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Research Article

Screening of Antibiotic Resistant Inhibitors from Indian Traditional Medicinal Plants Against Streptococcus mutans

T. Francis Xavier and P. Vijayalakshmi
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Aqueous and ethanolic extracts of ten plants used in traditional Indian medicine for treatment of an infectious nature were screened for antibacterial activity by disc diffusion method against Streptococcus mutans. Among them the ethanol extracts of Allium sativum bulb exhibited high degree of inhibition followed by Azadirachta indica leaf extracts. The aqueous extracts of plants did not show any antibacterial activity against Streptococcus mutans.

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T. Francis Xavier and P. Vijayalakshmi , 2007. Screening of Antibiotic Resistant Inhibitors from Indian Traditional Medicinal Plants Against Streptococcus mutans. Journal of Plant Sciences, 2: 370-373.

DOI: 10.3923/jps.2007.370.373



Human infections caused by Gram-positive bacterial pathogens are increasingly difficult to treat, predominantly due to emergence of drug resistant bacterial strains. One such Gram-positive bacterial organism is Streptococcus mutans causing dental caries in humans (Hamada and Slade, 1980; Akhtar and Bhakuni, 2004). This bacterium adheres firmly to the smooth tooth surfaces and produces sticky water insoluble dextran from dietary sucrose, forming plaque which facilitates the accumulation of microorganisms. Streptococcus mutans and other organisms in the plaque produce organic acids such as lactic acid that gradually destroy the enamel and form a cavity (Bhattacharya et al., 2003). Elimination of Streptococcus mutans would reduce the incidence of dental caries. Extensive efforts have been made to find an active agent against dental caries. However Streptococcus mutans was found to be resistant to many of the antibacterial agents viz., Penicillin, amoxicillin, cefuroxin, tetracycline and erythromycin (Jarvinen et al., 1993; Bhattacharya et al., 2003). In addition they may lead to side effects including gastrointestinal problems (Craig, 1998). These drawbacks justifies further research and development of natural antimicrobial agents that are effective and safe for the host.

It has been well documented that traditional medicinal plants confer considerable antibacterial activity against various microorganisms (Jonathan et al., 2000). Many plants were reported to inhibit the growth of many oral bacteria (Pack et al., 1998), particularly Streptococcus mutans and control plague and thus prevent caries have been investigated (Jagtap and Karkera, 2000; Margan et al., 2001). Use of plant based alternatives for oral health has been successfully promoted for example, the use of antibacterial chewsticks has been widely advocated by health agencies where their use is culturally acceptable (Almas, 1999; Jagtap and Karkera, 2000). In the present study an attempt has been made to enrich the knowledge of antibacterial activity of ten Indian traditional medicinal plants that have been screened for antistreptococci activity.


Ethnobotany and Plant Collection
The ethnobotanical survey was conducted in Shevaroy and Kolli hills of Eastern Ghats of Tamil Nadu (Fig. 1), South India from January to July 2000. The comparison between medicinal and non-medicinal plants is based on research in the community namely Malayalis of the same areas.

Image for - Screening of Antibiotic Resistant Inhibitors from Indian Traditional Medicinal Plants Against Streptococcus mutans
Fig. 1:

Location map of Kolli and Shevaroy hills

Based on their information and literature we have collected 12 medicinal plants for antibacterial activity against Streptococcus mutans.

Extraction of Plant Materials
The collected plant materials were separated into leaf, root, bulb and bark and shade dried at 37°C for 7 days. The extracts were prepared using the solvents viz., water and ethanol. Dried plant materials (20 g) were extracted with 100 mL of water and ethanol for 72 h. Each mixture was stirred every 24 h using a sterile glass rod. At the end of fraction each extract was passed through Whatman No.1 filter paper. The filtrate obtained was concentrated in vacuo using rotary evaporator.

Test Bacteria
The test bacterium Streptococcus mutans was collected from Clinical Microbiology Laboratory, Sea Horse Hospital, Tiruchirappalli. Brain Heart Infusion (BHI, Difco) was used for the culture of Streptococcus mutans.

Antibacterial Assay
The disc diffusion assay of Iennette (1985) as described by Rosanaivo and Ratsimananga-Urverg (1993) and Rabe and Van Staden (1997) were used with modification to determine the growth rates ob bacterium with plants extracts. A diluted bacterial cultures (200 μL) was spread over Muller Hinton Agar Plates using sterile glass L-rod. Two hundred microliter of each extract was applied per filter paper disc (Whatman No.1, 6 mm diameter) and was allowed to dry before placing them on the agar plates in petriplates. Each extract was tasted in triplicate (3 discs/plate) and the plates were incubated at 37°C for 24 h and size of the growth zones were recorded. Calculations were carried out in triplicate with their mean values and standard deviation by using formula given by Gupta (1977).


The ethanolic bulb extract of Allium sativum was the most active against Streptococcus mutans. It showed high degree of inhibition (25.6 mm) followed by Azadirachta indica leaf extracts exhibited significant inhibition (24.4 mm) against the test bacterium. The ethanolic extracts of Embelia ribes fruit showed moderate inhibition (23.5 mm).

Table 1: Antibacterial activity of ten Indian Traditional medicinal plants
Image for - Screening of Antibiotic Resistant Inhibitors from Indian Traditional Medicinal Plants Against Streptococcus mutans

It was noted that the Streptococcus mutans was less susceptible to the extracts of Citrus medica roots (22 mm), Acacia nilotica barks (22.3 mm) and Calotropis gigantica leaves whereas the leaf residues of Ocimum sanctum and Tinospora cordifotia did not show any antibacterial effect on Streptococcus mutans. Complete absence of measurable inhibitory action was observed in the aqueous extracts of ten Indian Traditional medicinal plants (Table 1).

Among the plants tested Allium sativum was very promising and showed significant inhibition against the test bacterium. Numerous workers (Willis, 1956; Mantis et al., 1979; Jain, 1994) have obtained that garlic juice exhibits strong antibacterial properties and due to these properties garlic juice is very effective against various diseases. It is postulated that the antibacterial properties of garlic juice are due to the inhibition of succinic dehydrogenase via the inactivation of this groups (Srinivasan et al., 2001).


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