Biomedical and Biotechnology Research Journal (BBRJ)

: 2021  |  Volume : 5  |  Issue : 1  |  Page : 1--6

Antimicrobial traits of different medicinal plants locally available in Bangladesh

Farzana Hossaini1, Nayan Chandra Das2, Fahamida Hossaini3, Mrityunjoy Acharjee4, Saurab Kishore Munshi2,  
1 Department of Microbiology, Stamford University Bangladesh; Nutrition and Clinical Services Division, Emerging infections and Parasitology Laboratory, International Centre for Diarrheal Disease Research, Dhaka, Bangladesh
2 Department of Microbiology, Stamford University Bangladesh, Dhaka, Bangladesh
3 Department of Pharmacy, State University of Bangladesh, Dhaka, Bangladesh
4 Department of Microbiology, Stamford University Bangladesh, Dhaka, Bangladesh; Department of Bioscience, Graduate School of Science and Technology, Shizuoka University, Oya, Suruga-Ku, Shizuoka, Japan

Correspondence Address:
Mr. Saurab Kishore Munshi
Department of Microbiology, Stamford University Bangladesh, 51. Siddeswari Road, Dhaka 1217


Background: Medicinal plants have been commonly used in traditional medicine against different ailment from ancient time. The present study was an attempt to determine the anti-bacterial traits of commonly available medicinal plants, especially having topical uses. Methods: A total of four types of locally available medicinal plant samples inclusive of Turmeric (Curcuma longa, rhizome), Marigold (Tagetes minuta, leaves), Durva Grass (Cynodon dactylon, whole plant), and Hibiscus (Hibiscus rosa-sinensis, leaves) were collected. Crude, hot water, and solvent (ethanolic and methanolic extracts of the samples) were tested for their antimicrobial traits by agar well-diffusion method on Mueller-Hinton agar. The minimal inhibitory concentration (MIC) of each sample was determined by the microdilution technique. Microbiological quality of the samples was also checked. Results: Microbial contaminations were found in all the samples. Beside viable bacteria and fungi, all samples contained Staphylococcus spp. and Pseudomonas spp. The proliferation of Klebsiella spp. was observed in the majority of the samples. Notable antimicrobial activities were exhibited by the medicinal plant parts tested in this study. Ethanolic and methanolic extracts showed remarkable efficiency in eliminating the growth of tested bacterial isolates although crude and hot water extracts projected no considerable inhibitory effects. The majority of the samples had a MIC value at 12 mg/mL. Conclusion: The findings of the present study reveal that the medicinal plant samples had remarkable antimicrobial traits which portray their potential for the commercial application against different infectious diseases.

How to cite this article:
Hossaini F, Das NC, Hossaini F, Acharjee M, Munshi SK. Antimicrobial traits of different medicinal plants locally available in Bangladesh.Biomed Biotechnol Res J 2021;5:1-6

How to cite this URL:
Hossaini F, Das NC, Hossaini F, Acharjee M, Munshi SK. Antimicrobial traits of different medicinal plants locally available in Bangladesh. Biomed Biotechnol Res J [serial online] 2021 [cited 2022 Nov 28 ];5:1-6
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The employment of medicinal plants as folk medicines to prevent and cure several ailments may vary among different communities.[1],[2],[3] Before the start of the use of synthetic drugs, medicine had depended exclusively on leaves, flowers, and barks of plants. Medicinal plants and/or their derivatives are still dominating in the preparation of homeopathic and ayurvedic medicines. However, at present <50% of the modern pharmacological drugs are based on chemicals identified in plants.[2] In recent years, infectious diseases are considered to be major concerns worldwide, especially due to the emergence of drug resistance among human pathogenic bacteria and fungi.[4],[5] Moreover, toxicity issues related to synthetic drugs aid in limiting the use of antimicrobial agents.[6] Such factors urge the needs to explore other suitable options as a source of antimicrobial agents.[5],[7]

Many of the modern pharmaceuticals are largely based on plants and plant-based medicaments against various ailments. The interest in investigations on the potential of medicinal plants as natural products is rising day-by-day in different parts of the world.[8] Such plants contain active chemical compounds with high antioxidant properties that aid in various disease preventions.[9] With more extensive studies for natural therapies, plants have been a valuable source of natural products for preserving human health for a long period, particularly in the last decade.[8] Currently, the use of phytochemicals such as vitamins (A, C, E, and K), carotenoids, terpenoids, flavonoids, polyphenols, alkaloids, tannins, saponins, pigments, enzymes, and minerals has gradually increased for medicinal purposes in many countries.[10],[11] Medicinal plants would be the best source to obtain a range of drugs according to the World Health Organization (WHO). About 80% of people from developed countries use traditional medicine, which has medicinal plant-derived compounds.[8],[12]

It is clear that an inexhaustible source of active ingredients, invaluable in the management of many intractable diseases, is present in the plant kingdom.[12],[13] In all plant cells, bioactive compounds are typically accumulated as secondary metabolites, but their concentration varies according to the plant components, seasonal environment and specific growth phase. Leaf is one of the largest accumulated plant components of such compounds and is commonly chosen for therapeutic purposes by individuals, for which some of the active compounds inhibit the growth of pathogenic microbes either alone or in combination. The biochemical, antimicrobial, and hypoglycemic activities of medicinal plants have been tested worldwide.[12],[13],[14] Antiulcerogenic, antihelminthic, hepatoprotective, analgesic, antipyretic, anti-leishmanic, and insecticidal activities have also been investigated by several researchers.[8],[9],[10],[11],[12],[13],[14] Because of their contributions to health care, scientific studies of medicinal plants have been undertaken in many counties. The key advantages of the use of plant-based medicines are their safety and affordability compared to synthetic alternatives.[15]

Considering all these fact, we designed the study to investigate the antimicrobial traits of some medicinal plants, currently used by Bangladeshi people to treat their illness. Plants were collected from different areas of the country and tested for the presence of antibacterial activity through agar well-diffusion method following ethanol, methanol and hot water extraction, and by measuring minimal inhibitory concentration (MIC) using microdilution technique.


Study area, sampling, and sample processing

A total of 20 samples of four varieties (five samples of each variety) of medicinal plant, those have topical applications, including Turmeric (Curcuma longa, rhizomes), Marigold (Tagetes minuta, leaves), Durva Grass (Cynodon dactylon, whole plant), and Hibiscus (Hibiscus rosa-sinensis, leaves) were collected from different locations of Dhaka, Bangladesh, from November 2019 to February 2020. Both samples were processed aseptically, accompanied by homogenization of 10 g of each sample with 90 mL of normal saline and serially diluted up to 10−4 to conduct microbiological assay.[16],[17],[18],[19]

Estimation of microbial contaminants of the samples

An aliquot of 0.1 mL of each sample suspension was inoculated from dilutions 10−2 to 10−4 to the Nutrient agar (NA) and Sabouraud's dextrose agar (SDA) plates for the enumeration of total viable bacteria and fungi, respectively through the spread plate technique. To determine the level of contamination by coliforms (especially, Escherichia coli, and Klebsiella spp.), fecal coliform, Staphylococcus spp. and Pseudomonas spp., 0.1 mL of each sample from dilutions 10−2 to 10−3 was spread out consecutively onto MacConkey (MAC) agar, Membrane Fecal Coliform (mFC) agar, Mannitol Salt Agar, and Pseudomonas agar (PA) plates. NA, MAC, MSA, and PA Plates were incubated for 24 h at 37°C whereas, SDA plates were incubated at 25°C for 48 h for the appearance of visible colonies. The incubation of mFC agar plates was carried out at 44.5°C for 24 h.[17],[18],[19],[20]

Solvent extraction and conduction of antimicrobial assay

The powdered form of each sample (dried) was prepared by grinding and 15 g of powder was applied to 85 mL of ethanol and methanol in a Durham's bottle for the preparation of methanolic and ethanolic extracts. The bottles were then held for 24 h at 130 rpm in a shaking water bath at 24 ° C. Following filtration of the extract solutions, the pellets of the samples were then collected.[17],[18],[19]

Agar well-diffusion method was employed[17],[18],[19] to determine the anti-bacterial properties of crude, hot water, and solvent extracts of the medicinal plant samples against different previously isolated bacterial strains of the laboratory such as E. coli, Pseudomonas spp., Vibrio spp., Klebsiella spp., Staphylococcus spp., Listeria spp., Salmonella spp., and Bacillus spp. Initially, the lawn was prepared from each bacterial suspension (105 cfu/mL or 0.5 OD determined by spectrophotometer) on Mueller-Hinton agar, and 100 μl (at a residual sample concentration of ~11.1 mg/mL) of each crude, hot water, ethanol, and methanol extract was dispensed into the wells generated on MHA.[17],[18],[19] As negative controls, buffer peptone water, absolute ethanol and methanol were used whereas gentamicin antibiotic discs (10 μg) were used as a positive control.[19] The plates were incubated for 12 h–18 h at 37°C and examined for the zone of inhibition (mm) formation.

Determination of the minimal inhibitory concentration through broth microdilution method

Microdilution method was applied for the assessment of the MIC of the medicinal plant samples.[16],[19] A total of 100 μL of the overnight (~12 h) culture of each of the previously mentioned bacterial isolates was inoculated into the correctly labeled sterile tubes containing MH broth (turbidity adjusted to 0.5 McFarland standard). At residual concentrations of 0.4, 0.8, 1.5, 3, 6, 12, and 24 mg/mL, medicinal plant samples were further added into the suspension and the tubes were incubated for 24 h at 37°C. The lowest concentration (mg/mL) of each sample that could visibly inhibit the multiplication of the bacteria tested was determined as the MIC value.[16],[19]

 Results and Discussion

Recovery of microorganisms from medicinal plant samples

For medicinal plants to be applied as therapeutic agents, it is necessary to ensure the safety of the consumers as diseases may result from contaminant microorganisms and their toxins, rendering them harmful for consumption.[21],[22] Bacterial and fungal contamination can occur as a result of improper handling during harvesting, processing, manufacturing, distribution, or storage of the medicinal plant samples.[16],[23],[24] When checking for the efficacy of medicinal plants, it is therefore also necessary to determine the presence of microbial contaminants.[21] Microbial contaminations in the medicinal plants were evident in the current investigation. The tested samples contained viable bacteria in a range of 4.8 × 105 cfu/g to 5.2 × 107 cfu/g, whereas fungi were encountered in an average of 104 cfu/g [Table 1]. For medicinal plants which are intended for oral consumption, the colony counts of microbial contaminants should not exceed 105 cfu/g according to the WHO.[24] However, the colony count should not exceed 107 cfu/g for microbial contaminants for plant products which are applied for topical use or those that are pretreated with boiling water. As the medicinal plants tested in this study are mostly used topically, the contamination with viable bacteria was within acceptable limits.{Table 1}

Addressable numbers of specific bacterial species were also isolated from the tested medicinal plant samples [Table 1]. Among all the isolates, Staphylococcus spp. and Pseudomonas spp. were predominant which was found in all the samples with an average count of 104 cfu/g. Except for turmeric rhizomes ones, Klebsiella spp. were present in all the other samples. Only Marigold leaf samples contained E. coli proliferation. The tested medicinal plants were devoid of fecal coliform contamination [Table 1]. Similarly, several studies previously found significant contaminations by specific bacterial and fungal species in medicinal plants and herbal medicines all over the world.[16],[18],[19],[21],[22],[23] The presence of specific bacterial isolates which might inclusive of pathogenic strains in the medicinal plants samples could cause harm to the consumers. Appropriate regulation could mitigate against factors that have negative consequences for human health and safety. As microbial contamination is a common phenomenon in natural products, proper regulations, and implementing good manufacturing and processing practices could ensure the safety and quality of the medicinal plant products.

Antimicrobial potential of the medicinal plant samples

Plant extracts comprises of unique antimicrobial compounds which have immense potential against bacterial pathogens.[8] A number of reports showed the antibacterial properties of medicinal plants suggesting them as a good alternative for synthetic drugs.[5],[8],[12],[25],[26],[27] In the present study, all the medicinal plant samples exhibited to contain noticeable broad spectrum of antimicrobial activities against tested microorganisms in agreement with the previous studies [Table 2],[Table 3],[Table 4],[Table 5], [Figure 1]. Hot water extracts of the samples merely have any impact on inhibiting the growth of tested bacterial isolates [Table 2],[Table 3],[Table 4],[Table 5]. Crude extracts of turmeric rhizomes and marigold leaf samples showed antibacterial activities to some extent, while of Durva Grass, and Hibiscus leaf samples almost did not affect the bacterial isolates. However, the scenario was drastically different in the case of solvents extracts. The ethanolic and methanolic extracts of Durva Grass samples were successful in eliminating all the tested bacteria with a significant zone of inhibition [Table 4]. Satisfactory results were also documented for the solvent extracts of turmeric rhizomes, marigold leaf, and Hibiscus leaf samples having inhibitory effects against the majority of the bacterial isolates tested [Tables 2, 3 and 5]. Though marginally, ethanolic extracts of the medicinal plant samples were found to be superior in inhibiting pathogens than the methanolic extracts. However, Selvamohan et al.,[12] Dabur et al.[25] and Males et al.[28] found methanolic extract of medicinal plants to be more effective than the ethanolic and aqueous extracts in their study against different bacteria.{Figure 1}{Table 2}{Table 3}{Table 4}{Table 5}

The lowest MIC value of the medicinal plant samples was recorded to be 6 mg/mL which found against some tested bacteria, while the highest MIC value was 24 mg/mL [Figure 1]. Majority of tested bacterial isolates were found to be inhibited at a sample concentration of 12 mg/mL. In terms of MIC, marigold leaf samples showed better proficiency in eliminating pathogens [Figure 1]. Obeidat[5] found MIC value at 16 and 32 mg/mL with 4 mg/mL as the lowest value in the medicinal plant samples they tested.


The presence of viable bacteria and fungi as well as the specific bacterial isolates in the tested samples, though bacterial counts did not exceed the marginal limits, is advocating for the implementation of proper aseptic condition during manufacturing and processing of the herbal medicines from plant sources. Overall, the medicinal plant samples especially their ethanolic and methanolic extracts displayed strong antibacterial activity, as shown by the agar well diffusion method and MIC assay. Hence, the presence of anti-bacterial traits in the samples meant that the medicinal plants tested could be effective against many of the disease complications. These findings allow us to recommend the widespread use of herbs and herbal medicines by registered practitioners for the treatment of infectious diseases.


Authors would like to thank Stamford University Bangladesh for providing all the necessary facilities to carry out the research.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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