Bibliometric analysis of antibacterial activity of Centella asiatica : A study based on Scopus database

Centella asiatica (L.) Urb. has been recognized as a brain tonic. Other effects of C. asiatica have been widely investigated and reported, such as its antibacterial effect. However, there is no bibliometric study on this topic. Therefore, we performed bibliometric analysis to examine the papers related to the study of C. asiatica as an antibacterial agent. Bibliographic information of pertinent studies was collected from Scopus database. In this study, 89 papers published between 1997 and 2022 were selected. Bibliometric analysis was performed using Visualization of Similarities viewer (VOSviewer) version 1.6.18. Having been analyzed, it was found that Ubon Ratchathani University from Thailand was the most productive affiliation and the Journal of Ethnopharmacology was the most productive journal on the topic of antibacterial activity of C. asiatica . India was the most productive and the most collaborating country. According to the study of the most influential papers, author-based bibliographical coupling network, as well as keyword co-occurrence network and overlay, the variants of selected papers were from solvent extraction, bacteria-tested, plant components, and product formulations. We also found out that, following the formulation approach, both in vivo preclinical and clinical trials on this topic remain a potential study to be investigated to embrace phytomedicine as a therapeutic option.


INTRODUCTION
Nearly every place on Earth contains bacteria, including the human body.Bacteria are found on the skin, nose, mouth, throat, vagina, and gut.Some bacteria are pathogenetic.Numerous mechanisms are used by pathogenic bacteria to wreak harm on human hosts (Wilson, 2002).One of the immunological defenses against bacterial infection is formed by human skin.Numerous bacteria can come into contact with or settle on the skin (Aljamali et al., 2021).They typically wait until the skin is damaged before getting access to the underlying tissue (Sharma et al., 2021).The condition of infection and the ability of bacteria to replicate depend on whether the skin damage is classified as inflamed, colonized, localized/critically colonized, or invasively spread (Sharma et al., 2021).When bacterial skin infections do arise, they can affect any part of the body, either a small patch or the full surface.They may be mild or potentially fatal, depending on their severity (Ki and Rotstein, 2008).
to the antibacterial activity of C. asiatica in order to help other researchers in finding prospects for future study, prospects for collaboration with other institutions or authors, and impacted journals for publication of any study on this topic.

Data collection
Published papers about C. asiatica as an antibacterial agent were collected from Scopus database on November 10, 2022.Scopus database was chosen because it is a more thorough and larger database than the Web of Science, and it is beneficial both in keyword searching and citation analysis (Bamel et al., 2020;Effendi et al., 2021;Falagas et al., 2008).Google Scholar was not used since its poor data quality raises concerns about its usefulness for research evaluation (Mongeon and Paul-Hus, 2016).Data collection was performed by the following search: [TITLE-ABS-KEY ("Centella asiatica") Tracking literature for a pertinent topic has been challenging for researchers due to the recent rapid growth in the volume of research work.Therefore, bibliometric analysis methods were used to handle this vast amount of data (Zupic and Čater, 2015).A bibliometric study is usually used to assess the quality and quantity of published papers in order to identify trends in a given topic of study (Zuraidi et al., 2022).Large amounts of scientific data were investigated and analyzed by using bibliometric software, such as Visualization of Similarities viewer (VOSviewer), and scientific databases, such as Scopus (Donthu et al., 2021).A bibliometric study had been conducted using Derwent Data Analyzer to investigate papers on the subject of antibiotic-resistant bacteria that were obtained from the Web of Science between 2010 and 2020 (Sun et al., 2022).In the other studies, VOSviewer was used to determine the top 100 articles on the subject of antibiotics that were gathered from the Web of Science (Arshad et al., 2020).In this study, bibliometric analysis was conducted to explore papers related Bubbles are connected by lines that represent links.The distance between the two bubbles represents the relatedness of co-authorship, co-occurrence, and bibliographic coupling between the items (Romero and Portillo-Salido, 2019).The full counting method was used in this study.

Publication trends
Among 235 of the collected published papers related to the antibacterial activity of C. asiatica, only 89 papers met the inclusion criteria (Table 1).All selected papers included 72 journals and 376 authors.The oldest paper was published in 1997 by Fitoterapia entitled "Antibacterial activity of Centella asiatica" (Srivastava et al., 1997).The most recent paper was published in 2022 by the Research Journal of Pharmacognosy about the antimicrobial properties of C. asiatica and other plant extracts against Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and methicillin-resistant S. aureus (Tavakoli et al., 2022).
The number of publications on the topic of antibacterial activity of C. asiatica fluctuated over the years (Fig. 2).Between 1998Between and 2002Between , and in 2013, there was no published paper on this topic.In 2020, scientists were expected AND TITLE-ABS-KEY (antibacteria*) OR TITLE-ABS-KEY (antimicrobia*)].The double quotation marks indicate a loose or approximate phrase.The asterisk or star-shaped symbol stands for any combination of characters in Scopus data syntax (Ha et al., 2020).The search was limited to title, abstract, and keywords.The range of years was not determined.

Data screening, extraction, and analysis
Only published papers that met the inclusion criteria would be analyzed.Original articles, conference papers, writing in English, and a study of the antibacterial activity of C. asiatica were among the inclusion criteria.Figure 1 provides a summary of the record-gathering and study-elimination procedure.For further analysis, the selected papers were extracted into CRV format (file.crv)and exported to VOSviewer version 1.6.18as a bibliometric tool (Ha et al., 2020).Countries' co-authorship, keywords' co-occurrence, and authors' bibliographic coupling were presented as network visualization maps.The items (countries, keywords, and authors) were visualized as a bubble.The size of the bubble is reflected by the weight of each item (van Eck and Waltman, 2022;Yeung et al., 2020), which is proportional (Romero and Portillo-Salido, 2019).The color of the bubble describes the cluster where the item belongs.Indonesia and Thailand with 10 papers.Thailand came with the highest average number of citations (AC) among the most productive countries, followed by the United Kingdom.The collaborations of countries were visualized using co-authorship analysis with countries as the unit of analysis on VOSviewer.The minimum number of papers and the minimum number of citations for a country were set at 1 and 0, respectively.The network visualization result of collaboration between countries that contributed to the research study on the antibacterial activity of C. asiatica is shown in Figure 3.Among 27 countries, the largest connected countries only consisted of nine: India, Saudi Arabia, South Korea, Australia, Thailand, Malaysia, Ethiopia, Bahrain, and Turkey.India had the greatest number of links, which was 6.Therefore, India came out as the country with the biggest collaboration.It collaborated with Saudi Arabia, South Korea, Malaysia, Ethiopia, Bahrain, and Turkey.

Contribution by affiliations
Based on the 89 selected papers, 160 affiliations provided a research study on the antibacterial activity of C. asiatica.Table 3 shows the most productive affiliations, with at least two papers published on the topic.The most productive affiliation was Ubon Ratchathani University, with three papers.Among the 16 affiliations on the list, India had 7 affiliations, Malaysia had 6 affiliations, Thailand had 2 affiliations, and South Korea had 1 affiliation.All of the countries with the most productive affiliations are on the Asian continent.The highest AC among the most productive affiliations was Universiti Sains Malaysia, with 57.50.It indicates that the papers produced by Universiti Sains Malaysia on this topic are more influential than those from Ubon Ratchathani University.

Contribution by journals
The 89 selected research papers on the antibacterial activity of C. asiatica were published in 72 journals.Ten of them published more than one paper.The top four journals with the most papers published on the topic are presented in Table 4.The most productive journal on this topic was the Journal of Ethnopharmacology from Elsevier Ireland Ltd. with 6 papers and AC 102.33 (the latest paper on the topic of the antibacterial activity of C. asiatica was published in 2022), followed by the International Journal of Phytomedicine, the Journal of Pure and Applied Microbiology, and the Pharmacognosy Journal, which published three papers.The African Journal of Biotechnology, the Asian Pacific Journal of Tropical Biomedicine, the Biomedical and Pharmacology Journal, the Journal of Food Processing and Preservation, Polymers, and In Chemistry Communications published two papers on the topic.This information will assist the scientists in seeking out a specific journal and submitting their reports of study on this topic to those journals (Arifah et al., 2021).The Journal of Ethnopharmacology can be considered a targeted journal for the publication of articles on the antibacterial activity of C. asiatica.

Analysis of authors and their bibliographical coupling network
Of the 89 selected papers, 376 authors contributed to the studies of the antibacterial activity of C. asiatica.Only 13 to become more interested in this topic based on the increasing number of papers.The largest number of publications occurred in 2021 with 12 papers.

Contribution by countries and their collaborations
Twenty-seven countries performed a research study on the antibacterial activity of C. asiatica in 89 papers that were selected for this study.The number of papers by the most productive country in the field of the topic is presented in Table 2.The countries in the Asia continent dominated the list.The most productive country was India with 36 papers.It means India has made a noteworthy contribution to this topic compared to the rest of the countries.The second-most productive country was Malaysia with 15 papers, followed by   authors published more than 1 paper; the highest number of papers per author was 2. It indicated the number of researchers who focused on this topic was low.
The most productive authors are presented in Table 5.They were affiliated with colleges in India (6), Thailand (3), Indonesia (2), and Malaysia (2).This is connected to the Southeast Asian region, where C. asiatica originated (Chandrika and Prasad Kumara, 2015;Orhan, 2012).By knowing the author's name, affiliation, and country of origin, other researchers interested in this topic can create and promote research collaboration (Arifah et al., 2021).
A bibliographical coupling of authors was performed to analyze the authors who published two papers that cited the coupling strength (Ma et al., 2022).A higher coupling strength indicates more shared citations between the two papers (Ma et al., 2022).The minimum number of papers for an author was set to 2. Thirteen authors met the criterion, but the largest set of linked authors consisted of only 8 authors.
The outcome of the network visualization of bibliographical coupling based on the authors' studies is shown in Figure 4. Three clusters were obtained.The clusters indicated that there was a relationship between the authors (Effendi et al., 2021).Clusters 1, 2, and 3 were represented with red, green, and blue nodes, respectively.Cluster 1 consisted of Diky Setya Diningrat, Martina Restuati, and Varahalarao Rao Vadlapudi.Cluster 2 consisted of Parichat Phumkhachorn, Pongsak Rattanachaikunsopon, and Patchanee Yasurin.Cluster 3 consisted of Suzita Ramli and Junxian Wong.Due to the fact that each author had two papers, the bubble sizes are all the same.
There were 17 links among the authors.Each link has a strength representing the number of cited references that the two papers share (van Eck and Waltman, 2022).Patchanee Yasurin has the greatest number of links, which are linked to Parichat Phumkhachorn, Pongsak Rattanachaikunsopon, Diky Setya Diningrat, Martina Restuati, Suzita Ramli, and Junxian Wong.It indicated that Patchanee Yasurin's papers and those authors' shared some cited references in common.His first paper investigated the impact of C. asiatica's solvent extraction on its chemical composition and antibacterial activity against various microbial pathogens (Rattanakom and Yasurin, 2015).It was similar to his linked authors' papers.The variants came from testing microorganisms, plant components, and solvent extractions (the brief of the study is presented in Table 5).Meanwhile, his second paper investigated the antibacterial   activity of gelatin nanoparticles loaded with C. asiatica chloroform extract (Kesornbuakao et al., 2018).

Analysis of cited papers
The more the paper is cited, the higher its influence is on this topic.Among the 89 selected papers, 37 had been cited at least 10 times, and 5 had been cited at least 100 times.Table 6 shows the five most frequently cited papers, which have been cited more than 100 times.Logeswari's team paper had the highest citation, having been cited 363 times.Their paper was published in the Journal of the Saudi Chemical Society in 2015 with the title "Synthesis of silver nanoparticles using plant extract and analysis of their antimicrobial properties."They used the extracts of C. asiatica, Ocimum tenuiflorum, Solanum trilobatum, Syzygium cumini, and Citrus sinensis to synthesize silver nanoparticles and evaluated the antibacterial activity of the synthesized silver nanoparticles using the well diffusion method.Other top five cited papers were published earlier (before 2010), most of which were published in the Journal of Ethnopharmacology.It is in accordance with the results of the most productive journals.

Keyword co-occurrence network
The co-occurrence analysis of keywords was conducted to determine which one frequently occurred.It will help researchers spot the most popular topics and emerging trends in a field.In a paper, two words that cooccur quite often may have a stronger connection than other word pairs (Romero and Portillo-Salido, 2019).The author keyword was chosen as the unit of analysis.Of the 89 selected papers, there were 286 keywords provided by the authors.The minimum number of occurrences of a keyword was set at 2. Thirty-four keywords met the threshold, but only 32 keywords made up the largest set of linked keywords.
Figure 5 shows the mapping of the co-occurrence analysis of these 32 connected keywords."Centella asiatica" had the most links, with 21 links.The co-occurrence strength between two keywords is represented by the thickness of the link line and it is directly proportional (Feng and Chen, 2020)."Centella asiatica" had a thicker link with both "antibacterial" and "antimicrobial activity" than the other keywords that connected to "Centella asiatica."It related to the searches performed on the data collection.The keyword "Centella asiatica" was also connected to "wound healing", "antioxidant activity", "antifungal", and "antibiofilm", which indicated other pharmacological activities of C. asiatica.It had also been investigated in several studies.The top seven keywords in selected papers on the topic of the antibacterial activity of C. asiatica were "Centella asiatica," "antibacterial activity," "antimicrobial activity," "medicinal plants," "antibacterial," "antimicrobial," and "antioxidant" (Table 7).In the early years, the terms such as "antimicrobial activity," "apiaceae," "disc diffusion," and "plant extract" tended to appear frequently in author keywords.In contrast, "Staphylococcus aureus," "wound healing," "chitosan," "cyclic voltammetry," and "photocatalysis" appeared in recent years, indicating that they have been the current research hotspots.
The term "chitosan" was used in two papers that investigated the use of chitosan and C. asiatica in bilayer patches against Propionibacterium acnes (Kuo et al., 2021) and in hydrogel as a wound dressing (Wang et al., 2021).This showed that the recent research topic of the antibacterial activity of C. asiatica has included the formulation strategy.In view of the antibacterial activity of C. asiatica already explored in several solvent extractions (aqueous, ethanol, methanol, and chloroform) and bacteria (Nasution et al., 2018), the formulation strategy remains promising to be explored and followed by in vivo preclinical and clinical trials of the developed products.For example, the in vivo preclinical or clinical trial of developed products of wound  dressing containing C. asiatica extract (either using aqueous, ethanol, methanol, chloroform, or other solvent extractions) for diabetes wounds or burns can be explored.

CONCLUSION
This study found a fluctuating number of papers related to the topic between 1997 and 2022.General information about the papers was also provided, including the most productive country (India), the most collaborating country (India), the most productive affiliation (Ubon Ratchathani University), the most productive journal (Journal of Ethnopharmacology), the most cited paper (Synthesis of silver nanoparticles using plant extract and analysis of their antimicrobial properties by Logeswari et al. [2015]), and the most frequent keyword ("Centella asiatica").Furthermore, information from the keyword co-occurrence network revealed that the formulation approach has been studied recently concerning the antibacterial activity of C. asiatica.
The formulation strategy of C. asiatica as an antibacterial agent, followed by its in vivo preclinical and clinical trials, remains a promising study to be explored in order to adopt phytomedicine as a therapeutic option.

Figure 2 .
Figure 2. Publication trends on the topic of antibacterial activity of C. asiatica.

Figure 3 .
Figure 3.The network visualization of co-authorship analysis of countries on the topic of antibacterial activity of C. asiatica.

Figure 4 .
Figure 4.The network visualization of bibliographic coupling of authors on the topic of antibacterial activity of C. asiatica.

Figure 5 .
Figure 5.The largest set of connected author keywords on the topic of antibacterial activity of C. asiatica.(a) The mapping of VOSviewer network visualization.(b) The mapping of VOSviewer overlay visualization.

Table 1 .
Selected papers from early to recent years.In vitro antibacterial and cytotoxic activity of leaf extracts of Centella asiatica (L.) Urb, Warburgia salutaris (Bertol.F.) Chiov and Curtisia dentata (Burm.F.) C.A.Sm-medicinal plants used in South Africa In-vitro study of the effect of Centella asiatica on cholera toxin production and the gene expression level of ctxA gene in Vibrio cholerae isolates Journal of Ethnopharmacology Wong et al. (2021) Assessment of toxic effect of Centella asiatica extract and its application as natural preservative in fresh-cut mango, pear and cabbage Journal of Food Processing and Preservation Use of Cassia alata aqueous extract as a bath treatment to control Pseudomonas anguilliseptica infection in tilapia (Oreochromis niloticus) Archives of Biological Sciences Valle et al. (2015) Antibacterial activities of ethanol extracts of Philippine medicinal plants against multidrug-resistant bacteria Asian Pacific Journal of Tropical Biomedicine Panda et al. (2016) Large scale screening of ethnomedicinal plants for identification of potential antibacterial compounds Molecules BMC Complementary and Alternative Medicine Kesornbuakao et al. (2018) The antibacterial and antioxidant activity of Centella asiatica chloroform extract-loaded gelatin nanoparticles MATEC Web of Conferences Jantarat et al. (2018) In vitro antimicrobial activity of gel containing the herbal ball extract against Propionibacterium acnes Scientia Pharmaceutica Nasution et al. (2018) Antimicrobial activities of Centella asiatica leaf and root extracts on selected pathogenic micro-organisms Journal of Medical Sciences (Faisalabad) Rekha et al. (2018) Antibacterial efficacy and minimum inhibitory concentrations of medicinal plants against wound pathogens Biomedical and Pharmacology Journal Restuati and Diningrat (2018) Antimicrobial profile of Premna pubescens.Blume and Centella asiatica extracts against bacteria and fungi pathogens International Journal of Pharmacology Rebia et al. (2019) Natural antibacterial reagents (Centella, propolis, and hinokitiol) loaded into poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] composite nanofibers for biomedical applications Nanomaterials Sardrood et al. (2019) Chemical Composition and Biological Activity of Essential Oils of Centella asiatica (L.) Toxicology and Environmental Health Sciences Kanchan et al. (2019) Virulence of Aeromonas hydrophila in Siamese fighting fish (Betta splendens) and the bacterium susceptibility to some herbal plants Iranian Journal of Fisheries Sciences Rukisah et al. (2019) In vitro antibacterial efficacy of leaves extract of Centela asiatica against Vibrio harveyi and Aeromonas hydrophila Indonesian Aquaculture Journal Sari et al. (2019) The application of multiplate resazurin reduction assay in the screening for anti-mycobacterial activity from Indonesian medicinal plants Indonesian Journal of Pharmacy Selvam et al. (2019) Effects of extraction methods on antibacterial activity of Centella asiatica leaves against pathogenic Staphylococcus aureus and Escherichia coli Wahdany et al. (2020) Antibacterial activity of asiaticoside towards Enterrococcus faecalis in periapical infections Biochemical and Cellular Archives Pham et al. (2020) Green synthesis and antibacterial activity of HAp@Ag nanocomposite using Centella asiatica (L.) urban extract and eggshell International Journal of Biomaterials Antimicrobial activity of Centella asiatica and Gigantochloa apus Journal of Basic and Clinical Physiology and Pharmacology Swastini et al. (2021) Cold cream combination of Garcinia mangostana L. Anredera cordifolia (ten.) and Centella asiatica extracts on burn healing activity test Mehta et al. (2022) Role of medicinal plants from North Western Himalayas as an efflux pump inhibitor against MDR AcrAB-TolC Salmonella enterica serovar typhimurium: In vitro and in silico studies Journal of Ethnopharmacology Khan et al. (2022) Anti-quorum sensing, antibiofilm, and antibacterial activities of extracts of Centella asiatica L. leaves, and in vitro derived leaves-calli through tissue culture: a potential for biofouling-prevention Biofouling

Table 2 .
The most productive countries on the topic of antibacterial activity of C. asiatica.

. Country Number of papers Citations AC a per paper
a AC: average number of citations.

Table 3 .
The most productive affiliations on the topic of antibacterial activity of C. asiatica.
a AC: average number of citations.

Table 4 .
The most productive journals on the topic of antibacterial activity of C. asiatica.

Table 5 .
The most productive authors on the topic of antibacterial activity of C. asiatica.
a AC: average number of citations.

Table 6 .
Top five cited papers on the topic of antibacterial activity of C. asiatica.

Table 7 .
Top seven keywords with the highest frequency of occurrence.