional advantage of high tolerability and low toxicity. The most important dietary phytochemicals are isothiocyanates, ellagitannins (ET), polyphenols, indoles, flavonoids, retinoids, tocopherols. Among this very wide panel of compounds, ET represent an important class of phytochemicals which are being increasingly investigated for their chemopreventive and anticancer activities. This article reviews the chemistry, the dietary sources, the pharmacokinetics, the evidence on chemopreventive efficacy and the anticancer activity of ET with regard to the most sensitive tumors, as well as the mechanisms underlying their clinically-valuable properties.

Biological significance of urolithins, the gut microbial ellagic Acid-derived metabolites: the evidence so far

The health benefits attributed to pomegranate have been associated with its high content in polyphenols, particularly ellagitannins. This is also the case for other ellagitannin-containing fruits and nuts including strawberry, raspberry, blackberry, walnuts, and muscadine grapes. The bioavailability of ellagitannins and ellagic acid is however very low. These molecules suffer extensive metabolism by the gut microbiota to produce urolithins that are much better absorbed. Urolithins circulate in plasma as glucuronide and sulfate conjugates at concentrations in the range of 0.2–20 μM. It is therefore conceivable that the health effects of ellagitannin-containing products can be associated with these gut-produced urolithins, and thus the evaluation of the biological effects of these metabolites is essential. Recent research, mostly based on in vitro testing, has shown preliminary evidence of the anti-inflammatory, anticarcinogenic, antiglycative, antioxidant, and antimicrobial effects of urolithins, supporting their potential contribution to the health effects attributed to pomegranate and ellagitannin-rich foods. The number of in vivo studies is still limited, but they show preventive effects of urolithins on gut and systemic inflammation that encourage further research. Both in vivo and mechanistic studies are necessary to clarify the health effects of these metabolites. Attention should be paid when designing these mechanistic studies in order to use the physiologically relevant metabolites (urolithins in gut models and their conjugated derivatives in systemic models) at concentrations that can be reached in vivo.

Metabolism of oak leaf ellagitannins and urolithin production in beef cattle

Oak leaves have a high concentration of ellagitannins. These phytochemicals can be beneficial or poisonous to animals. Beef cattle are often intoxicated by oak leaf consumption, particularly after suffering feed restriction. The severity of the poisoning has recently been associated with the ruminal microbiota, as different bacterial populations were found in animals that tolerated oak leaves and in those that showed clinical and pathological signs of toxicity. Intoxication has previously been linked to the production of phenolic metabolites, particularly catechol, phloroglucinol, and resorcinol. This suggested that the microbial metabolism of ellagitannins could also be associated with its tolerance or intoxication in different animals. Therefore, it is essential to understand the metabolism of ellagitannins in cattle. Here we show that ellagitannins are metabolized in the cattle rumen to urolithins. Different urolithins were detected in ruminal fluid, feces, urine, and plasma. Oak leaf ellagitannins declined as they were converted to urolithins, mainly isourolithin A and urolithin B, by the ruminal and fecal microbiota. Urolithin aglycons were observed in rumen and feces, and glucuronide and sulfate derivatives were detected in plasma and urine. Sulfate derivatives were the main metabolites detected in plasma, while glucuronide derivatives were the main ones in urine. The main urolithins produced in cattle were isourolithin A and urolithin B. This is a relevant difference from the monogastric mammals studied previously in which urolithin A was the main metabolite produced. Low molecular weight phenolics of the benzoic, phenylacetic, and phenylpropionic groups and metabolites such as catechol, resorcinol, and related compounds were also detected. There was a large variability in the kinetics of production of these metabolites in individual animals, although they produced similar metabolites in all cases. This large variability could be associated with the large variability in the rumen and intestine microbiota that has previously been observed. Further studies are needed to demonstrate if the efficiency in the metabolism of ellagitannins by the microbiota could explain the differences observed in susceptibility to intoxication by the different animals.

Preliminary study of the changes in rumen bacterial populations from cattle intoxicated with young oak (Quercus pyrenaica) leaves

Intoxication of grazing cattle occurs repeatedly when they consume large amounts of young oak leaves (OL), which are rich in hydrolysable tannins (HT), due to a shortage of other feed resources. The HT are antimicrobial, although some rumen bacteria can resist or degrade them into potentially toxic or harmless metabolites. To study the effect of the administration of HT-rich OL (Quercus pyrenaica) after a severe feed restriction on the rumen bacterial community and monitor the variations in some bacterial groups that are potentially able to resist or metabolise tannins, three ruminally cannulated bulls were initially fed grass hay and then subjected to a severe 8-day feed restriction period, before receiving OL for 6 days. Then, the animals were again offered grass hay for 12 more days. Rumen contents were sampled throughout the experiment. Quantitative real-time polymerase chain reaction and terminal restriction fragment length polymorphism were used to monitor the bacterial dynamics. Animal 1 was not intoxicated and showed lower relative abundances of Streptococcus bovis initially and after the OL administration than Animals 2 and 3, which showed acute signs of intoxication. The genus Prevotella increased its abundance with the OL administration, whereas Selenomonas ruminantium was reduced. The bacterial terminal restriction fragment length polymorphism profile of Animal 1 clustered initially separately from Animals 2 and 3 and was less affected by the feed restriction period. These results showed that the effect of the consumption of HT-rich OL after a severe feed restriction is highly variable in cattle and might rely on the individual composition of the microbiota colonising the rumen.

Safety evaluation of an oak-flavored milk powder containing ellagitannins upon oral administration in the rat

Ellagitannins are phenolic compounds that occur in a number of dietary sources such as walnuts, raspberries, pomegranate, strawberries, and oak-aged wines. Ellagitannins have been acknowledged to have antioxidant and cancer chemopreventive activities. However, ellagitannins have also been considered to be "antinutrients" and have been reported to provoke adverse effects in animals. In this context, risk assessment studies are demanded to ensure that chemicals present in food do not compromise food safety. Oak-flavored milk can be obtained by thermal treatment of milk in the presence of oak shavings. The oak-flavored milk can be used to impart wood-like flavor to different recipes. The present study evaluated, under a subchronic approach, the safety of an oak-flavored milk powder containing ellagitannins in rats upon repeated oral administration for 96 days. The effect of 30% oak-flavored milk powder in the diet was evaluated. This amount involved a margin of safety equivalent to the daily intake of 134 yogurts by a 70 kg person for 96 days. Growth rate, food utility index, 9 hematological, and 13 serobiochemical parameters as well as the metabolism and tissue distribution of ellagitannins and derived metabolites were studied. Overall, no significant differences were found in oak-milk-fed rats in any blood parameter analyzed. No effect was found on growth rate and food utility index. Urolithin A was identified in feces of rats fed oak-flavored milk and the glucuronide derivative in urine. No metabolites were found in the liver, kidney, or uterus. Histopathological analysis of liver and kidney corroborated the absence of toxicity. Therefore, these results suggest that the intake of the oak-flavored milk powder assayed in this study is safe and does not involve potential hazard to human health.

Octanol-water partition coefficients for predicting the effects of tannins in ruminant nutrition

Tannins can cause beneficial or harmful nutritional effects, but their great diversity has until now prevented a rational distinction between tannin structures and their nutritional responses. An attempt has been made to study this problem by examining the octanol-water solubilities of tannins. A relatively simple HPLC method has been developed for screening mixtures of plant tannins for their octanol-water partition coefficients (Kow coefficients). Tannins were isolated from the fruits and leaves of different Acacia, Calliandra, Dichrostachys, and Piliostigma species, which are known to produce beneficial or harmful effects. The Kow coefficients of these tannins ranged from 0.061 to 13.9, average coefficients of variation were 9.2% and recoveries were 107%. Acacia nilotica fruits and leaves had the highest Kow coefficients, that is, 2.0 and 13.9, respectively. These A. nilotica products also have high concentrations of tannins. The combined effects of high octanol solubilities and high tannin concentrations may explain their negative effects on animal nutrition and health. It is known that compounds with high octanol solubilities are more easily absorbed into tissues, and it is, therefore, proposed that such compounds are more likely to cause toxicity problems especially if consumed in large quantities. According to the literature, tannins in human foods tend to have low Kow coefficients, and this was confirmed for the tannins in Piliostigma thonningii fruits. Therefore, unconventional feeds or browse products should be screened not only for their tannin concentrations but also for low octanol-water partition coefficients in order to identify nutritionally safe feeds and to avoid potentially toxic feeds.

Nephrotoxicity associated with exposure to plant toxins, with particular reference to Africa

Acute renal failure is a frequent cause of morbidity and mortality in the hospitalized population worldwide. In Africa, apart from hemodynamic causes and infections, herbal remedies contribute to both morbidity and mortality, although these causes often go unrecognized. This paper reviews reports of herbal remedies that have been shown to result in nephrotoxicity. The indications for use of the remedies, signs and symptoms in poisoned patients, and the methods used to detect toxic compounds in plant specimens or in biological fluids are covered.

Repeated oral administration of high doses of the pomegranate ellagitannin punicalagin to rats for 37 days is not toxic

The water-soluble ellagitanin punicalagin has been reported to be toxic to cattle. Taking into account that this antioxidant polyphenol is very abundant in pomegranate juice (> or =2 g/L), the present study evaluated the possible toxic effect of punicalagin in Sprague-Dawley rats upon repeated oral administration of a 6% punicalagin-containing diet for 37 days. Punicalagin and related metabolites were identified by HPLC-DAD-MS-MS in plasma, liver, and kidney. Five punicalagin-related metabolites were detected in liver and kidney, that is, two ellagic acid derivatives, gallagic acid, 3,8-dihydroxy-6H-dibenzo[b,d]pyran-6-one glucuronide, and 3,8,10-trihydroxy-6H-dibenzo[b,d]pyran-6-one. Feedstuff intake, food utility index, and growth rate were lower in treated rats during the first 15 days without significant adverse effects, which could be due to the lower nutritional value of the punicalagin-enriched diet together with a decrease in its palatability (lower food intake). No significant differences were found in treated rats in any blood parameter analyzed (including the antioxidant enzymes gluthatione peroxidase and superoxide dismutase) with the exception of urea and triglycerides, which remained at low values throughout the experiment. Although the reason for the decrease is unclear, it could be due to the lower nutritional value of the punicalagin-enriched diet with respect to the standard rat food. Histopathological analysis of liver and kidney corroborated the absence of toxicity. In principle, the results reported here, together with the large safety margin considered, indicate the lack of toxic effect of punicalagin in rats during the 37 day period investigated. However, taking into account the high punicalagin content of pomegranate-derived foodstuffs, safety evaluation should be also carried out in humans with a lower dose and during a longer period of intake.

Influence of the polyphenolic tannic acid on the toxicity of the insecticide deltametihrin to fish. A comparative study examining both biochemical and cytopathological parameters

Humics and pesticides are present in aquatic environment and the toxicological consequences of their chemical interaction is well studied. However, data concerning the mechanism of the biochemical action of humic-pesticide combinations are scarce, especially in vertebrates. Thus we have chosen to study the in vivo effects of the plant polyphenolic tannic acid and the pyrethroid insecticide deltamethrin [Decis] alone or in combination on hepatic xenobiotic-metabolizing enzyme activities and the associated redox-parameters in carp, as the complex assessment of these systems are regarded to serve as a relevant biomarker of environmental pollution. Stress effects and tissue damage were followed by determination of the plasma glucose level, the activities of plasma transaminases, and by electron microscopy. Tannic acid alone exerted weak prooxidant effect due to its marked antioxidant enzyme inhibitory activity. Deltamethrin, applied in a very low dose, induced oxyradical production in fish via activation of cytochrome P450 isozymes. This effect was promoted by the antioxidant enzyme inhibitory action of tannic acid, when the two chemicals were combined; however, the ultrastructural damage of the hepatocytes was reduced by the common cytoprotective capacity of the phenolic. Numerous humics are known to alter the toxicity of pesticides and their influence depends on their type and concentration. Therefore, our work taken together with other comparative studies may contribute to the assessment of the impact of humics in nature, especially in case of environmental pollution.

Spironucleosis in Australian king parrots (Alisterus scapularis)

OBJECTIVE

To describe a syndrome of wasting, diarrhoea and mortality in Australian king parrots (Alisterus scapularis).

DESIGN

Field observations and laboratory examinations. Procedure Pathological examinations were performed on 50 Australian king parrots with wasting and diarrhoea. Wet preparations of intestinal contents were examined by light microscopy. Tannins were extracted from acorns (Quercus sp) and tested for toxicity in mice. CLINICAL SIGNS AND EPIDEMIOLOGY: A syndrome of wasting, diarrhoea and mortality was observed in wild juvenile Australian king parrots in eastern Australia from 1984 to 2000. Sporadic cases and outbreaks of disease occurred from May to September in New South Wales, the Australian Capital Territory and Victoria. Outbreaks in the Australian Capital Territory in 1990 and 1991 were associated with parrots congregating to feed on acorns. Most affected birds failed to respond to treatment with dimetridazole and died 1 to 14 days after hospitalisation. Selected cases recovered following treatment with metronidazole.

PATHOLOGY

Affected birds were emaciated, with faecal matting of feathers around the cloaca and yellow-green fluid, foamy intestinal contents. Abundant motile Spironucleus trophozoites were observed in wet preparations of faeces of clinically affected birds and intestinal contents of birds examined within 1 h of death. Protozoa were detected histologically in crypts of Lieberkühn in the intestine in association with exudation of mucus (catarrhal enteritis) or lymphoplasmacytic enteritis. Toxicology Tannin extracts from acorns induced periacinar hepatic necrosis in mice.

CONCLUSION

Wasting, diarrhoea and mortality in wild juvenile Australian king parrots were associated with Spironucleus-like protozoa in the intestine. Acorns were not considered to be the cause of the syndrome.

Antioxidant activity of pomegranate juice and its relationship with phenolic composition and processing

The antioxidant activity of pomegranate juices was evaluated by four different methods (ABTS, DPPH, DMPD, and FRAP) and compared to those of red wine and a green tea infusion. Commercial pomegranate juices showed an antioxidant activity (18-20 TEAC) three times higher than those of red wine and green tea (6-8 TEAC). The activity was higher in commercial juices extracted from whole pomegranates than in experimental juices obtained from the arils only (12-14 TEAC). HPLC-DAD and HPLC-MS analyses of the juices revealed that commercial juices contained the pomegranate tannin punicalagin (1500-1900 mg/L) while only traces of this compound were detected in the experimental juice obtained from arils in the laboratory. This shows that pomegranate industrial processing extracts some of the hydrolyzable tannins present in the fruit rind. This could account for the higher antioxidant activity of commercial juices compared to the experimental ones. In addition, anthocyanins, ellagic acid derivatives, and hydrolyzable tannins were detected and quantified in the pomegranate juices.

Isolation and structure determination of terminalin A toxic condensed tannin from Terminalia oblongata

Terminalia oblongata (yellow wood) is a small deciduous tree growing over an area of central Queensland that supports a large proportion of this state's cattle population. Cattle and sheep that consume yellow wood leaves are poisoned and die. Severe losses of these animals can occur, and this problem is considered the main cause of economic loss to the cattle industry in the area apart from drought. A new toxic condensed tannin, terminalin was isolated from Terminalia oblongata. Its structure was deduced following NMR, IR, UV, MS analyses and in the knowledge that these data show good correlations to those obtained from the related punicalagin molecule which is present in the plant. Terminalin has a high toxicity (20 mg/kg) to white Quackenbush male mice and produces a vascular renal necrosis with slight liver necrosis, unlike punicalagin, which produces liver lesions but not kidney lesions. Similar results were obtained with sheep. A most interesting aspect is that there are two different specific toxins in the plant.

Experimental acute yellow-wood (Terminalia oblongata) intoxication in sheep

An aqueous suspension of air-dried, hammer-milled leaf of Terminalia oblongata (yellow-wood) was administered to sheep by gavage, as a single dose of 5 to 20 g (dry weight)/kg body weight. Doses of 15 g/kg, or more, caused depression, inappetence, abdominal pain and reduced ruminal movements within 24 to 48 h and some sheep also showed dyspnoea, opisthotonus and champing of the jaws. Haematology and blood gas and acid-base measurements were unaffected. In sheep given a dose of 12.5 g/kg, or more, plasma osmolality, aspartate aminotransferase activity and potassium and bilirubin concentrations increased while plasma total protein markedly decreased and plasma sodium concentration and alkaline phosphatase activity remained normal. Most sheep were necropsied 48 h after dosing. The liver showed zonal hepatocellular necrosis, the pattern of which varied with the dose given. No renal lesions were observed, although one sheep given a very high dose became azotaemic and hyperkalaemic. Hydrothorax, hydropericardium and ascites developed in sheep given doses of 15 or 20 g/kg.

Tannic acid intoxication in sheep and mice

Acute tannic acid intoxication was studied in mice and sheep. In mice, following oral administration of 2.0 to 4.6 g of tannic acid kg-1 bodyweight, periacinar coagulative and haemorrhagic necrosis occurred in the liver. In sheep, following oral (8 g kg-1 bodyweight) administration of tannic acid, liver necrosis was not observed either histologically or detected biochemically, although transmission electron microscopy showed focal hepatocellular necrosis, steatosis and acicular crystal cleft formation. In sheep given tannic acid intraperitoneally (0.1 g kg-1 bodyweight), liver necrosis occurred and plasma sodium and glucose levels significantly (P < 0.05) decreased while packed cell volume and plasma aspartate aminotransferase, alkaline phosphatase, creatinine and bilirubin significantly (P < 0.01) rose. The results for blood-gas and acid-base determinations, blood haemoglobin and oxygenation showed significant increases in arterial blood methaemoglobin concentration (P < 0.05) and decreases in blood pH (P < 0.01) and oxyhaemoglobin concentration (P < 0.05) in sheep by 32 hours after oral dosing with 8 g of tannic acid kg-1 bodyweight. In sheep given tannic acid intraperitoneally, methaemoglobinaemia was not detected, but metabolic acidosis with a compensatory respiratory alkalosis occurred. Thus, it would appear that although tannic acid is hepatotoxic when given orally to mice or intraperitoneally to sheep, it does not produce renal or significant hepatic injury in sheep when given orally, but rather causes metabolic acidosis and methaemoglobinaemia.

Determination of tannic acid and its phenolic metabolites in biological fluids by high-performance liquid chromatography

A method for the identification and determination of tannic acid and its phenolic metabolites in biological fluids by high-performance liquid chromatography was developed. Tannic acid and four phenolic compounds, namely gallic acid, pyrogallol, 4-O-methylgallic acid and ellagic acid, were successfully extracted from the biological fluids by using ethyl acetate at acidic conditions. Gallic acid, pyrogallol and 4-O-methylgallic acid were found in the sheep urine, gallic acid, 4-O-methylgallic acid and ellagic acid in plasma, and gallic acid and ellagic acid in abomasal fluid after abomasal dosing of tannic acid. Tannic acid was found in the plasma apart from the abomasal fluid into which it was administered. The concentrations of tannic acid, gallic acid, pyrogallol, 4-O-methylgallic acid and ellagic acid in plasma, abomasal fluid and urine were measured. This method could be applied to measurement of other hydrolysable tannins and their phenolic metabolites in biological materials.