|Year : 2013 | Volume
| Issue : 2 | Page : 126-130
Antimicrobial properties of coconut husk aqueous extract on cariogenic bacteria
Maria B Cyriac1, Vidya Pai2, Manjula Shantaram3, Maji Jose4
1 Department of Oral Pathology, Kannur Dental College, Anjarankandy, Kannur, Kerala, India
2 Department of Microbiology, Yenepoya Medical College, Mangalore, India
3 Department of Biochemistry, Yenepoya Medical College, Mangalore, India
4 Department of Oral Pathology, Yenepoya Dental College, Yenepoya University, Mangalore, India
|Date of Web Publication||13-Dec-2013|
Department of Oral Pathology, Yenepoya Dental College, Yenepoya University, Mangalore - 575 018, Karnataka
Source of Support: None, Conflict of Interest: None
Background and Objectives: The husk fibers of coconut (Cocos nucifera) are reported to be used by people of rural areas of South India for daily cleaning their teeth. As the beneficial effects of this plant material, with respect to antimicrobial properties against common cariogenic bacteria, are not scientifically proven, the present study was conducted. Materials and Methods: The husk of coconut was collected and aqueous extract was prepared and antimicrobial properties against common oral pathogens like Streptococcus mutans, Streptococcus salivarius, Streptococcus mitis, and Lactobacillus acidophilus were performed by agar well diffusion method. The values obtained were then subjected to statistical analysis using one way ANOVA and Tukey HSD. Results: Aqueous extract of coconut husk showed a concentration-dependent antimicrobial activity against different tested organisms with zone of inhibition ranging from 4.44 to 15.33 mms. However, the efficacy was less in comparison to chlorhexidine. Conclusion: Inhibitory action against cariogenic bacteria exhibited by aqueous extract of coconut husk indicate presence of highly effective active compounds in these extracts, which can be identified and incorporated into modern oral care systems for controlling dental caries.
Keywords: Antimicrobial activity, cocos nucifera, coconut husk, cariogenic bacteria
|How to cite this article:|
Cyriac MB, Pai V, Shantaram M, Jose M. Antimicrobial properties of coconut husk aqueous extract on cariogenic bacteria. Arch Med Health Sci 2013;1:126-30
|How to cite this URL:|
Cyriac MB, Pai V, Shantaram M, Jose M. Antimicrobial properties of coconut husk aqueous extract on cariogenic bacteria. Arch Med Health Sci [serial online] 2013 [cited 2017 May 29];1:126-30. Available from: http://www.amhsjournal.org/text.asp?2013/1/2/126/123024
| Introduction|| |
Despite extensive researches and inventions, oral diseases like dental caries continue to be most important global oral health problems. The causative organisms of dental caries are Gram-positive bacteria, primarily the Streptococcus mutans, Streptococcus salivarius, Streptococcus mitis, and Lactobacillus acidophilus, which metabolize sucrose to organic acids (mainly lactic acid) that dissolve the calcium phosphate in teeth, causing decalcification and eventually tooth decay.  The prevention strategy of these oral diseases mainly involves, controlling the oral pathogens by improving oral hygiene. Therefore, any agent that would reduce the microbial load has a significant role.
Herbal medicines are known to mankind, and medicinal plants have been used as traditional treatment for numerous human diseases for centuries in many parts of the world. In developing countries, where the availability of modern health services is limited, folk medicine, mainly based on plants are popular. The rich plant diversity of India is well utilized by the native communities for the treatment of oral diseases as well as for routine oral care practices. Many plants were reported to inhibit the growth of oral bacteria, particularly S. mutans and control plaque and thus prevent caries. Antibacterial chew sticks (meswak), which are plant based alternatives for oral health has been successfully promoted and they have been advocated by health agencies.  One of the common traditional practices followed by people of rural areas of Dakshina Kannada district of Karnataka, India is the use of husk of coconut as herbal 'chewing sticks' instead of plastic bristle brushes to maintain oral health and hygiene. 
The Coconut (C. nucifera Linn. belongs to Arecaceae family) is native to coastal areas of Southeast Asia. The husk covering the fruit is part of its pericarp. A thorough review of literature has revealed few studies on beneficial effects of husk of C. nucifera namely, antibacterial activity against Vibrio species  and S. aureus, antileishmanial  and antitumoral  properties. Studies conducted by Alviano et al have also suggested in vivo and in vitro analgesic and free radical scavenging properties of this plant material.  It is reported that certain plants like C. nucifera were used as teeth blackening agents by tribal population of Asia and suggested that this form of bodily inscription made a positive contribution to health status in these population due to the antimicrobial properties of this plant. 
Although coconut husks have been used for maintaining oral hygiene for many years, there is no scientific evidence for the beneficial effects of this plant material, with respect to antimicrobial properties against common cariogenic bacteria. Therefore, the present study was designed to find scientific evidence on valuable effects of this traditional practice.
| Materials and Methods|| |
The coconut husk was collected from local coconut growers. The husk fibers were washed with distilled water to remove dirt, cut into smaller pieces and air-dried for 21 days. The dried husk fiber was then blended using household electric blender. For the preparation of water extract, 100 gms of the plant powder was soaked in distilled water. After complete extraction (72 hours in shaker), the filtrate was concentrated to and was preserved at 4 0 C till further analysis. For antimicrobial analysis, different concentrations of the extracts i.e. 25 mg/ml, 100 mg/ml and 200 mg/ml were prepared by dissolving the concentrated extract in distilled water.
Test organisms were collected from carious cavities of affected teeth by scraping soft caries using excavator. After 48 hrs aerobic and anaerobic incubation in brain heart infusion broth, the samples were plated on a variety of selective and non-selective media. Colonies of different test organisms such as S. mutans, S. salivarius, S. mitis, and L. acidophilus were identified by Gram staining, colony morphology, and biochemical reactions.
The anti-bacterial screening was carried out using agar diffusion method described by Lino and Deogracious  with slight modifications. Freshly prepared inoculae were swabbed all over the surface of the agar plate using sterile cotton swab. Five wells of 6 mm diameter were bored in the medium with the help of sterile cork-borer having 6 mm diameter and were labeled properly and 50 μl of different concentrations of plant extract and same volume of positive and negative control were filled in the wells with the help of micropipette. 50μl of chlorhexidine (0.2%) was used as a positive control and the solvent control distilled water. After incubating the plates at 37°C for 24 hours, the zone of inhibition was measured using a scale. The mean and standard deviation of triplicates of various concentrations of plant extract were calculated and compared with chlorhexidine. The values obtained were then subjected to statistical analysis using one-way ANOVA and post-hoc analysis Tukey HSD.
To determine minimum inhibitory concentration (MIC), various dilutions of the extracts, which had anti-bacterial activity in the previous assay, were taken in sterile test tubes using nutrient broth as a diluents and a tube containing nutrient broth was taken as control. 50 μl of the standard culture inoculum was added to each test tube, except the control tube. All tubes were incubated at 37°C for 24 hours and then examined for growth by observing turbidity. 10μl of bacterial culture was pipetted from the mixture obtained in the determination of MIC tubes, which did not show any growth and sub-cultured onto Muller Hinton agar and incubated at 37 o C for 24 hours. After incubation, the concentration at which there was no single colony of bacteria was taken as minimum bactericidal concentration (MBC). 
| Results|| |
The zone of inhibition observed is shown in [Figure 1]. The aqueous extract of coconut husk at 25 mg/ml concentration did not express any zone of inhibition when tested on cariogenic organisms. But, a statistically significant, concentration-dependent increase in activity was noted from 100 mg/ml to 200mg/ml [Figure 2]. However, the zone of inhibition was less compared to the positive control, chlorhexidine. Statistical analysis using one-way ANOVA revealed significant difference within the groups [Table 1]. Post-Hoc analysis using Tukey HSD exhibited a statistically significant difference between the groups [Table 2]. The minimum inhibitory concentration and minimum bactericidal concentration are shown in [Table 3].
|Figure 1: Effect of aqueous extract of coconut husk on different test organisms|
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|Figure 2: Consolidated graph showing a concentration-dependent increase in zone of inhibition of aqueous coconut husk extract|
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|Table 1 :Comparison of zone of inhibition produced by coconut husk aqueous extract in different concentration with Chlorhexidine |
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|Table 2 : Multiple Comparisons of Zone of inhibition between different groups |
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|Table 3 : MIC and MIB in mg/ml of aqueous extracts of coconut husk extract against different test organisms |
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| Discussion|| |
Essential oils and extracts have been used for thousands of years by mankind as natural therapies. Plant extracts are potential sources of novel antimicrobial compounds, especially against bacterial pathogens.  Traditional methods of dental and oral care are still practiced by some people residing in rural areas. As the modern methods of oral hygiene measures gained importance, traditional knowledge is slowly vanishing away, and now they are not part of everyday life. Use of leaves and fibers of some plants have been found to be highly effective for prevention and healing of diseases of gum, oral mucosal diseases, and tooth decay.  However, all these beneficial effects have to be scientifically validated and proved. In the present study, we have evaluated antimicrobial properties of coconut husk, which is used commonly for cleaning the teeth by people residing in rural areas of south India.
For evaluating the antimicrobial properties, the effect of various concentrations of aqueous extract of coconut husk was tested on major cariogenic organisms such as S. mutans, S. salivarius, S. mitis, and L. acidophilus. Although lesser in extent than chlorhexidine, the extracts at concentration of 100 mg/ml and 200 mg/ml showed inhibitory action on tested cariogenic bacteria. This is a promising observation, indicating presence of effective antimicrobial components in this plant material.
The beneficial medicinal effects of plant materials including the antibacterial activity typically result from the secondary products present in the plant, although it is usually not attributed to a single compound but a combination of the metabolites.  The exact mechanism by which the active components of the plant materials contribute to anti-bacterial activity is not known. One of the mechanisms suggested is hydrophobic activities, which enable them to partition the lipids of the bacterial cell membrane and mitochondria, disturbing the cell structures and rendering them more permeable. This result in extensive leakage from bacterial cells or the exit of critical molecules and ions will lead to death.  Tannins present in the plant extracts also have an astringent effect on the mucous membrane, and they form a layer over enamel, thus providing protection against dental caries.  Phytochemical screening of C. nucifera conducted by Alviano et al. has reported that this plant material is rich in alkaloids, flavonoids, catechin, and epicatechin together with condensed tannins, which confers on its potent antimicrobial properties. 
The inhibition produced by the plant extracts against particular organism depends upon various extrinsic and intrinsic parameters. Variable diffusability of plant extract in agar medium may also influence zone of inhibition. In case of decreased diffusability, the antibacterial property may not demonstrate as zone of inhibition in proportion to its efficacy.  Therefore, MIC and MBC value, the lowest concentration of antibacterial substance required to produce a sterile culture, has also been computed here. In this study, the MIC and MBC values ranged from 50 mg/ml to 100 mg/ml.
Our study has confirmed the beneficial effects of coconut husk with antimicrobial effect on cariogenic bacteria. Therefore, we propose that when this plant material is used for cleaning the teeth, two-fold benefits are obtained, i.e. mechanical cleansing by fibrous component and antimicrobial effect of chemical constituent. The concentration-dependent activity indicates a possibility of obtaining zone of inhibition comparable to chlorhexidine, at a higher concentration of extract. As earlier reports indicates that alcohol is a better solvent capable of extracting most of active components, further studies are recommended using alcoholic extracts, which may reveal more beneficial effects of so-called "tree of heaven / tree of life." ,
From the results obtained, we would like to conclude that traditional oral care practices, though scientifically not proven, have time-tested valuable effects. Identification and isolation of active antimicrobial compounds of this plant material may open a new path to fight against dental caries, because these may be incorporated in to modern oral care systems such as tooth pastes or mouth washes. This may provide the possibility of combining the benefits of traditional and modern practices to offer maximum benefit to mankind for better oral health.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]