Antimicrobial, Antioxidant and Cytotoxic Properties of Hypsizygus tessulatus Cultivated in Bangladesh
The aim of the present study was to evaluate certain biological properties of Hypsizygus tessulatus. Metabolic extract of submerged culture and mycelia mats of H. tessulatus mycelium was taken for investigating cytotoxic and antimicrobial activity using brine shrimp lethality bioassay and disc diffusion technique, respectively. Ethyl acetate extract showed higher antibacterial activity than chloroform extract against the Gram positive and Gram negative bacteria. The average zone of inhibition for ethyl acetate extract was in the range of 17-22 mm. Ethanol extract of mycelia mats of H. tessulatus showed significant antioxidant property using 1,1-diphenyl-2-pecrylhydrazyl (DPPH) scavenging assay along with total phenol content demonstrated moderate activity with IC50 value of 105 μg mL-1 and 36.45±1.754 g/100 g, respectively. The total antioxidant capacity of H. tessulatus was 442.61 mg equivalents of ascorbic acid. In brine shrimp lethality bioassay, LC50 values obtained from the best fit line slope were 7.36 and 10.63 μg mL-1 for ethyl acetate and chloroform extract, respectively. The study reveals that H. tessulatus mushroom has potential antimicrobial effect with moderate anticancer and antioxidant activity.
Received: August 05, 2011;
Accepted: November 30, 2011;
Published: January 12, 2012
Mushrooms have become attractive as a functional food and as a source for the
development of drugs and nutraceuticals (Barros et al.,
2007). Mushroom cultivation presents an economically important biotechnological
industry that has expanded markedly all over the world in the past few decades.
Major medicinal properties attributed to mushrooms include anticancer, antibiotic,
antiviral activities, immune response stimulating effects and blood lipid lowering
effects (Bobek and Galbavy, 2001). The add-value arising
from mushrooms are bioactive materials which lead to an increase in its consumption
and therefore, stimulate the commercialization of edible species. Mushrooms
also have been used extensively in traditional medicine for curing various types
of diseases such as viral infection, bacterial infection, cancer, tumor, inflammation,
cardiovascular diseases (Benedict and Brady, 1972;
Iwalokun et al., 2007). Both fruiting body and mycelium of different
mushrooms contain different compounds such as terpenoids, steroids, polyphenol,
polyketides, polyglucan, flavonoids, alkaloids, polysaccharides and dietary
fibers which exert several pharmacological activities (Breene,
1990). They are the rich source of antioxidants, antibiotics and antineuplastic
activity (Akyuz and Kirbag, 2009).
Hypsizygus tessulatus which is commonly known as Shimeji mushroom contains
glucans, niacin, vitamin B and D. Glucans are effective for cholesterol control,
immunity, constipation and weight loss. Niacin is effective for insomnia, mental
health and blood circulation. Vitamin B aids in immunity and weight loss, while
vitamin D is deemed to be effective against osteoporosis and anti-aging (Ikekawa,
2001). The previous name of this mushroom was Hypsizygus marmoreus
and it also contain different biologically active compounds like polysaccharides,
l-ergothioneine, sterols, ergosterol - provitamin D2 which have different
medicinal uses (Tsuchida et al., 1995; Saitoh
et al., 1997; Matsuzawa et al., 1998).
Hypsizygus tessulatus showed anti-platelet activity which may involved
in the suppression of intracellular calcium mobilization and integrin αIIbβ3
activation (Park et al., 2011). Hypsizygus
is a small genus of fungi that are widely distributed in north temperate regions.
The mushroom also has been reported to have beneficial effects on skin conditions.
Hypsizygus tessulatus is one of the valued species of traditional medicine.
Hypsizygus tessulatus is a small mushroom with light brown or white umbrella-
shaped caps. They are firm and crunchy in texture and they have a delicate mild,
sweet flavor (Waites et al., 2001).
The history of mushroom cultivation is not so long in Bangladesh; however,
mushroom consumption is increasing rapidly in this country due to cheap source
of dietary protein, carbohydrate, vitamins and minerals. Several species of
mushroom are being cultivated in Bangladesh among which some are of medicinal
importance (Amin and Alam, 2008). These are reishi,
enoki, oyster, shiitake, shimeji, milky, beech and nameko etc. (Imtiaj
and Rahman, 2008). The aim of this study was to evaluate the antibacterial,
cytotoxic and antioxidant properties of Hypsizygus tessulatus different
extract both from submerged culture and mycelia mat.
MATERIALS AND METHODS
Mushroom: Hypsizygus tessulatus were collected from National
Mushroom Development and Extension Centre, Dhaka. The mushroom was obtained
as potato dextrose agar slants. This mushroom was reported by the supplier to
grow at 25°C. The species was maintained on agar slants at 4°C and sub-cultured
every twelve weeks according to the suppliers recommendation.
Subculture and media composition: Three mycological media were used to evaluate the optimum growth of the organism. The organism was sub-cultured on potato dextrose agar or broth (PDA/PDB), malt-yeast extract (MY) and glucose-yeast extract peptone (GPY) media. Potato dextrose and glucose-yeast extract peptone media were sterilised at 121°C for 15 min whereas, malt-yeast extract medium was sterilised at 115°C for 10 min. All these media were purchased from Oxiod and Difco, UK.
Collection of study materials: The Hypsizygus tessulatus was culture in potato dextrose broth (PDB) medium, as maximum growth was observed in this medium (data not shown). The submerged culture was divided into two parts after 10 days of incubation at 28°C. The mycelia which formed a mat like structure was separated by filtration (Whatman No.1) and both parts were collected for further study. The isolated mats were air dried in an oven at 40°C before analysis and pulverized to fine powder by using motor and pestle. Dried mat (40 g) was extracted by stirring with 300 mL of ethanol at 30°C at 150 rpm for 24 h and filtering through Whatman No. 1 filter paper. The residue was then, extracted with two additional 300 mL of ethanol as described above. The combined ethanolic extract was then rotary evaporated at 40°C to dryness.
The culture filtrate (200 mL) from submerged culture was transferred to a separating funnel (500 mL) and extracted with chloroform and ethyl acetate, respectively. The extracts thus obtained were evaporated under reduced pressure in a rotary evaporator at 45°C to dryness and stored at 4°C for further use. These extracts were used for antimicrobial and cytotoxicity study on the other hand, mycelia mat extracts were used for antioxidant study. The reason for using two different parts for separate biological activity was to observe if both metabolite and mushroom itself is active in biological activity.
Antibacterial and antifungal screening: Both antibacterial and antifungal
activities of chloroform and ethyl acetate extract were observed by disc diffusion
assay (Bauer et al., 1966; Barry,
1976). A total of four Gram positive and three Gram negative bacteria (Table
1) were used in this antimicrobial screening. Chloroform and ethyl acetate
extract (400 and 500 μg disc-1) were prepared by dissolving
with chloroform and ethyl acetate, respectively. To compare the antibacterial
activity, kanamycin (30 μg disc-1) was used as standard antibiotic.
As a negative control, blank discs impregnated with solvents followed by drying
off were used. The antifungal activity of the chloroform and ethyl acetate extract
were tested against four pathogenic fungi (Candida albicans, Aspergillus
niger, Aspergillus flavus and Epidermophyton floccosum)
at a concentration of 400 μg disc-1. Potato Dextrose Agar (PDA)
media used for this purpose. The activity was determined after 72 h of incubation
at room temperature (37°C). Nystatin was used as standard at a concentration
of 30 μg disc-1.
Total phenolic content: Total phenolic content of Hypsizygus tessulatus
extract was measured by the method of Skerget et al.
(2005). In this method, Folin-Ciocalteu reagent acts as an oxidizing agent
and gallic acid as a standard. Briefly, 0.5 mL of extract solution (2 mg mL-1)
in water was taken and 2.5 mL of Folin-Ciocalteu reagent (diluted 10 times with
water) and 2.0 mL of sodium carbonate (7.5% w/v) solution were added. The mixture
was then incubated for 20 min at room temperature and after that period absorbance
was measured at 760 nm. Total phenolics were quantified by calibration curve
obtained from measuring the known concentrations of gallic acid (0-100 μg
mL-1). The phenolic contents of the sample were expressed as gm of
GAE (gallic acid equivalent)/100 gm of the dried extract.
DPPH radical scavenging assay: The antioxidant activity of the extracts
on the stable radical 1, 1-diphenyl;-2-picrylhydrazyl (DPPH) was determined
by the method developed by Feresin et al. (2002).
The 0.1 mL of mushroom ethanol extract, at various concentrations was added
to 3 mL of a 0.004% methanol solution of DPPH and was allowed to stand for 30
min for the reaction to occur. The absorbance of the resulting solution was
measured at 517 nm from this values the corresponding percentage of inhibitions
were calculated by using the following equation:
Where, Ablank is the absorbance of the control reaction (containing all reagents except the test sample) and Asample is the absorbance of sample/standard.
Extract concentration providing 50% inhibition (IC50) was calculated from the graph plotted I% versus concentration curve. The free radical scavenging activity was measured for different concentrations of sample and compared with standard (Ascorbic acid).
Determination of total antioxidant capacity (TAC): The total antioxidant
capacity was evaluated using the method described by Prieto
et al. (1999). Ascorbic acid was used as the standard antioxidant
drug. Three millilitter of the extract/standard drug (0.1, 0.3, 1 and 3 mg mL-1)
was placed in a test tube. The 0.3 mL of the reagent solution (0.6 M sulphuric
acid, 28 mM sodium phosphate and 4 mM ammonium molybdate) was then added and
the resulting mixture was incubated at 95°C for 90 min. After the mixture
has cooled to room temperature, the absorbance of each solution was measured
in triplicate using the UV-visible spectrophotometer at 695 nm against a blank.
The total antioxidant capacity was expressed as the number of gram equivalents
of ascorbic acid.
Cytotoxicity screening: For cytotoxicity screening, DMSO solutions of
the compounds were applied against Artemia salina for 24 h in vivo
assays (Meyer et al., 1982). The eggs of
the brine shrimp, Artemia salina, were collected from a local aquarium
shop and hatched for 48 h to mature shrimp called nauplii. The test samples
were prepared by dissolving them in DMSO (not more 3.8% NaCl in water) to attain
concentrations 400, 200, 100, 50, 25, 12.5, 6.25, 3.125, 1.563 and 0.781 μg
mL-1. A vial containing 50 μL DMSO diluted to 5 mL was used
as a control. Then 20 matured shrimps were applied to each of all experimental
vials and control vial. The number of the nauplii that died after 24 h was counted.
The findings were presented graphically by plotting log of concentration versus
percentage of mortality of nauplii from which LC50 was determined
by extrapolation and compared with the positive control using vincristine sulphate.
The assay was performed in duplicate and the result was calculated as an average
of two determinations.
Statistical analysis: Three replicates of each sample were used for statistical analysis and the values were reported as Mean±SEM. Correlation analysis of free radical scavenging activity versus total phenolic content and cytotoxicity were carried out using the correlation and regression program.
RESULTS AND DISCUSSION
Hypsizigus tessulatus has recently become a popular edible mushroom in Asia and has been cultivated by culture methods such as bottle culture and bag-culture. In the present study, we use submerged culture for growth instead of solid-state fermentation and as far as we concern this is the first report of biological activity of Hypsizygus tessulatus grown in submerged culture. This mushroom has been reported to exhibit many biological activities such as anti-tumor, antioxidant and antiproliferative activity when grown in solid culture.
The results of antibacterial activity are presented in Table
1. The fractions (chloroform and ethyl acetate) showed reasonable antibacterial
activity against pathogenic bacteria. However, ethyl acetate was more active
than chloroform extract against both Gram positive and Gram negative bacteria.
The antimicrobial activity increases gradually as dose is increased (Table
1). Ethyl acetate extract (500 μg disc-1) showed highest
activity towards every pathogen especially Shigella dysenteriae (22 mm)
and Staphylococcus aureus (21 mm) compare to standard.
|| Antibacterial activity of chloroform and ethyl acetate extract
of H. tessulatus metabolite
|Values are expressed as Mean±SEM (n = 3)
The chloroform fraction exhibited moderate activity towards most of the pathogen
and the highest zone of inhibition was observed against Bacillus subtilis
(12 mm) and Staphylococcus aureus (11 mm) at a concentration of 500
μg disc-1. There are several antimicrobial activity reported
from different mushrooms (Hearst et al., 2009)
however, the antibacterial activity of Hypsizygus tessulatus is obscure
in literature and hence direct comparison was not possible. The extracts have
no antifungal activity against the pathogenic fungi.
Oxidation is essential to many living organisms for the production of energy
to fuel biological processes. However, oxygen-centred free radicals and other
reactive oxygen species that are continuously produced in vivo, result
in cell death and tissue damage. Oxidative damage caused by free radicals may
be related to aging and diseases, such as atherosclerosis, diabetes, cancer
and cirrhosis (Halliwell and Gutteridge, 1984). Although,
almost all organisms possess antioxidant defence and repair systems that have
evolved to protect them against oxidative damage, these systems are insufficient
to prevent the damage entirely (Simic, 1988). However,
antioxidant supplements, or foods containing antioxidants, may be used to help
the human body reduce oxidative damage.
The model of scavenging DPPH radical is a widely used method to evaluate the
free radical scavenging activities of antioxidants. In the DPPH assay, the antioxidants
are able to reduce the stable DPPH radical (purple) to the non-radical form
DPPH-H (yellow). The DPPH scavenging activities of antioxidants are attributed
to their hydrogen donating abilities. In case of antioxidant screening of ethanol
extract of Hypsizygus tessulatus powdered mycelium has shown in Table
2. The IC50 value, defined as the concentration of antioxidant
required for 50% scavenging of DPPH radicals in this specified time period,
is a parameter widely used to measure antioxidant activity; a smaller IC50
value corresponds to a higher antioxidant activity of the plant extract. IC50
value of the ethanol extract was 105.0 μg mL-1. These values
state that H. tessulatus has moderate DPPH scavenging activity compared
to Ascorbic acid standard.
The content of the phenolic compounds in the ethanol extract was determined
through a linear gallic acid standard curve (y = 0.0008x + 0.2177, R2
= 0.8388). The higher the TPC value, the higher total phenolic content is present
in the extract. The total phenolic content of the extract occurred 36.45±1.754
gm of GAE/100 gm of dried extract which might be the evidence of showing antioxidant
property of that extract. Therefore, a positive correlation was seen between
the total phenolic content and antioxidant activity. The key role of phenolic
compounds as scavengers of free radicals is emphasized in several reports (Komali
et al., 1999). Poly-phenolic compounds have an important role in
stabilizing lipid oxidation and are associated with antioxidant activity (Gulcin
et al., 2003). This is in accordance with the fact that phenolic
compounds have potent free radical scavenging activity (Suzuki
et al., 1982; Velioglu et al., 1998).
It is suggested that poly-phenolic compounds have inhibitory effects on mutagenesis
and carcinogenesis in humans, when up to 1.0 g daily ingested from a diet rich
in fruits and vegetables (Tanaka et al., 1998).
The presence of several cytotoxic steroids (Zhao et al.,
2010) and flavonoids in the H. tessulatus was established previously.
This might be the cause of producing antioxidant effect of ethanol extract.
The Total antioxidant capacity of H. tessulatus expressed as the mg of
ascorbic acid/100 g of mushroom extract (mycelia mat) was determined by phosphomolybdenum
assay. The value was found in ethanolic extract was 442.61 mg equivalents of
In brine shrimp lethality bioassay, % mortality increased gradually with the
increase in concentration of the test samples. Table 3 and
4 show the result of brine shrimp lethality testing of various
extractives of H. tessulatus after 24 h of exposure to the samples and
the positive control, vincristine sulphate (VS). The LC50 values
were found 7.36, 10.63, 0.52 μg mL-1 for chloroform, ethyl acetate
and vincristine sulphate, respectively. In comparison to positive control (vincristine
sulphate), the cytotoxicity exhibited by chloroform extract was promising. Previous
study reveals that H. tessulatus found to give a significant increase
in life span when assayed using solid tumor. It has an inhibitory activity of
spontaneous tumor metastasis (Saitoh et al., 1997).
Another study stated that antioxidant activity of mice with tumor were significantly
higher than non tumerogenic mice (Matsuzawa et al.,
1998). Different types of polysaccharides has been reported from H. tessulatus
species which contained glucose, xylose, galactose and they showed potent antitumor
activity because such extracts induce the arrest of the cell cycle at the G0/G1
transition by means of induction of the expression of p53 and p21 proteins,
which inhibit the cyclinkinase complexes (CDK) (Ikekawa
et al., 1992).
|| IC50 value and total phenolic content of the sample
|The values of TPC and IC50 are expressed as Mean±SEM
(n = 3)
|| Effect of chloroform, ethyl acetate extract and positive
control vincristine sulphate (VS) on brine shrimp nauplii
|CH stands for chloroform, EA stands for ethyl acetate, VS
stands for vincristine sulphate
|| The result of cytotoxic activity of chloroform and ethyl
acetate extract on brine shrimp nauplii
Medicinal mushrooms used in the traditional medicine may be an interesting and largely unexplored source for the development of potential new compounds while the pragmatic medicinal properties have been attributed to mushrooms for thousands of years. But it is necessary to isolate the active principles and characterize their constituents for the benefit of human being. In conclusion, the metabolite and mycelia mat extracts of H. tessulatus demonstrated moderate antimicrobial, antioxidant activity, free radical scavenging activity as well as strong cytotoxic activity.
The authors wish to thank Mushroom Center Development Project, Dhaka, Bangladesh for the supply and identification of the species.
1: Akyuz, M. and S. Kirbag, 2009. Antimicrobial activity of Pleurotus eryngii var. ferulae grown on various agro-wastes. EurAsia J. BioSci., 3: 58-63.
2: Amin, S.M.R. and N. Alam, 2008. Study of mycelial growth of Cordyceps sinensis in different media, at different PH level and temperature. Bangladesh J. Mushroom, 2: 43-48.
3: Barros, L., M.J. Ferreira, B. Queiros, I.C.F.R. Ferreira and P. Baptista, 2007. Total phenols, ascorbic acid, β-carotene and lycopene in Portuguese wild edible mushrooms and their antioxidant activities. Food Chem., 103: 413-419.
CrossRef | Direct Link |
4: Benedict, R.G. and L.R. Brady, 1972. Antimicrobial activity of mushroom metabolites. J. Pharm. Sci., 61: 1820-1822.
Direct Link |
5: Bobek, P. and S. Galbavy, 2001. Effect of pleuran (β-glucan from Pleurotus ostreatus) on the antioxidant status of the organism and on dimethylhydrazine-induced precancerous lesions in rat colon. Br. J. Biomed. Sci., 58: 164-168.
6: Breene, W.M., 1990. Nutritional and medical value of specialty mushrooms. J. Food Protec., 53: 883-894.
7: Feresin, G.E., A. Tapia, G.R. Angel, C. Delporte, N.B. Erazo and G. Schmeda-Hirschmann, 2002. Free radical scavengers, anti-inflammatory and analgesic activity of Acaena magellanica. J. Pharm. Pharmacol., 54: 835-844.
8: Gulcin, I., M.E. Buyukokuroglu, M. Oktay and O.I. Kufrevioglu, 2003. Antioxidant and analgesic activities of turpentine of Pinus nigra Arn. subsp. pallsiana (Lamb.) Holmboe. J. Ethnopharmacol., 86: 51-58.
CrossRef | Direct Link |
9: Hearst, R., D. Nelson, G. McCollum, B.C. Millar and Y. Maeda et al., 2009. An examination of antibacterial and antifungal properties of constituents of Shiitake (Lentinula edodes) and oyster (Pleurotus ostreatus) mushrooms. Complement. Ther. Clin. Pract., 15: 5-7.
CrossRef | PubMed |
10: Ikekawa, T., H. Saitoh, W. Feng, H. Zhang, L. Li and T. Matsuzawa, 1992. Antitumour activity of Hypsizygus marmoreus. 1. Antitumour activity of extracts and polysaccharides. Chem. Pharm. Bull., 40: 1954-1957.
11: Ikekawa, T., 2001. Beneficial effects of edible and medicinal mushrooms on health care. Int. J. Med. Mushrooms, 3: 291-298.
12: Imtiaj, A. and S.A. Rahman, 2008. Economic viability of mushrooms cultivation to poverty reduction in Bangladesh. Trop. Subtrop. Agroecosyst., 8: 93-99.
13: Iwalokun, B.A., U.A. Usen, A.A. Otunba and D.K. Olukoya, 2007. Comparative phytochemical evaluation, antimicrobial and antioxidant properties of Pleurotus ostreatus. Afr. J. Biotechnol., 6: 1732-1739.
Direct Link |
14: Komali, A.S., Z. Zheng and K. Shetty, 1999. A mathematical model for the growth kinetics and synthesis of phenolics in oregano (Origanum vulgare) shoot cultures inoculated with Pseudomonas species. Process Biochem., 35: 227-235.
15: Matsuzawa, T., H. Saitoh, M. Sano, I. Tomita, M. Ohkawa and T. Ikekawa, 1998. Studies on antioxidant effects of Hypsizigus marmoreus. II. Effects of Hypsizigus marmoreus for antioxidant activities of tumor-bearing mice. Yakugaku Zasshi, 118: 476-481.
16: Meyer, B.N., N.R. Ferrigni, J.E. Putnam, L.B. Jacobsen, D.E. Nichols and J.L. McLaughlin, 1982. Brine shrimp: A convenient general bioassay for active plant constituents. Planta Med., 45: 31-34.
CrossRef | PubMed | Direct Link |
17: Park, J.Y., W.J. Oh, D.M. Kwak, M.G. Kim, G.S. Seo, S.B. Hong and M.H. Rhee, 2011. The anti-platelet activity of Hypsizygus marmoreus extract is involved in the suppression of intracellular calcium mobilization and integrin αIibβ3 activation. J. Med. Plants Res., 5: 2369-2377.
Direct Link |
18: Saitoh, H., W. Feng, T. Matsuzawa and T. Ikekawa, 1997. Antitumour activity of Hypsizygus marmoreus. 11. Preventive effect against lung metastasis of Lewin lung carcinoma. Yakugaku Zasshi, 117: 1006-1010.
19: Skerget, M., P. Kotnik, M. Hadolin, A.R. Hras, M. Simonic and Z. Knez, 2005. Phenols, proanthocyanidins, flavones and flavonols in some plant materials and their antioxidant activities. Food Chem., 89: 191-198.
CrossRef | Direct Link |
20: Suzuki, I., T. Yadomae, H. Yonekubo, M. Nishijima and T. Miyazaki, 1982. Antitumor activity of an immunomodulating material extracted from a fungus, Peziza vesiculosa. Chem. Pharm. Bull., 30: 1066-1068.
21: Tanaka, M., C.W. Kuei, Y. Nagashima and T. Taguchi, 1998. Application of antioxidative maillard reaction products from histidine and glucose to sardine products. Nippon Suisan Gakkaishi, 54: 1409-1414.
Direct Link |
22: Velioglu, Y.S., G. Mazza, L. Gao and B.D. Oomah, 1998. Antioxidant activity and total phenolics in selected fruits, vegetables and grain products. J. Agric. Food Chem., 46: 4113-4117.
CrossRef | Direct Link |
23: Waites, M.J., N.L. Morgan, J.S. Rockey and G. Higton, 2001. Industrial Microbiology: An Introduction. John Wiley and Sons, Oxford, ISBN: 9780632053070, pp: 169-170
24: Zhao, Y.Y., X. Chao, Y. Zhang, R.C. Lin and W.J. Sun, 2010. Cytotoxic steroids from Polyporus umbellatus. Planta Med., 76: 1755-1758.
25: Bauer, A.W., W.M.M. Kirby, J.C. Sherris and M. Turck, 1966. Antibiotic susceptibility testing by a standardized single disk method. Am. J. Clin. Pathol., 45: 493-496.
CrossRef | PubMed | Direct Link |
26: Barry, A.L., 1976. Principle and Practice of Microbiology. Lea and Fabager, Philadelphia
27: Halliwell, B. and J.M. Gutteridge, 1984. Oxygen toxicity, oxygen radicals, transition metals and disease. Biochem. J., 219: 1-14.
28: Simic, M.G., 1988. Mechanisms of inhibition of free-radical processes in mutagenesis and carcinogenesis. Mutat. Res./Funda. Molec. Mechan. Mutagen., 202: 377-386.
CrossRef | PubMed | Direct Link |
29: Tsuchida, K., Y. Aoyagi, S. Odani, T. Mita and M. Isemura, 1995. Isolation of a novel collagen-binding protein from the mushroom, Hypsizigus marmoreus, which inhibits the lewis lung carcinoma cell adhesion to type IV collagen. J. Biol. Chem., 270: 1481-1484.
CrossRef | Direct Link |
30: Prieto, P., M. Pineda and M. Aguilar, 1999. Spectrophotometric quantitation of antioxidant capacity through the formation of a phosphomolybdenum complex: Specific application to the determination of vitamin E. Anal. Biochem., 269: 337-341.
CrossRef | Direct Link |