Contribution of a high dose of L-ascorbic acid to carnitine synthesis in guinea pigs fed high-fat diets.

Ascorbate is a cofactor of two-enzyme hydroxylation in the pathway of carnitine biosynthesis. The purpose of this study was to investigate the contribution of ascorbate to endogenous carnitine in guinea pigs fed high-fat diets. The contents of carnitine in plasma, urine and tissues of guinea pigs supplemented with L-ascorbic acid were determined and compared with those supplemented with carnitine. Albino-Hartley guinea pigs were fed vitamin C-deficient diets containing lard throughout the experiment. They were administered orally with 5 mg L-ascorbic acid/d/animal for 14 d, and then divided into three groups and administered orally with the following supplements (/d/animal) for 14 d; L (5 mg L-ascorbic acid), LASA (100 mg L-ascorbic acid), and LCAR (10 mg carnitine plus 5 mg L-ascorbic acid). As a control, a normal group was fed vitamin C-deficient diets and administered orally with 5 mg L-ascorbic acid/d/animal for 28 d. The animals fed high-fat diets (L group) had higher free-carnitine contents in the muscle and urine than the normal group. The groups of LCAR and LASA had significantly higher contents of acid-soluble carnitine (p < 0.05) in plasma than the L group. Urinary excretion of carnitine in the LASA group was decreased to the same level as that in the normal group, although no significant difference between the groups of L and LCAR was observed. Moreover, the supplement of ascorbic acid, but not of carnitine, induced a significantly lower content of triacylglycerol in the plasma of the LASA group as compared to the L group (p < 0.05). These data suggest that high doses of ascorbic acid in guinea pigs fed high-fat diets contribute to the enhancement of carnitine synthesis and improvement of the triacylglycerol content in the plasma.     

Elevated levels of dietary ascorbic acid increase immune responses in channel catfish

Channel catfish fingerlings were fed purified diets containing 0 to 3000 mg/kg of ascorbic acid until external signs of scurvy were seen in the fish fed the ascorbic acid-deficient diet. At this time, resistance to bacterial infection, antibody production, complement activity and phagocytic activity were assessed for fish from the various dietary treatments. Mortality rates of fish experimentally infected with Edwardsiella ictaluri, the bacterium causing enteric septicemia in channel catfish, decreased with increases in dietary ascorbic acid doses, ranging from 100% for fish fed the ascorbic acid-deficient diet to 15% for fish fed 300 mg ascorbic acid per kilogram diet and 0 for fish fed 3000 mg ascorbic acid per kilogram diet. Antibody response to E. ictaluri antigen, hemolysis of sensitized sheep erythrocytes by complement activity and phagocytic engulfment of E. ictaluri by peripheral phagocytes were each impaired in fish fed the diet without supplemental ascorbic acid; intracellular bactericidal activity of the phagocytes was not affected by ascorbic acid deficiency. There were no differences in antibody production, complement activity, or phagocytic activities among fish fed diets containing 30-300 mg ascorbic acid/kg of diet. However, the dose level of 3000 mg ascorbic acid/kg significantly enhanced antibody production and complement activity.     

Synergistic effect of vitamin C and aspirin on gastric lesions in the rat.

The effects of varying levels of dietary vitamin C on the incidence of aspirin-induced gastric hemorrhagic lesions were studied in young, male rats. Rats fed diets containing either 20, 40, or 60 mg of L-ascorbic acid per gram of diet did not exhibit focal gastric lesions. Administering a single oral dose of aspirin (30 mg aspirin/100 g of body weight) to rats fed control diets produced gastric lesions. When the rats were given aspirin plus a diet containing either 40 or 60 mg ascorbic acid per gram of diet, there was a significant increase in number of gastric lesions. Since vitamin C and aspirin seem to act synergistically in producing hemorrhagic lesions in the stomach, it is recommended that all individuals taking megadoses of vitamin C be cautioned against taking aspirin concurrently.     

The tissue distribution of L-ascorbic acid and dehydro-L-ascorbic acid in the guinea pigs injected intravenously with dehydro-L-ascorbic acid

The tissue distribution of L-ascorbic acid (AsA) and dehydro-L-ascorbic acid (DAsA) in guinea pigs injected with DAsA intravenously was examined using high-performance liquid chromatography. DAsA injected into guinea pigs fed normal diets containing AsA (control group) was readily taken into erythrocytes, and AsA contents of plasma and other tissues rapidly increased after DAsA injection. In animals fed vitamin C-deficient diets, DAsA was also detected in erythrocytes; however, the increase of AsA in their tissues was considerably less than that of control group. From these results, it was suggested that utilization of DAsA as AsA in vitamin C-deficient guinea pigs was less than that of control animals, and the reduction mechanism of DAsA to AsA in vitamin C-deficient guinea pigs may have differed from that of control groups.     

Effect of dietary ascorbic acid and vitamin E on metabolic changes in rats and guinea pigs exposed to PCB

The effect of the addition of dietary ascorbic acid and/or vitamin E (all-rac-alpha-tocopheryl acetate) in rats and guinea pigs exposed to PCB (polychlorinated biphenyls) was studied. Rats were fed diets containing one of three levels of vitamin E (30, 500 or 1000 mg/kg diet) with or without PCB (200 mg/kg diet). Guinea pigs were fed diets containing PCB (40 mg/kg diet) with 200 or 1000 mg ascorbic acid/kg diet and/or 70 or 2000 mg vitamin E/kg diet. For rats fed PCB, ascorbic acid in urine was 40-fold higher and in liver, 2-fold higher than for rats fed no PCB, and thiobarbituric acid-reactive substances (TBA-RS, indicators of lipid peroxidation) in liver was 1.5-fold higher. In rats fed PCB, high dietary vitamin E significantly lowered the urinary ascorbic acid and TBA-RS. Liver ascorbic acid was lowered by high dietary vitamin E only in control rats. In guinea pigs, feeding PCB caused severe growth retardation and the liver TBA-RS was 1.8-fold higher than in guinea pigs not fed PCB. Feeding high levels of both ascorbic acid and vitamin E was more effective in reversing the growth depression and in lowering TBA-RS level (due to PCB) than feeding the vitamins separately. Ascorbic acid metabolism in rats was affected by high dietary vitamin E. The possibility of a higher requirement for ascorbic acid and vitamin E in guinea pigs exposed to PCB was indicated. Interaction of ascorbic acid and vitamin E in animals exposed to PCB was suggested.     

Alternative complement activity and resistance to heat stress in golden shiners (Notemigonus crysoleucas) are increased by dietary vitamin C levels in excess of requirements for prevention of deficiency signs

Golden shiners (Notemigonus crysoleucas) require a dietary source of ascorbic acid (AA) for growth or survival, depending on diet composition. However, no quantitative requirements of golden shiners for AA for growth, health or survival have been determined, and specific deficiency signs have not been observed. The purpose of this study was to determine the effects of different dietary levels of AA on the growth and health of golden shiners fed diets containing 0-218.5 mg AA/kg diet for 10-16 wk. Weight gain, survival and gross deformities were assessed at 10 wk. The remaining fish were fed the same diets from wk 11-16; hematology and alternative complement activity were then assessed and a subset of live fish from each tank was exposed to elevated temperature. Gross deformities appeared in fish fed 0 mg AA/kg diet at 9 wk. The 19.5 mg AA/kg diet was sufficient to prevent the deformities and optimize survival, whereas growth did not differ among treatments. Fish fed 40.3 mg of AA/kg diet had a higher survival rate than fish fed 0 or 19.5 mg AA/kg diet after exposure to elevated temperatures (34-35.5 degrees C). Alternative complement activity and visceral AA concentrations were greater in fish fed diets with 218.5 mg AA/kg than in all other groups. The results indicate that the dietary requirement of AA for golden shiners increases in response to heat stress, and that the alternative complement activity (one index of immune competence) was strongly enhanced in fish fed a diet with approximately 10 times the amount of AA required to prevent deficiency signs.     

Influence of dietary ascorbic acid on plasma lipid levels in the rainbow trout

Rainbow trout maintained on ascorbic acid deficient and three grades of ascorbic acid supplemented diets (160--1280 mg ascorbic acid pr kg feed) for a period of 53 weeks, were studied for effects on plasma lipid levels. Fish fed the diet with no ascorbic acid manifested lethargy, lordosis, scoliosis, internal hemorrhages and low body weight. With regard to blood properties, ascorbic acid deficient fish had low hematocrit and high plasma levels of triglycerides and cholesterol but low level of free fatty acids. Plasma level of free fatty acids was low also in fish fed the diet containing the highest amount of ascorbic acid.     

Effect of L-ascorbic acid supplementation on the toxicity of pirimiphos-methyl to albino rats

The effect of L-ascorbic acid supplementation on Pirimiphos-methyl induced toxicity was studied in albino rats. Biochemical estimations were made in rats administered orally the insecticide at 100 and 200 mg/kg body weight with or without oral supplementation of L-ascorbic acid at 200 mg/kg b.w. The biochemical assessments included estimations of brain and plasma cholinesterases, levels of ascorbic acid in liver, kidney and adrenals, urinary levels of ascorbic acid and glucuronic acid. A lower degree of inhibition of the cholinesterases were evident in ascorbic acid supplemented rats. Marked elevation in urinary levels of ascorbic acid and glucuronic acid was observed in the insecticide treated rats. Results of this study suggests that L-ascorbic acid supplementation partially offsets Pirimiphos-methyl induced toxicity.     

Dietary selenium requirement of fingerling channel catfish

Two experiments were conducted in aquaria to determine the minimum dietary selenium requirement of fingerling channel catfish (Ictalurus punctatus). Casein-gelatin diets containing graded levels of supplemental selenium (as Na2SeO3) ranging from 0 to 15 mg/kg were fed to catfish for 15 weeks in experiment 1 to broadly define their selenium requirement and toxicity levels. Although growth of catfish was affected by dietary selenium level, significant differences in weight gain were not easily discernible due to variability among the groups of fish. Weight gain data generally indicated that the basal diet containing 0.06 mg Se/kg diet caused growth depression, and a supplemental selenium level of 15 mg/kg also caused a reduced growth response, which indicated selenium toxicity. Selenium concentrations in edible muscle tissue increased almost linearly with increasing dietary selenium levels. Liver and plasma selenium-dependent glutathione peroxidase (Se GSH-Px) activities indicated the selenium requirement of fingerling channel catfish was between 0.1 and 0.5 mg Se/kg diet. In experiment 2, casein-gelatin diets containing incremental levels of supplemental selenium were fed to catfish for 14 weeks to more precisely determine their minimum dietary selenium requirement. Growth data and liver and plasma Se GSH-Px activities indicated that the minimum selenium requirement of fingerling channel catfish fed adequate vitamin E was 0.25 mg Se/kg dry diet. Based on these data, it appears that selenium supplementation of commercial catfish feeds is warranted.     

Amelioration of oral copper toxicity in chicks by dietary additions of ascorbic acid, cysteine and zinc

Four experiments were conducted to evaluate the interrelationship of L-ascorbic acid, L-cysteine and Zn for amelioration of Cu toxicity in chicks. Chicks were fed a corn-soybean meal diet with 1,000 mg Cu (CuSO₄ · 5H₂O)/kg to produce Cu toxicity. Single dietary additions and two-way combinations of ascorbic acid (1,000 mg/kg), cysteine (0.5 g/100 g) and Zn (1,000 mg/kg) reduced liver Cu accumulation, with cysteine resulting in the largest response. Although supplemental Zn from ZnSO₄ · 7H₂O reduced liver Cu concentrations, it also reduced chick weight gain and food intake. Experiment 2 tested a range of cysteine and Zn levels to determine their effects on Cu toxicity in chicks. Supplemental Zn levels as low as 500 mg/kg reduced growth, but a cysteine level as low as 0.1 g/100 g increased chick weight gain and reduced liver Cu. Experiment 3 evaluated two Zn sources to determine if Zn source was affecting weight gain of chicks fed high Cu diets. There was a reduction in chick weight gain with 1,000 mg Zn/kg from Zn sulfate, but no reduction in weight gain with the same level of Zn from Zn oxide. In Experiment 4, 1,000 mg ascorbic acid/kg, 0.05 g/100 g cysteine and 1,000 mg Zn/kg from Zn oxide were tested in a 2 x 2 x 2 factorial. As in Experiment 1, ascorbic acid, cysteine and Zn were all effective in reducing liver Cu. The results suggested that L-cysteine was more effective than either L-ascorbate or Zn in ameliorating Cu toxicity, but a lower dose of cysteine together with pharmacologic additions of ascorbate and Zn (from ZnO) may be just as effective.     

Effect of vitamin C depletion on serum cholesterol and lipoprotein levels in ODS (od/od) rats unable to synthesize ascorbic acid

The effect of ascorbic acid deficiency on serum and liver cholesterol, phospholipid and triglyceride levels, serum lipoprotein levels and serum lipoprotein cholesterol levels were examined in male rats with a hereditary defect in ascorbic acid synthesis (ODS rats). Male homozygotes (od/od) and male rats of their parent strain (+/+) were each divided into four treatment groups and were fed vitamin C-deficient or vitamin C-replete diets containing either 0 or 0.5% cholesterol. During the 3-wk feeding-period the ODS (od/od) rats fed the vitamin C-deficient diet gradually decreased food intake, resulting in a lower body weight than that of od/od rats given ascorbic acid. The serum cholesterol level was significantly higher in the vitamin C-deficient od/od rats fed the cholesterol diet, and it tended to be higher in those fed the control (0% cholesterol) diet, whereas the liver lipid levels remained unchanged relative to those in od/od rats fed the vitamin C-replete diet. The serum very low density lipoprotein and high density lipoprotein (HDL) cholesterol levels were lower in od/od rats fed the vitamin C-deficient diet without cholesterol, but intermediate density lipoprotein and low density lipoprotein cholesterol levels were markedly higher in the vitamin C-deficient od/od rats than in od/od rats given ascorbic acid, regardless of dietary cholesterol level. The ratio of HDL2 cholesterol to HDL3 cholesterol was also higher in the vitamin C-deficient od/od rats. The parent strain of the od/od rats (+/+) showed no change due to vitamin C deficiency. These results suggest that vitamin C deficiency delays low density lipoprotein metabolism and produces hypercholesterolemia in male od/od rats.     

Dietary ascorbic acid depresses plasma and low density lipoprotein lipid peroxidation in genetically scorbutic rats.

The effects of dietary ascorbic acid on plasma lipoprotein and liver lipid peroxide concentrations were examined using ODS od/od rats with a genetic defect in the ability to synthesize ascorbic acid. ODS od/od rats were fed purified diets supplemented with 0 to 300 mg ascorbic acid/kg diet for 21 d. An ascorbic acid-free diet induced body weight loss, depleted ascorbic acid in the plasma and increased thiobarbituric acid-reactive substances in the plasma and liver as compared with rats fed ascorbic acid supplemented diets and with normal ODS +/+ rats fed the ascorbic acid-free diet. Increasing ascorbic acid concentration in the diet inhibited the development of these ascorbic acid deficiency symptoms in a dose-dependent manner. The dietary requirement of ascorbic acid to maintain normal body weight gain and plasma lipid peroxide concentrations was approximately 150 mg ascorbic acid/kg diet. On the other hand, even 300 mg ascorbic acid/kg diet was insufficient to maintain a hepatic concentration of ascorbic acid comparable to that in the liver of ODS +/+ rats. The lipid peroxide concentration in plasma LDL and liver was significantly elevated in ODS od/od rats fed the ascorbic acid-free diet. Supplementing the diet with 300 mg ascorbic acid/kg kept those concentrations within the normal ranges seen in the ODS +/+ rats.     

Hepatic ascorbic acid saturation is the most stringent response criterion for determining the vitamin C requirement of juvenile European sea bass (Dicentrarchus labrax)

Our main objective was to verify whether the dietary ascorbic acid (AA) requirement of juvenile European sea bass (Dicentrarchus labrax) varies as a function of different physiological needs. Practical diets with eight (0, 5, 10, 20, 40, 80, 160, 320 mg AA/kg diet) levels of ascorbic acid polyphosphate were fed to sea bass (mean weight: 0.7 g) for 15 wk. At the beginning and at the end of the feeding trial, tissues were sampled for vitamin C and hydroxyproline (HyPro) analysis. Dose-dependent responses of skin and whole body HyPro concentrations and hepatic AA concentration to dietary vitamin C levels were observed. Skin and whole body HyPro concentrations were low in sea bass fed AA-deficient diet, 217 and 15 nmol/g tissue, respectively. HyPro levels increased with increasing dietary levels, reaching plateaus of 297 and 45 nmol/g tissue in the skin and whole body at dietary vitamin C levels of at least 5 and 31 mg AA/kg. Hepatic AA level increased with increasing dietary levels, reaching a plateau of 474 pmol/g tissue in juveniles fed at least 121 mg of AA/kg. We concluded that hepatic AA saturation is the most stringent response criterion for determination of the vitamin C requirement in juvenile European sea bass.     

Effect of dietary n-3 fatty acids on weight gain and liver polar lipid fatty acid composition of fingerling channel catfish

A 10-wk experiment was conducted to determine the effect of supplementing a 5% tristearin basal diet with linoleic acid [18:2(n-6)], linolenic acid [18:3(n-3)], an n-3 highly unsaturated fatty acid (n-3 HUFA) mixture, cod liver oil, corn oil or linseed oil on growth and fatty acid composition of the liver polar lipid fraction of fingerling channel catfish (Ictalurus punctatus). The lowest weight gain was observed in fish fed the basal diet. Weight gain was improved by certain levels of supplemental n-3 fatty acids. Fish fed a diet containing 2% 18:3(n-3) grew at the same rate as fish fed a diet containing 2.5% cod liver oil plus 2.5% corn oil. The best growth rate was observed in fish fed diets containing either 5% cod liver oil or 5% linseed oil. Growth rate was depressed by supplementation with 4% 18:3(n-3) or 1.25% n-3 HUFA mix. No improvement in growth rate was observed with dietary 18:2(n-6). Dietary linolenate was converted to docosahexaenoic acid [22:6(n-3)]. The ratio of 20:3(n-9) to 22:6(n-3) of the fish showing good growth was less than 0.4. The data obtained in this experiment indicate that n-3 fatty acids are essential for channel catfish and that the 18:3(n-3) or n-3 HUFA dietary requirement is 1.0-2.0% or 0.5-0.75%, respectively.     

Megadose effects of vitamin C on vitamin B-12 status in the rat

Effects of ascorbic acid ingestion on the severity of vitamin B-12 deficiency were investigated by feeding weanling rats experimental diets containing 0-100 micrograms of vitamin B-12 activity per kg of diet, with or without 6.0 mg of ascorbic acid per ml supplied in drinking water for 15 wk. This daily consumption of up to 150 mg of ascorbic acid did not impair growth, but did result in significantly higher concentrations of ascorbic acid in plasma, liver, adrenal glands and feces. When rats were fed diets deficient or marginally deficient in vitamin B-12, liver concentrations of vitamin B-12 were markedly lower than in liver of rats fed adequate vitamin B-12. Ascorbic acid ingestion raised values significantly in the vitamin B-12-deficient diet group. Urinary methylmalonic acid was significantly elevated in the deficient rats. However, it was significantly reduced to more normal values by ascorbic acid in rats with both low and marginal vitamin B-12 status, as defined by dietary and liver concentrations of vitamin B-12 activity. Although coprophagy was not prevented, rats showed no increased consumption of feces with the higher ascorbic acid content. Thus, the results of this research indicate that vitamin C ingestion partially protects rats from vitamin B-12 deficiency.     

Dietary taurine alters ascorbic acid metabolism in rats fed diets containing polychlorinated biphenyls

The effect of dietary taurine on ascorbic acid metabolism and hepatic drug-metabolizing enzymes was investigated in rats fed diets containing polychlorinated biphenyls (PCB) to determine whether taurine has an adaptive and protective function in xenobiotic-treated animals. Young male Wistar rats (60 g) were fed diets containing 0 or 0.2 g/kg diet PCB with or without 30 g/kg diet of taurine for 14 d. The rats fed the PCB-containing diets had greater liver weight, higher ascorbic acid concentrations in the liver and spleen and greater hepatic cytochrome P-450 contents than control rats that were not treated with PCB (P < 0.01). In PCB-fed rats, urinary ascorbic acid excretion was enhanced, and serum cholesterol concentration (especially HDL-cholesterol) was significantly elevated compared with those in control rats. Dietary taurine significantly potentiated the increases in the urinary excretion of ascorbic acid and the rise in the levels of cytochrome P-450 which were caused by PCB treatment. On the other hand, the supplementation of taurine to control diet did not alter these variables. Taurine may enhance the hepatic drug-metabolizing systems, leading to the stimulation of the ascorbic acid metabolism in rats fed diets containing PCB.     

Antiscorbutic effect of dehydro-L-ascorbic acid in vitamin C-deficient guinea pigs

The antiscorbutic effect of dehydro-L-ascorbic acid (DAsA) was investigated in vitamin C-deficient guinea pigs. Male guinea pigs were fed vitamin C-deficient diets for 16 days to deplete body L-ascorbic acid (AsA) pools and then fed the deficient diet supplemented with DHA and/or AsA intraperitoneally for 14 days. During the repletion period, most of the animals injected with 0.5 mg DAsA/day developed scurvy, their body weights decreased and their mortality rate was higher than that of the other groups injected with 0.5 mg AsA/day or 5 mg DAsA/day. Injecting animals with 0.5 mg AsA/day resulted in the disappearance of the typical scorbutic symptoms and regaining of body weight. These data indicate that DAsA has considerably less antiscorbutic activity than AsA in vitamin C-deficient guinea pigs.     

Influence of dietary n-3 polyunsaturated fatty acids on plasma lipemic effect of vitamin B6 deficiency.

Since many connections exist between vitamin B6 and lipid metabolism, we aim to investigate the lipemic effect of different dietary intakes of polyunsaturated fatty acids in rats fed a vitamin B6 deficient diet. Diets were either vitamin B6 deficient (-B6) or vitamin B6 sufficient, pair-fed to the deficient group (PF) and ad libitum (N). The diets were combined with normal lipid (LC: soya bean-coconut-palm oils) and fish oil (FO: soya bean-fish oil). The fish oil diet with sufficient vitamin B6 content caused an increase in n-3 long chain polyunsaturated fatty acids and a decrease in arachidonic acid. In the -B6 group fed a normal lipid diet, the arachidonic acid percentage decreased and the linoleic acid percentage increased; in the -B6 group fed fish oil these changes in fatty acid composition, already consequent upon dietary intake of n-3 long chain polyunsaturated fatty acids, did not show further variations. In the dietary condition of vitamin B6 deficiency, plasma cholesterol content increased in rats fed a lipid control diet, whereas no hypocholesterolemic effect was observed in those fed a fish oil diet. Plasma triglyceride contents were not influenced by dietary lipid quality because, in all conditions, the lower food intake of the PF groups caused a decrease and vitamin B6 deficiency caused an elevation in triglyceride contents which reached those of the ad libitum groups. The study highlights the interaction between vitamin B6 and polyunsaturated fatty acids and the opportunity of dietary intake of fish oil to counterbalance some effects of vitamin B6 deficiency.     

Long-term effects of dietary polychlorinated biphenyl and high level of vitamin E on ascorbic acid and lipid metabolism in rats

Long-term feeding of purified diets containing (per kg diet) 100 mg of polychlorinated biphenyl (PCB) and 1000 mg of vitamin E (RRR-alpha-tocopheryl acetate) to male Wistar rats was carried out. Rats fed a diet containing PCB rapidly became hypercholesterolemic and maintained high cholesterol levels throughout the 240 d of the experiment. Rats fed a high dietary level of vitamin E plus PCB had higher serum cholesterol and lower liver cholesterol than rats fed a lower level of vitamin E plus PCB. In rats fed PCB, urinary excretion of ascorbic acid was higher than in rats not fed PCB. Urinary ascorbic acid was lower in rats fed high levels of vitamin E plus PCB than in those fed the normal levels of vitamin E plus PCB. Rats fed PCB had lower liver vitamin A storage and higher vitamin A in kidney than rats not fed PCB. This implies that a redistribution of vitamin A occurred in rats fed PCB. Histological observations revealed that central halves of the hepatic lobules of rats fed PCB showed distinct changes consisting of hypertrophy of hepatocytes in the perivenous region and accumulation of vacuoles (lipid droplets) in the cells in the remaining affected portion. Administration of a high dose of vitamin E could not ameliorate this lesion while the treatment depressed effectively the lipid peroxidation. This suggests that the lipid peroxidation was not responsible for the hepatic damage induced by PCB.     

Biological role of reactions of L-ascorbic acid with metals

L-ascorbic acid (H2Asc) is one of the basic vitamins, necessary to the normal growth and behaviour of organisms. The primary goal of this review is to present the chemical characteristics of this substance and to discussed its relation to various biological functions of vitamin C, mainly as a free radical scavenger. In presented work author analysed of same metals Cu(II), Zn(II), Cd(II), Hg(II), Pb(II) with L-ascorbic acid, showing preventive activity of vitamin C at exposure on metals.