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ORIGINAL ARTICLE
Year : 2016  |  Volume : 5  |  Issue : 4  |  Page : 247-252

Investigation on the phytochemicals present in the fruit peel of Carica papaya and evaluation of its antioxidant properties


1 Department of Chemistry, Loyola College, Chennai, Tamil Nadu, India
2 Department of Home Science, Women's Christian College, Chennai, Tamil Nadu, India

Date of Web Publication15-Nov-2016

Correspondence Address:
Sivapriya Thiyagarajan
Department of Home Science, Women's Christian College, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2278-344X.194127

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  Abstract 

Background: Plants have the major advantage of being the most treasured and cheaper alternative supplies of drugs. Phytochemicals in fruits and vegetables have gained increasing interest among consumers, and the scientific community as epidemiological studies has indicated that regular consumption of phytochemicals is related to a lower risk of noncommunicable diseases. Aim: The aim of the present study was to prepare extracts from the peel of indigenous fruit Carica papaya using five different solvents and to carry out qualitative and quantitative phytochemical analysis to establish the different classes of compounds present in the fruit peel and evaluate its antioxidant property by radical scavenging methods. Materials and Methods: Evaluate the antioxidant property of C. papaya peel by radical scavenging methods. Results: The various extracts revealed the presence of phytoconstituents such as phenols, flavonoids, and tannins in appreciable amounts and the antioxidant potential of papaya peel which can be used as a functional food to prevent and treat diseases.

Keywords: Antioxidants, fruit peel, functional foods, papaya fruit, phytochemicals


How to cite this article:
Lydia E, Riyazudin M, John S, Thiyagarajan S. Investigation on the phytochemicals present in the fruit peel of Carica papaya and evaluation of its antioxidant properties. Int J Health Allied Sci 2016;5:247-52

How to cite this URL:
Lydia E, Riyazudin M, John S, Thiyagarajan S. Investigation on the phytochemicals present in the fruit peel of Carica papaya and evaluation of its antioxidant properties. Int J Health Allied Sci [serial online] 2016 [cited 2019 Nov 12];5:247-52. Available from: http://www.ijhas.in/text.asp?2016/5/4/247/194127


  Introduction Top


The value of medicinal plants to the mankind is very well proven. India harbors about 15% (3000-3500) medicinal plants, out of 20,000 medicinal plants of the world. It is estimated that 70%-80% of the people worldwide rely chiefly on traditional health-care system and largely on herbal medicines.[1] Nature has been a source of medicinal plants for thousands of years, and a remarkable number of contemporary drugs have been secluded from natural sources. Various medicinal plants have been used for years in daily life as remedies to treat various diseases worldwide.[2]

In today's world, plants are gaining fascination owing to the fact that the herbal drugs are cost-effective, easily available, and with little or no side effects. Plant-based natural components can be procured from any part of the plant such as bark, leaves, flowers, fruits, roots, and seeds. Recently, the pursuit for the isolation of new compounds from medicinal plants has become an intriguing area of research. Plants with ethnopharmaceutical importance were being studied because of their healing properties as well as for their efficient antimicrobial, antidiabetic, and antioxidant properties.

Carica papaya belongs to the family of Caricaceae, and it originated from the southern part of Mexico. It is presently distributed over the world's tropical area. All parts of the papaya plant can be used as medicine that includes the fruit flesh, flowers, seeds, flowers, and peel. Many scientific investigations have been conducted to evaluate the biological activities of papaya fruit peel considered as a waste product.

The present work was attempted to investigate the phytochemical properties and evaluate the antioxidant activity of C. papaya peel by different radical scavenging methods. Papaya fruit peel which is disposed as waste by the fruit industry can be developed into a new functional food that will shield humanity from the clutch of several lethal disorders.


  Materials and Methods Top


The experimental design was carried as follows:

Collection and authentication of plant

C. papaya fruit was purchased from Koyambedu market, Chennai, India, and authenticated. The peels were manually separated from the remaining parts and dried at room temperature at 32°c for 1 day. The dried peel was subjected to grinding.

Sequential extraction

The dried powder of the peel was extracted sequentially[3] by Soxhlet apparatus, using different solvents depending on their polarities such as hexane, acetone, and ethanol. The dried powder weighing 800 g was percolated with solvents of varying polarity in 1000 ml conical flask. The percolation process was carried out for 48 h and the solvent was filtered using Whatman No. 41 filter paper. This process was repeated for all the solvents. The collected solvents were evaporated using a rotary evaporator (Super Fit, Rotavap, India).

Qualitative phytochemical analysis

The phytochemical screening was carried out using standard methods of analysis of carbohydrates, tannins, saponins, flavonoids, alkaloids, quinones, glycosides, cardiac glycosides, terpenoids, triterpenoids, coumarins, steroids, phytosteroids, phlobatannins, and anthraquinones.[4]

Test for carbohydrates

To 2 ml of peel extract, 1 ml of Molisch's reagent and few drops of concentrated sulfuric acid were added. The presence of purple or reddish color indicates the presence of carbohydrates.

Test for tannins

To 1 ml of peel extract, 2 ml of 5% ferric chloride was added. Formation of dark blue or greenish black indicates the presence of tannins.

Test for saponins

To 2 ml of peel extract, 2 ml of distilled water was added and shaken in a graduated cylinder for 15 min lengthwise. Formation of 1 cm layer of foam indicates the presence of saponins.

Test for flavonoids

To 2 ml of peel extract, 1 ml of 2N sodium hydroxide was added. The presence of yellow color indicates the presence of flavonoids.

Test for alkaloids

To 2 ml of peel extract, 2 ml of concentrated hydrochloric acid was added. Then, few drops of Mayer's reagent were added. The presence of green color or white precipitate indicates the presence of alkaloids.

Test for quinones

To 1 ml of peel extract, 1 ml of concentrated sulfuric acid was added. Formation of red color indicates the presence of quinones.

Test for glycosides

To 2 ml of peel extract, 3 ml of chloroform and 10% ammonia solution were added. Formation of pink color indicates the presence of glycosides.

Test for cardiac glycosides

To 0.5 ml of peel extract, 2 ml of glacial acetic acid and few drops of 5% ferric chloride were added. This was under-layered with 1 ml of concentrated sulfuric acid. Formation of brown ring at the interface indicates the presence of cardiac glycosides.

Test for terpenoids

To 0.5 ml of peel extract, 2 ml of chloroform was added and concentrated sulfuric acid was added carefully. Formation of red brown color at the interface indicates the presence of terpenoids.

Test for phenols

To 1 ml of peel extract, 2 ml of distilled water followed by few drops of 10% ferric chloride was added. Formation of blue or green color indicates the presence of phenols.

Test for coumarins

To 1 ml of peel extract, 1 ml of 10% NaOH was added. Formation of yellow color indicates the presence of coumarins.

Tests for steroids and phytosteroids

To 1 ml of peel extract, equal volume of chloroform is added and subjected with few drops of concentrated sulfuric acid; appearance of brown ring indicates the presence of steroids and appearance of bluish ring indicates the presence of phytosteroids.

Test for phlobatannins

To 1 ml of peel extract, few drops of 2% HCl were added. Appearance of red color precipitate indicates the presence of phlobatannins.

Tests for anthraquinones

To 1 ml of peel extract, few drops of 10% ammonia solution were added; appearance of pink color precipitate indicates the presence of anthraquinones.

Quantitative phytochemical analysis

Determination of total phenol content

The amount of total phenol content of different solvent extracts was determined by Folin-Ciocalteu's reagent method.[5] The various concentrations of the extract were made up with 900 μl of distilled water, and 0.5 ml of Folin-Ciocalteu's reagent was mixed and the mixture was incubated at room temperature for 15 min. Then, 4 ml of saturated sodium carbonate solution (0.7N) was added and further incubated for 30 min at room temperature, and the absorbance was measured at 765 nm using a ultraviolet (UV) spectrophotometer, against a blank sample. The calibration curve was made by preparing gallic acid (100-300 μg/ml) solution in distilled water. Total phenol content is expressed in terms of gallic acid equivalent (GAE) (mg/g of extracted compounds).

Determination of total tannin content

The amount of total tannin content of the peel extract was determined by Folin-Ciocalteu's reagent method.[6] The various concentrations of the extract were made up with 900 μl of distilled water, and 0.5 ml of Folin-Ciocalteu's reagent was mixed and the mixture was incubated at room temperature for 15 min. Then, 1 ml of saturated sodium carbonate solution (15%) was added and further incubated for 30 min at room temperature, and the absorbance was measured at 765 nm using a UV spectrophotometer, against a blank sample. The calibration curve was made by preparing tannic acid (20-60 μg/ml) solution in distilled water. Total tannin content is expressed in terms of tannic acid equivalent (mg/g of extracted compounds).

Determination of flavonoid content

The amount of flavonoid content of the peel extract was determined by the aluminum chloride colorimetric method.[7] The reaction mixture (3.0 ml) consisted of 1.0 ml of sample (1 mg/ml), 1.9 ml methanol, 0.5 ml of aluminum chloride (1.2%), and 0.1 ml potassium acetate (120 mM) and was incubated at room temperature for 30 min. The absorbance of the sample was measured at 415 nm using a digital spectrophotometer (Systronic, India), against a blank sample. The calibration curve was made by preparing a quercetin (10-30 μg/ml) solution in methanol. The flavonoid content is expressed in terms of standard quercetin equivalent (mg/g of extracted compounds).

Antioxidant assay

The antioxidant activity of the different solvent extracts of C. papaya peel was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and superoxide anion radical scavenging assays and isolated fractions were further evaluated by other antioxidant parameters such as ferric reducing antioxidant power (FRAP) assay, nitric oxide scavenging assay, and hydrogen peroxide scavenging assay.

Determination of 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity

The free radical scavenging activity of different solvent extracts was measured using DPPH by the method described by.[8] The reaction mixture 3.0 ml consisting of 1.0 ml methanol, 1.0 ml DPPH (0.3 mM), and 1.0 ml of solvent extracts of different concentrations of the screened plants and fractions of the extract was diluted by methanol, was incubated for 10 min, in dark, after which the absorbance was measured at 517 nm using UV-visible spectrophotometer (Elico, India), against a blank sample. Ascorbic acid (2-16 μg/ml) was used as positive control.[9] The percentage inhibition was determined by comparing the results of the test and the control. Percentage of inhibition was calculated using the formula:



Ferric reducing antioxidant power

The reducing ability of different solvent extracts and fractions of the C. papaya peel was determined by FRAP assay.[10] FRAP assay is based on the ability of antioxidants to reduce Fe3+ to Fe2+ in the presence of 2,4 6-tripyridyl-s-triazine (TPTZ), forming an intense blue Fe2+ TPTZ complex with an absorption maximum at 593 nm. This reaction is pH-dependent (optimum pH 3.6). 0.1 ml extract is added to 3.0 ml FRAP reagent (10 parts 300 mM sodium acetate buffer at pH 3.6, 1 part 10 mM TPTZ in 40 mM HCl, and 1 part 20 mM FeCl3 ) and the reaction mixture is incubated at 37°C for 10 min and then the absorbance was measured at 593 nm. FeSO4 (100-1000 μM/ml) was used as a positive control.[11] The antioxidant capacity based on the ability to reduce ferric ions of sample was calculated from the linear calibration curve and expressed as M FeSO4 equivalents per gram of extracted compound.


  Results Top


Qualitative phytochemical analysis

The preliminary screening of the fruit peel portrayed the presence of following phytochemicals represented in [Table 1].
Table 1: Preliminary phytochemical screening of peel extract


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Quantitative phytochemical analysis

Results for the quantitative analysis carried out on the sample of C. papaya are presented in [Table 2], [Table 3], [Table 4].
Table 2: Quantitative phytochemical estimation


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Table 3: Total flavonoid content


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Table 4: Total tannin content


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Total phenol estimation

Quantitative estimation of total phenolic contents [Table 2] reveals that aqueous extract of C. papaya peel was found to possess higher polyphenol content (4.84 mg GAE/g), followed by acetone extract (4.22 mg GAE/g) and ethanol extract (3.92 mg GAE/g).

Total flavonoid estimation

Flavonoids comprise the most common group of plant polyphenols and provide much of the flavor and color to fruits and vegetables. The six major subclasses of flavonoids include flavonols, flavonones, flavones, flavanols, flavan-3-ols, and isoflavones according to the positions of the substitutes present on the parent molecule. The flavonoids have aroused considerable interest recently because of their potential beneficial effects on human health. They have been reported to have antiviral, antiallergic, antiplatelet, anti-inflammatory, antitumor, and antioxidant activities.[12]

Results obtained from the estimation of total flavonoids [Table 3] contents reveal that acetone extract of C. papaya peel was found to possess higher polyphenols content (247.70 mg/mEq of quercetin), followed by aqueous extract (15.48/mEq of quercetin) and ethanol extract (0.83 mg/mEq of quercetin).

Total tannin estimation

Tannins are phenolic compounds of high molecular weight ranging from 500 to 3000 which are found in leaves, bark, wood, and bound to proteins that form insoluble or soluble tannin-protein complexes. They have been closely associated with plant defense mechanisms toward mammalian herbivores and insect. Tannins are divided into two main groups, according to their chemical structure and properties as hydrolysable tannins (HT) and condensed tannins (CT). HT are usually found in lower concentrations in plants than CTs.[13]

Results obtained from the estimation of total tannins contents [Table 4] reveal that acetone extract of C. papaya peel was found to possess higher polyphenols content (87.07 mg/mEq of tannic acid), followed by ethanol extract (41.29 mg/mEq of tannic acid) and aqueous extract (21.28 mg/mEq of tannic acid).

Antioxidant activity of Carica papaya peel powder

2,2-diphenyl-1-picrylhydrazyl assay

The molecule of 1,1-diphenyl-2-picrylhydrazyl (α,α-diphenyl-β-picrylhydrazyl; DPPH) is characterized as a stable free radical by virtue of the delocalization of the spare electron over the molecule as a whole, so that the molecules do not dimerize, as would be the case with most other free radicals. The delocalization also gives rise to the deep violet color, characterized by an absorption band in ethanol solution centered at about 520 nm. When a solution of DPPH is mixed with that of a substance that can donate a hydrogen atom, then this gives rise to the reduced form with the loss of this violet color (although there would be expected to be a residual pale yellow color from the picryl group still present). [Table 5] represents the results of DPPH radical scavenging activity of C. papaya peel.
Table 5: DPPH scavenging activity of Papaya extract and Ascorbic acid


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In the current study, acetone has more scavenging activity (86.5%) followed by ethanol (82.02%) and aqueous extract (31.68%).

Ferric reducing antioxidant power assay

The FRAP assay is presented as a novel method for assessing "antioxidant power." Ferric to ferrous ion reduction at low pH causes a colored ferrous-tripyridyltriazine complex to form. FRAP values are obtained by comparing the absorbance change at 593 nm in test reaction mixtures with those containing ferrous ions in known concentration. Absorbance changes are linear over a wide concentration range with antioxidant mixtures, including plasma, and with solutions containing one antioxidant in purified form.[13] [Table 6] depicts the results of FRAP assay. Results obtained from this study indicate that acetone has the highest radical scavenging with 1.388 g/M FeSO4 equivalents, followed by ethanol (0.5772 g/M FeSO4 equivalents) and aqueous extract (0.1168 g/M FeSO4 equivalent).
Table 6: Ferric reducing antioxidant power (FRAP) of Papaya Extract


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  Discussion Top


Phytochemicals (from the Greek word phyto, meaning plant) are biologically active, naturally occurring chemical compounds found in plants, which provide health benefits for humans further than those attributed to macronutrients and micronutrients.[14]

Pronounced as "fight-o-chemicals," phytochemicals fight to protect health. They can have complementary and overlapping mechanisms of action in the body, including antioxidant effects, modulation of detoxification enzymes, stimulation of the immune system, modulation of hormone metabolism, and antibacterial and antiviral effect.[15]

Phytochemical analysis has been regarded as one of the basic tools in the standardization process of plants and plant-based products as their presence or absence has a substantial influence on the quality and rationale of use. The presence of secondary metabolites such as phenols, tannins, flavonoids, alkaloids, quinones, saponins, glycosides, terpenes, coumarins, anthocyanins, phlobatannins, and steroids will help to assess the therapeutic efficacy of papaya peels.


  Conclusion Top


Nutraceuticals are the evolving class of natural products that diminishes the boundary between food and drugs. Only a product that has scientifically supported evidence can boom into a nutraceutical that could be effectively used by the consumers. The antioxidant properties determined by DPPH assay and FRAP assay will probe further way for exploration on the uniqueness of papaya peel which will certainly reveal a path of light for the development of functional foods from papaya.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Dong JG, Fernández-Maculet JC, Yang SF. Purification and characterization of 1-aminocyclopropane-1-carboxylate oxidase from apple fruit. Proc Natl Acad Sci U S A 1992;89:9789-93.  Back to cited text no. 13
    
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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[Pubmed] | [DOI]



 

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