Oxidative stress is a condition when there is an excessive accumulation of reactive free radicals in cells, such as reactive oxygen species (ROS), reactive sulphur species (RSS), and reactive nitrogen species (RNS). Free radicals are all harmful compounds produced from various biological processes in the body such as breathing, digesting food, and drug metabolism  [1]. Free radicals are unstable due to the presence of unpaired electrons in their outermost electron orbit [2]. Because free radicals are very unstable and reactive, these compounds tend to neutralize themselves by reacting with other molecules that cause oxidation [3]. Therefore, antioxidant compounds are needed to prevent oxidative stress [4].

Antioxidants are compounds that can prevent or delay oxidation in a substrate at a lower concentration than the substrate. The use of synthetic antioxidants has several potential side effects such as causing strokes, nosebleeds, and skin rashes [5]. This has driven an increasing trend in society in the use of natural ingredients, so exploration is needed to study plants that contain antioxidant compounds. Phenolic compounds are often the focus of research in various studies on the antioxidant activity of medicinal plants. These compounds can be in the form of simple molecules such as gallic acid, caffeic acid, and hydrocortisone, or complex polyphenol compounds such as tannins and flavonoids. Polyphenols are known as very effective antioxidants because of their ability to neutralize free radicals through the donation of electrons or hydrogen atoms [6]. One of the flavonoids that has great potential as an antioxidant is anthocyanin [7].

Anthocyanins are blue, red, or purple pigment compounds that can be found in plant parts [8]. Anthocyanins are glycoside compounds of the flavonoid anthocyanidin which is its aglycone. Anthocyanins have several types such as cyanidin, delphinidin, pelargonidin, peonidin, malvidin, petunidin, and others, where all types are distinguished based on the hydroxylation position of the flavylium cation [9]. Based on its physical properties, anthocyanins are known as water-soluble pigments [10]. One of the plants that contains anthocyanins is basil leaves (Ocimum basilicum L.) [11]. Basil leaves (Ocimum basilicum) are plants from the Liliaceae family. This plant is spread in several regions such as India, Africa, South America, and the Mediterranean, where more than 150 species have been found [12,13]. Ocimum basilicum is a small annual plant with a rectangular upright stem and complete branches. Basil leaves are oval-lanceolate, pointed, toothed or entire, bald on both surfaces, arranged crosswise and light green in colour. The terminal leaf stalk is unbranched and the plant height ranges from 52.34 to 74.34 cm [14,15]. Based on several studies related to phytochemical screening of basil leaves, it is known that this plant contains alkaloids, terpenoids, tannins, flavonoids, saponins, glycosides, and ascorbic acid compounds. Identifying the relationships between several studies requires an analysis method called bibliometric analysis [16–18].

Bibliometric analysis is a methodological approach used to map and cartographically depict the body of scientific knowledge, utilizing unstructured data from various studies. This method can also serve as a parameter to evaluate research quality, explore key areas of research, and predict future research directions [19–21]. By quantitatively reviewing scientific publications, including keyword frequency, citation patterns, and networks between authors and institutions, bibliometric analysis can identify research trends [22]. This approach makes it easier for researchers to understand new trends, identify influential works, find research gaps, and simplify complex data using tools such as VOSviewer and RStudio, with comprehensive data sources such as PubMed [23,24]. Through this analysis, the development of trends and the current status of research related to the antioxidant activity of anthocyanins in basil leaves can be known. However, to date, there has been no study that specifically conducts a bibliometric analysis of anthocyanins in basil leaves as antioxidants. Therefore, this study aims to conduct a bibliometric analysis to visualize the relevance of related library data, so that it is expected to provide an in-depth understanding of the potential for new research ideas in exploring the antioxidant activity of anthocyanins in basil plants.

Article Search Strategy

The data in this study were taken from the PubMed database (https://pubmed.ncbi.nlm.nih.gov/) on August 2, 2024. The search was conducted using the keywords “Ocimum basilicum” AND “Flavonoid” to narrow the scope of articles relevant to the topic. The selected articles included original articles published in the last 10 years (2014-2024) and written in English. All data obtained were compiled and downloaded in PubMed format (txt).

Data Analysis

Bibliometric analysis of the obtained literature was performed using VOSviewer and RStudio software. VOSviewer (version 1.6.20), developed by the Centre for Science and Technology Studies at Leiden University, the Netherlands, was used to analyze keywords in the data based on their frequency of occurrence. Meanwhile, publication pattern analysis was performed using RStudio (version 2024.04.2+764) with the help of the Bibliometrix package. Bibliometrix is ​​software developed by the Department of Economics and Statistics of the University of Naples Federico II, Italy. Publication pattern analysis includes the number of publications per year, affiliated institutions, publishing scientific journals, and contributing authors.

Antioxidant

ROS are compounds that act as signal transduction molecules that drive cell activity and also provide cell protection when available in appropriate low amounts. RNS include free radicals nitric oxide (NO) and peroxynitrous acid (ONOOH) [25,26]. Nitric oxide synthase (NOS) catalyzes the oxidative transformation of L-arginine to NO, using NADPH as a cofactor. Abnormal excessive formation of NO through over-activation of NOS causes oxidative stress [27]. The reaction of NO with superoxide forms peroxynitrous acid. Peroxynitrous acid is involved in the nitration of protein tyrosine residues, thereby altering protein function [28]. This is the cause of the pathogenesis of oxidative stress-related diseases such as diabetes, obesity, and neurological diseases such as Alzheimer's and Parkinson's [29].

Antioxidants can be defined as compounds that can eliminate or inhibit the production of ROS [30,31]. Based on their origin, antioxidants can be categorized into exogenous and endogenous antioxidants [32]. Exogenous antioxidants are antioxidants obtained from outside the human body and can be compounds derived from natural products (fruits, vegetables, and meat) or synthetic products. Some compounds that can be obtained from natural products include vitamins, polyphenols, and carotenoids [33]. Endogenous antioxidants are antioxidants produced in the human body and are divided into two categories, namely enzymatic and non-enzymatic. Based on their mechanism of action, antioxidants can be classified into primary and secondary antioxidants [34]. Primary antioxidants are free radical scavenging agents that work by breaking the chain of free radical compounds. Meanwhile, secondary antioxidants can be divided into chelating agents, UV absorbents, singlet oxygen (O₂) reducers and oxygen scavengers [35]. One of the compounds that has the potential to have antioxidant activity is anthocyanin.

Anthocyanins are bioactive plant compounds that have various pharmacological effects, namely as antioxidants, anti-inflammatory, anticancer, and prevention of cardiovascular and neurodegenerative diseases [36]. The mechanism of action of anthocyanins as antioxidants is generally carried out by capturing free radicals (ROS and RNS). The flavylium framework gives anthocyanins a special feature involving the delocalization of radical electrons in the sp² orbital of the oxonium group [37]. The main role of the antioxidant activity of this compound is the oxidation of the phenolic hydroxyl groups of anthocyanins, especially the para- and ortho-phenolic groups which are important for the formation of semiquinones and for the stabilization of one-electron oxidation products [38].

Article Data Searches

The article search results are shown in Table 1, with a total of 111 articles meeting the inclusion criteria and used for bibliometric analysis. The search strategy used the Boolean operator "AND" to find articles containing both entered keywords. This approach aims to narrow the search results to focus on more specific topics related to the Ocimum basilicum plant and flavonoids. The search and sorting scheme for articles can be seen in Figure 1.

Table 1. Article Search Results using PubMed Search Engine

The obtained article data were analyzed using RStudio and VOSviewer software. RStudio offers the advantages of flexibility and customizability through script-based workflows and extensive libraries, such as Bibliometrix, that support complex analysis and integration with other data science tools. In addition, RStudio is open-source and supported by an active community, making it a strong choice for users with programming skills. On the other hand, VOSviewer is known for its user-friendliness due to its ability to analyze clusters and generate interactive maps, making it usable by researchers without the need for programming skills [39,40].

Figure 1. Flowchart of Article Data Search Procedure

 Annual Publication Trends

The trend of scientific publications in the period 2014–2024 is shown in Figure 2, with the peak number of publications occurring in 2022, where 18 articles were published. Overall, the annual trend analysis using Bibliometrix shows an increase in the number of publications by 8.2% over the past decade. These results indicate that research related to flavonoids, especially anthocyanins in basil leaves, remains relevant and continues to grow. This finding opens up opportunities to explore new research ideas in the development of antioxidant activity of anthocyanin compounds in basil leaves.

Figure 2. Trends in Development of Scientific Article Publications From 2014-2024

Visualization of Analysis of The Contributing Affiliation

The relevance of affiliations was analyzed based on the number of publications produced by institutions each year and the collaboration network between countries and institutions. From this analysis, 271 institutions were found to be affiliated with publications related to the activity of anthocyanins in Ocimum basilicum as antioxidants. The 20 institutions with the most publications are shown in Figure 3. Three institutions with the highest number of publications are Quaid-I-Azam University in Pakistan, University of Pisa in Italy, and King Saud University in Saudi Arabia. Several other institutions in the top 20 list have almost the same number of publications. Over the past decade, the largest increase in publications has occurred at Quaid-I-Azam University, which initially had no publications in 2014 and increased to 29 publications in 2021. However, since 2021, this institution has entered a stagnant phase with no new publications on the topic. The latest publication on the antioxidant activity of anthocyanins in Ocimum basilicum was found at King Faisal University, which has published six new articles in 2024. This trend shows that research on the topic of anthocyanin activity in Ocimum basilicum is still relevant to be developed.

Figure 3. Diagram of the Most Relevant Affiliation Based on the Number of Publications

The analysis continued by mapping the collaboration network between institutions. This mapping uses the Louvain algorithm, a hierarchical clustering algorithm that works by repeatedly combining communities into one node, then applying modularity clustering to the simplified graph. This algorithm measures the density of interconnected nodes in a random cluster [41]. The collaboration network between institutions is shown in Figure 4, showing five clusters distinguished by node colour. A total of 18 institutions were identified as being involved in the research collaboration. Collaborative relationships were only found within the same cluster, while there were no institutional connections between clusters.

Figure 4. Visualization of Inter-Institutional Collaboration Network

Visualization of Analysis of The Contributing Country

The visualization of the mapping of the countries involved can be seen in Figure 5a. These countries come from the continents of America, Europe, Africa, and Asia. One of the Asian countries that is also involved is Indonesia. Based on the map, the darker the intensity of the colour of the country marker, the greater the involvement of the country in this research topic. The results of the cross-country collaboration network analysis are shown in Figure 5b. This analysis identified seven clusters with different node colours, covering 41 countries involved in related research. The clusters were grouped based on the level of collaboration between countries in developing the topic of flavonoids from the Erythrina variegata plant. The strength of the relationship between countries was measured by the intensity of the connecting lines between nodes. Countries such as Italy, Pakistan, Iran, and Egypt stood out in each cluster, in line with the institutions with the highest number of publications based on the previous analysis. This collaboration network was also visualized through the country of origin of the corresponding author in Figure 5c. The results showed Italy as the country with the largest number of corresponding authors, producing 14 articles. The SCP index reflects collaboration within a country, while the MCP index shows collaboration between countries. This is in line with the results of the analysis which showed the University of Pisa in Italy as one of the universities with the highest number of publications.

Figure 5. Visualization of Analysis of The Contributing Country; (a) Country Collaboration Map; (b) Country Collaboration Network; (c) Corresponding Author’s Country

Visualization of Analysis of The Contributing Source

Figure 6 displays the top twenty most relevant journals based on the number of articles published in the last 10 years. The three journals with the highest number of publications on the topic of anthocyanin antioxidant activity in Ocimum basilicum are Plants (Basel, Switzerland) with 10 articles, Molecules (Basel, Switzerland) with 8 articles, and Food Chemistry with 6 articles. The numbers in the figure indicate the number of articles relevant to the topic being studied. The higher the number, the more related articles are published in the journal.

Figure 6. Diagram of the Most Relevant Source (Scientific Journals) Based on the Number of Publications

Visualization of Analysis of The Contributing Author

Analysis was conducted by considering the number of publications, research consistency, and relationships between the authors involved. Based on the visualization results, there are 604 authors listed in the search results literature. A total of twenty authors with the highest number of publications are shown in the diagram in Figure 7. The top four authors, namely Abbasi B.H., Guidi L., Hano C., and Landi M., each have 5 articles. Some articles and other details of the four authors with the highest number of publications are shown in the Table 2. Meanwhile, the other authors are involved in 1 to 4 articles.

Table 2. Details of the Four Authors with the Most Publications

Figure 7. Diagram of the Most Relevant Author Based on the Number of Publications

Research continuity is an important indicator to assess the development of the authors. The visualization in Figure 8 shows their research period. Of the four authors with the most articles, Guidi L. and Landi M. have the longest research period, which is 6 years (2014–2020). The author with the most recent research period is Gruda N.S., who was active from 2022 to 2024. This analysis indicates that the topic of anthocyanin compounds from the Ocimum basilicum plant remains relevant, supported by the continuity of research from old researchers as well as contributions from new researchers who are starting their publications.

Figure 8. Diagram of Author’s Production over Time

The collaboration network between authors was also analyzed and visualized in Figure 9 using the Louvain algorithm. This mapping identified 10 distinct clusters, with node colours indicating their clusters and 36 collaborating authors. Guidi L. and Abbasi B.H. were the most prominent authors in each cluster because their work was most frequently cited by other authors. Node size represents the level of collaboration, with larger nodes indicating greater influence. However, correlations between authors were only found within the same cluster, with no relationships between different clusters.

Figure 9. Visualization of Author’s Collaboration Network

Analysis of Keyword Co-Occurrence

Keyword occurrence analysis was conducted to identify the relationship between keywords that frequently appear in the collected articles, in order to generate new research ideas. Of the 729 keywords analyzed, the 20 keywords with the highest frequency of occurrence are summarized in Table 3. The keyword ‘Ocimum basilicum’ has the highest frequency of occurrence (occurrence 83; total link strength 263), indicating the high research interest in this topic. In addition, keywords such as ‘anthocyanins’ (occurrence 19; total link strength 79), ‘antioxidants’ (occurrence 41; total link strength 166), ‘humans’ (occurrence 11; total link strength 44), and ‘oxidative stress’ (occurrence 7; total link strength 32) are also included in the top list, indicating the relevance of research topic about antioxidant activity of anthocyanins from Ocimum basilicum plants against oxidative stress.

Table 3. Keywords with the Highest Frequency of Occurrence Analysis Results with VOSViewer.

The analysis continued with mapping the relationship between keywords using the full counting method, which allows all keywords in each article to be read by the VOSviewer system [42]. Based on the mapping visualized in Figure 10, there are 27 keyword clusters detected. Keywords such as Ocimum basilicum, anthocyanin, leaf extract, humans, and antioxidants are interrelated, confirming the relevance of research on the antioxidant activity of anthocyanin compounds from this plant in humans. This mapping also shows the frequency of keyword occurrence through differences in the size of the circles and text in the visualization. Keywords with a higher frequency of occurrence will be displayed with larger circles and text. This is in line with the data in Table 3, where the more frequently a keyword appears, the larger its size in the VOSviewer mapping.

Figure 10. Visualization of Keyword Mapping Based on Occurrence Using VOSViewer

Based on the results of bibliometric analysis, research on the antioxidant activity of anthocyanins in Ocimum basilicum plants remains relevant to be conducted. This conclusion is supported by the increasing research trend every year and the relevance of journals that publish related articles. The contribution of each author that continues to appear every year also indicates that there are still many researchers studying this topic. In addition, the strong relationship between the frequency of occurrence of the main keyword and other keywords further strengthens the relevance of this topic. Therefore, research on the antioxidant activity of anthocyanins in Ocimum basilicum has great potential to be developed with new, innovative ideas.

ACKNOWLEDGMENT

The author would like to thank the Pharmacy study program, Faculty of Mathematics and Natural Science, Udayana University for providing support and facilities in writing this article.

FUNDING STATEMENT

This research paper received no external funding.

CONFLICT OF INTEREST

The authors declare no conflicts of interest.

AUTHOR’S CONTRIBUTION

I Putu Dharma Raditya Wicaksana contributed to the concept development, data processing and visualization, and writing of the manuscript. I Dewa Made Siwananda contributed to the search and sorting of articles used as data in the research and literature search as a reference. Ni Made Widi Astuti also contributed to the concept development and supervision in the preparation of the manuscript.

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