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ORIGINAL ARTICLE
Year : 2021 | Volume
: 10
| Issue : 4 | Page : 275-279
Analysis of nutrients, phytochemicals, antioxidant and antimicrobial activity of corn silk extract (Zea mays L. Stigma)
H Rajeshwari1, T Sivapriya2
1 Department of Food Science, Nutrition and Dietetics, Hindustan Institute of Technology and Science, Chennai, Tamil Nadu, India
2 Department of Food Technology, Hindustan Institute of Technology and Science, Chennai, Tamil Nadu, India
Correspondence Address:
Dr. T Sivapriya
Department of Food Technology, Hindustan Institute of Technology and Science, Chennai, Tamilnadu
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/ijhas.IJHAS_148_20
OBJECTIVE: The objective of the study is to estimate the nutrients, phytochemicals, antioxidant, and antimicrobial activity of Zea mays L. (Poaceae) Stigma maydis.
MATERIALS AND METHODS: Aqueous extract of Zea mays L. (Poaceae) Stigma maydis was used for nutrient, phytochemical antioxidant, and antimicrobial analysis. Total carbohydrate, protein, fat, fiber, and energy were assessed according to British Pharmacopeia. Phytochemicals were screened by Trease and Evans method. Antioxidant assay was done by ferric reducing antioxidant power (FRAP) and 1, 1-diphenyl 2-picrylhydrazyl (DPPH) methods. Antimicrobial activity was determined by the agar well-diffusion method.
RESULTS: The amount of carbohydrate, protein, fat, fiber, and energy present Zea mays L.(Poaceae) Stigma maydis was 6.12 g, 20.2 g, 0, 1.35 g, and 117.3 kilo calories, respectively. Preliminary phytochemical assay established the presence of phenols, flavonoids, tannins, alkaloids, saponins, terpenoids, glycosides, and steroids. The antioxidant activity was estimated as 76.75% at 700 nm by FRAP assay and 65.19% at 517 nm by DPPH assay. The zone of inhibition was found to be 1.5 mm against Escherichia coli.
CONCLUSION: Zea mays L. (Poaceae) Stigma maydis can be used as a functional food to eradicate communicable as well as noncommunicable diseases due to its antioxidant and antimicrobial activity. It can be incorporated into food products for effective usage.
Keywords: Antimicrobial activity, antioxidant, nutrients, phytochemicals, Zea mays L.(Poaceae) Stigma maydis
Zea mays stigma (Corn silk) is the name of the long styles and stigmas on flower pistils. The stigmas are fine and soft, yellowish to green threads of female flowers. Corn silk has been seen treated as waste and often underutilized. Maize (Zea mays L.), belonging to family Poaceae, is the third important cereal crop worldwide. It is used as human food, animal feed, and raw material for manufacturing a number of industrial products and is considered a potential valuable biofuel and forage crop. Corn silk has also been used in many parts of the world for herb treatment of hypertension, tumor, hyperglycemia, hepatitis, cystitis, gout, kidney stones, diabetes nephritis, and prostatitis. By evidence-based scientific research, if the nutrients, phytochemicals, and active constituents present in it are determined, corn silk can be used in the preparation of functional foods and nutraceuticals which are much essential at this juncture.[1]
Corn silk consisted of 9.65% moisture, 17.6% protein, 0.29% fat, 3.91% ash, and 40% dietary fiber. Corn silk is an excellent source of many bioactive compounds such as volatile oils, steroids, alkaloids, and natural antioxidants such as flavonoids, and other phenolic compounds with beneficial effects on human health and minerals such as Ca, K, Mg, Mn, and Zn are presented in corn silk.[2] Previous toxicological study on crude aqueous extract of corn silk has proven that it did not show any toxic effect on the hematopoietic systems of Wistar rats.[3]
In the traditional medicine system, corn silk has been used in several areas of the world including the United States, China, France, and Turkey. The extracts of corn silk contain good quantity of a type of flavonoid, maysin, which is specific to corn. Maysin is a flavone glycoside encompassing luteolin, a biologically active agent known for its antioxidant and anticancer potential. The high maysin corn silk extracts have been proven to be beneficial in reducing body weight and fat deposition in C57BL/6J mice.[4] Ethanolic maize silk extract of corn silk has also shown protective effects on radiation-induced oxidative stress. The administration of aqueous extract of corn silk at 100–400 mg/kg between on hematological and lipid parameters in rats and male ICR mice treated for 4 weeks at 500 mg/kg between of corn silk extracts has been found nontoxic.[5]
The oral administration of the aqueous extract to malaria-infected animals for 5 days significantly reduced the parasitemia level indicating the antimalarial property of corn silk extract. This antimalarial potency of corn silk extract could be associated with the presence of alkaloids and phenols acting by inhibition of phosphodiesterase and known as inhibitors of the fatty acid biosynthesis pathway needed for the successful growth of malaria parasite.[6]
The treatment of infected mice with the corn silk extract significantly protected infected mice from the immune cells and platelet dysregulation, through the presence of alkaloids, tannins, and phenolic components that act by detoxification of enzymes and modulating effect on the immune system.[7]
There is scanty information regarding the systematic evaluation of phytochemicals and antioxidant activity in corn silk, and the information on different corn types and varieties is still lacking. Therefore, the objectives of this study were to evaluate nutrient contents, phytochemicals, their antioxidant, and antimicrobial activity.
Materials and MethodsAnalysis of nutrients, phytochemicals, antioxidant, and antimicrobial activity of corn silk extract (Zea Mays L. Stigma) has been approved by the Independent Human Ethics Committee (IHEC) (Protocol No. SDNBVC/HSC/IHEC/2019/01), conducted by the Department of Home Science, SDNB Vaishnav College for Women, Chennai, Tamil Nadu, India. The experimental design was carried out to find the proximate principles, phytochemicals, antioxidant assay, and antimicrobial assay. The study was conducted in Armats lab, Guindy, Chennai. Most of the chemicals used for phytochemical screening were purchased from Biosar, India. For proximate principle, antioxidant, and microbial study, analytically graded chemicals were purchased.
Fresh and matured corns were collected from the local market. Aqueous extract was used for qualitative analysis, and the aqueous extract of corn silk was extracted by the method of extraction of technologies for medicinal and aromatic plants, 1st edition described by Handa et al.[8] Corn silk was removed from them and stored in the airtight package at room temperature for further analysis.
Nutrient analysis
The nutrient content of corn silk extract with regard to carbohydrate, protein, fat, fiber, and energy has been assessed. Total carbohydrate content was determined by gravimetry method.[8] The nitrogen content of corn silk was estimated as per Evans and Trease method.[9] Protein content was calculated as nitrogen content ×6.25. Fat content of corn silk was analyzed as per British Pharmacopeia 2018. Dietary fiber by means of any official methods adopted by Horwitz and Latimer.[10] Total energy was evaluated.[11] The energy is calculated by the formula as follows: Energy = Grams of carbohydrate and protein total ×4 + Fat in g ×9.
Qualitative phytochemical analysis
The different qualitative analysis was carried out to test the presence of alkaloids, phenols, flavonoids, steroids, glycosides, saponins, tannins, and terpenoids in corn silk extract. The method recommended by Yen and Chen[12] was followed.
Test for alkaloids
The solvent-free extract (50 mg) of corn silk was stirred with 2 ml of dilute hydrochloric acid (1 ml HCL + 1 ml H2o) and saturated picric acid was added. Yellow precipitate indicates positive for alkaloids.
Test for phenolic compound
It is ferric chloride test. The corn silk extract (50 mg) was dissolved in 5 ml of distilled water. To this, few drops of neutral 5% ferric chloride solution were added. A dark green color indicated the presence of phenol.
Test for glycosides
To 2 ml of corn silk filtrate, sodium nitroprusside (half pellet) and 35 drops of pyridine were added. Blood red color indicates the presence of glycosides.
Test for terpenoids
Corn silk extract was added in 2 ml of chloroform. Concentrated H2S04 (3 ml) was carefully added to form a layer. A reddish-brown coloration of the interface indicates the presence of terpenoids.
Test for flavonoids
0.5 g of corn silk extract was dissolved in 5 ml of distilled water, followed by the addition of half pellet of sodium hydroxide. A yellow/red precipitate formation within short period showed positive presence of flavonoids.
Test for tannins
Corn silk extract and few drops of 0.1% ferric chloride were added and observed for brownish green or a blue-black coloration.
Test for saponins
It is foam test. The corn silk extract (50 mg) was diluted with 5 ml distilled water. The suspension was shaken in a graduated cylinder for 15 min. A 2 cm layer of foam indicated the presence of saponins.
Test for steroids
To the corn silk extract, few drops of concentrated sulfuric acid, followed by acetic anhydride, resulting in brown to red color indicate the presence for steroids.
Determination of antioxidant activity
Determination of 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging activity
The antioxidant activity of corn silk extract was measured based on the sw, 1-diphenyl 2-picrylhydrazyl (DPPH) free radical scavenging activity. One milliliter of 0.1 mm DPPH solution in methanol was mixed with 1 ml of various concentrations (20–120 μg/ml) of essential oil. The mixture was then allowed to stand for 30 min incubation in dark. One milliliter methanol mixed with 1 ml DPPH solution was used as the control. The decrease in absorbance was measured using ultraviolet-visible spectrophotometer at 517 nm. Ascorbic acid was used as the standard reference.
The percentage of inhibition was calculated using the following formula:
% of DPPH˙ radical inhibition = (Control – Sample/control ×100).
Ferric reducing antioxidant power
The reducing power of the corn silk extract was determined by the modified method.[12] One milliliter of corn silk extract of different concentrations (20–120 μg/ml) was mixed with 1 ml of phosphate buffer (0.2 M, pH 6.6) and 1 ml of 1% (w/v) potassium ferricyanide (K3Fe [CN]6) solution. The mixture was then incubated at 50°C for 20 min in water bath. One milliliter of 10% (w/v) trichloroacetic acid was added to each mixture followed by 1 ml mixture of 0.1% (w/v) FeCl3 solution and shaken well. The absorbance was measured at 700 nm using spectrophotometer. Ascorbic acid was used as the standard reference. The percentage of inhibition was calculated using the following formula:
% of Fe3 + reduction = (Sample – Control/sample ×100).
Evaluation of antimicrobial activity-agar well-diffusion method
Antibacterial activities of the corn silk extracts were tested using agar well-diffusion method. The bacterial isolates were subcultured in peptone water. After 24 h, the solutions got turbid and using spectrophotometer, the turbid solutions were analyzed and compared with that of standard 0.5 McFarland solutions. Using sterile cotton board, the suspensions were stricken on top of the previously sterilized petri plates with solidified media and were allowed to dry for 15 min. Five wells were punched using sterile cork borer of 6 mm size. To test the sensitivity properties of the extract, half dilutions of 600, 300, and 150 mg/ml were prepared from stock solution using dimethyl sulfoxide (DMSO) as diluents. Each well was filled with 0.5 ml of the different dilutions. A standard antibiotic ciprofloxacin (30 μg/ml) was used as positive control, while DMSO served as negative control. This was done to check for sterility and any growth inhibitory potential of the solvent. The plates were kept for 1 h at room temperature to allow diffusion of the extract to take place and then incubated aerobically at 37°C for 24 h. The zones of inhibition produced by Escherichia More Details coli were measured in (mm) across the diameter.
ResultsThe proximate nutrient analysis of corn silk extract revealed [Table 1] the nutritional composition of carbohydrate, protein, fat, fiber, and total energy.
The amount of carbohydrate present in corn silk extract was 6.121 g/100 g of corn silk. The protein content was calculated from the nitrogen content by times of 6.25. The protein content of corn silk extract was found to be 20.23 g/100 g of corn silk. The fat content was nil in corn silk, and hence, it can be used as a supplement in the treatment of liver diseases and cardiovascular disease. The fiber present in corn silk extract was 1.345 g/100 g. The total amount of energy present in 100 g of corn silk is 117.3 kilocalories (approximately).
[Table 2] indicates the results of the qualitative phytochemical assay. Preliminary phytochemical assay on the extract of corn silk extract established the presence of phenols, flavonoids, tannins, alkaloids, saponins, terpenoids, glycosides, and steroids.
Antioxidant assay
The results for the DPPH assay of varying concentrations of corn silk extract are given in [Table 3].
Table 3: Antioxidant activity of corn silk extract using 2, 2-diphenyl -1- picrylhydrazyl assay[Table 3] illustrates the results of the antioxidant power of corn silk extract using DPPH assay. The radical scavenging increases with increase in the concentration of corn silk extract. The result obtained from this study indicates that the aqueous extract of the corn silk has the highest DPPH radical activity. The scavenging effect of the standard on the DPPH radical increased in the order of 12.41%, 15.28%, 27.07%, 36.46%, 50.82%, and 65.19%, respectively.
The result obtained from [Table 4] indicates that the corn silk extract has the highest radical scavenging activity. The scavenging activity increases in order of 7.93%, 62.69%, 69.63%, 74.49%, 75.9%, and 76.75%, respectively. The ferric reducing antioxidant power (FRAP) of corn silk increases with the increase of concentration.
Antimicrobial activity
The result indicates that the corn silk extract possesses reasonable antimicrobial activity against bacteria E. coli by demonstrating zone of inhibition of 1.5 mm. It can be concluded from the result that corn silk has the potential to be used in curing diseases caused by E. coli. When compared to ciprofloxacin, the zone of inhibition of corn silk was less.
DiscussionCorn silk is considered as a waste by product of maize and usually discarded. Corn silk can be used effectively as a functional food after determining the nutrients, the toxins present in it, and the daily acceptable intake. It can be incorporated into various food products to enrich the value of the product after analyzing the nutrients present in it [Table 5].
Contrary to the results of our study, the amount of carbohydrate and protein present was 27.8 g and 5.7 g, respectively, in a research carried out by Solihah et al.[13] The study by Jun et al.[14] showed the nutritional composition of the matured corn silk. Carbohydrate and protein percentage of matured corn silk is 29.74% and 8.95%, respectively. The lipid and fiber content of matured corn silk is 0.66% and 51.24%, respectively. The results of the present study are contrary to the study which showed a higher protein than the carbohydrate content. The chemical compositions of a plant product like protein are more influenced by genetic traits, and there are possibilities to vary from plant to plant and from cob to cob and region to region depending on the fertility of soil. The amount of fat is negligible, 0.36 g and it is similar to the present study.
The study conducted by Stella et al.[15] showed the presence of phytochemicals such as phenols, flavonoids, tannins, phlobatannin, alkaloids, saponins, and cardiac glycosides in aqueous extract of corn silk. These results are similar to the present study and showed the presence of bioactive compounds found in Zea mays hair. Zea mays hair can be used to develop functional foods which contribute to various pharmaceutical responses. The results indicate that corn silk is rich in phytochemicals, which may be responsible for its medicinal property.
The study concluded by Liu et al.[16] stated that flavonoids that are present in corn silk are the major constituent that scavenges the DPPH radical, due to the presence of the hydroxyl groups in its structure and their electron-donating ability. The study showed the correlations between total phenolic content and free-radical scavenging activity. The corn silk showed the greater FRAP with the content of total phenolic compound and total flavonoids which showed that the flavonoids and phenolic present in corn silk were main constituents for exhibiting higher ferric reducing power.[17]
The study conducted by Tian et al.[18] to demonstrate the antimicrobial activity of corn silk against various diseases causing microorganism such as Pseudomonas aeruginosa, Salmonella More Details typhi, E. coli, Klebsiella pneumonia, and Staphylococcus aureus 
possessed reasonable activity against Gram-positive and Gram-negative bacteria. Based on the study conducted by Ponce et al.[19] and his guidelines to classify sensitivity for antimicrobial activity, corn silk has the potential antimicrobial activity in curing infections.
The result of the present study showed the amount of macronutrients, and phytonutrients present in corn silk extract. The protein content was comparatively high and fat percentage was nil. The phytochemical composition of corn silk extract revealed the presence of phenols, flavonoids, tannins, alkaloids, saponins, terpenoids, glycosides, and steroids. This shows that the corn silk had great phytochemical activity and it also possessed positive antioxidant capacity. Corn silk extract also possesses considerable antimicrobial activity. With this excellent profile of corn silk, it can be endorsed that corn silk is an excellent functional food ingredient or a nutraceutical supplement. It can be incorporated in food stuffs such as patties, biscuits, cakes, and sauces to improve the nutrient as well as immune-boosting capacity of the food.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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