Literature assessment and regional study characteristics
The data identification process through databases and screening of published documents was illustrated for this systematic review (Fig. 1). Overall, 5218 publications were identified from the search, and 1461 documents were excluded as duplicates. Finally, 3757 documents were screened and excluded (n = 1583), and only 2174 publications retrieved from 710 sources passed the rigorous inclusion criteria. The publication volume increased significantly (p = 1.7e - 10) after 39 years, culminating from the year 2000, and decreased in 2004. Eventually in 2006, there was a rapid increase of 51 published documents annually. The most published studies were recorded in 2018 and 2019 with 190 and 198 publications, respectively. The average annual percentage growth rate was 10.52% with a collaboration index of 2.88.
Of these 2174 publications (Table 1), 2072 were original articles with 95.31% more relative to other documents. Article in press was 1 (0.04%), book chapters were 6 with 0.27%, 2 (0.09%) for book reviews, 6 (0.27%) proceeding papers, 20 (0.92%) conference papers, 5 (0.23%) letters, 13 (0.60%) meeting abstracts, 21 (0.96%) reviews, 7 (0.32%) errata, 3 (0.14%) corrections, 1 (0.04%) data paper, 1 (0.04%) short survey, and 16 (0.73%) editorials documents.
A total of 138 medical plant species were the most reported for antimicrobial activity studies between the investigated timeline (Table 2). The studied species originated from 50 families, and Asteraceae (n = 17 species), Fabaceae (n = 16), Lamiaceae (n = 11), Moraceae (n = 16), and Myrtaceae (n = 11) were the top five plant families based on the number of investigated species. Nonetheless, 52 bacterial and 27 fungal species were the common microbes identified from the study (Table 3).
Scientific productivity of corresponding author’s countries
The information in Fig. 3 and Table 4 indicates the corresponding authors participation index of various countries. Within the Top 10, Egypt had the most corresponding author with 617 articles, followed by Nigeria (168), and South Africa. While Zimbabwe was the least country in article volume (11) of correspondence authors. The Single Country Publications (SCP) volume were ranged higher from Egypt (616) to Zimbabwe (11). However, South Africa had two Multiple Country Publications (MCP), Egypt and Ethiopia (1), while the rest countries had no MCP correspondence authors.
Most citation based on countries
The total number of citations received by individual countries within the selected study period are shown in Table 5. In descending order, Egypt had total of 13405 citations and 21.73 average citation per publication, followed by 3846 citations for South Africa and average of 25.47, Nigeria had 2667 total citations and 15.88 average, Morocco produced 2663 citations and average of 44.38, and Cameroon had 1673 cited articles with an average of 26.98 cited articles per year.
Most relevant journal sources
This study further showed the most relevant sources for the research work published on antimicrobial activities of medicinal plants between 1980 and 2019, as presented in Table 6. The top 10 represented journals are shown in descending order, were Journal of Heterocyclic Chemistry and Phosphorus, Sulphur and Silicon and related elements, with each generating 43 articles, followed by Journal of Ethnopharmacology with 42 articles, African Journal of Biotechnology with 40 articles, Molecules (35 articles) and South African Journal of Botany (35 articles), Fitoterapia (33 articles), Egyptian Journal of Chemistry (31 articles), Journal of Essential Oil Plants (27 articles), and Journal of Applied Pharmaceutical Science with 25 published articles.
Most productive authors
The information in Table 7 depicted the 10 most impactful authorship with this systematic review timeframe. The 1st most productive author was Kuete, V (31 articles) and affiliated with University of Dschang, Cameroon. The 2nd was van Vuuren, SF with 22 articles, University of Witwatersrand, South Africa. Afolayan, AJ as 3rd author with 21 articles, University of Forte Hare, South Africa. The 4th author was Viljoen, AM with 21 articles, Tshwane University of Technology, South Africa. The 5th was Abdel-Rahman, AAH (18 articles), affiliated with Assuit University, and Mansoura University both in Egypt. The 6th (Amr AEGE, 18 articles), 7th (El-Sayed WA, 18 articles), 8th authors (Al-Omar MA, 17 articles), and all the authors are affiliated with the National Research Center, Egypt. The 9th ranked author (Ngadjui BT, 16 articles), affiliated with University of Yaoundé, Cameroon. Finally, the 10th impactful author (Beng VP, 14 articles), affiliated with the University of Dschang, Cameroon.
Most cited scientific articles
The top 10 most cited article in the research area of antimicrobial activities of medicinal plants between 1980 and 2019 in Africa was shown in Table 8. Our results revealed that the most cited article was a review by 51, published by Journal of Pharmaceutical Analysis as an open access article was the most cited article with 1169 citations. Thus, this article reviewed various methods for evaluating antimicrobial analysis. The least cited article between our study period was a review article 52, published by Frontiers in Pharmacology as a toll access article, with a total citation of 145. The article revealed a considerable number of medicinal plant extracts and isolated compounds that possess significant antimicrobial effects on pathogenic microbes.
Word-cloud authors' collaboration networks and top keywords
The 20 word-cloud clusters in Fig. 4 showed the visualisation network of authors links related to antimicrobial activities of medicinal plants research within this systematic review period. The information in Fig. 4a revealed to 20 authors’ collaboration network. Moreover, Kuete V, had the major network followed by Ngadjui BT and Beng VP, respectively. The author Kuete V, collaborated with Ngadjui BT, Abegaz BM, Ngameni B, Beng VP, Meyer JM, Lall M, Bbaveng AT, and Etoa FX. Thus, having the strongest collaboration network with Ngadjui BT and Beng VP. On the contrary, Al-Omar MA collaborated with Ghabour HA, and Amr AE, while the authors El-Sayed WA, van Vuuren SF, and Tane P, collaborated with Abdel-Rahman AA, Viljoen AM and Kuiate JR, respectively.
Furthermore, Fig. 4b depicted the top 20 institutions’ collaboration network on antimicrobial activity of medicinal plants within the study period. The National Research Centre in Egypt had the major collaboration network, followed by Cairo University, and Suez Canal University. Cairo University had collaboration linked with the National Research Centre, Helwan University, Mansoura University, King Saud University, Suez Canal University and Tanta University. Cairo University had the strongest collaboration network, linked with the National Research Centre, while Alexandria University had the most collaboration network linked with the King Saud University.
Finally, Fig. 4c revealed the top 20 collaboration countries involved in antimicrobial activities of medicinal plants related research within the systemic review study. Countries such as Egypt, South Africa, and Nigeria, respectively produced the highest collaboration network strength. Egypt had most collaboration network linked with developed countries like the United States of America (USA), United Kingdom (UK), Italy, Germany, France, and China.
The information in Fig. 5 showed the summarised word occurrence frequency in a word-cloud for the top 50 most used title keywords in antimicrobial activities of medicinal plants research within the systematic review period. The prevalent words or terms used for this study were antimicrobial, antibacterial activity, antibacterial, antimicrobial activity, antifungal activity, essential oil, essential oil composition, medicinal plants, minimum inhibiting concentration. Other relevant words or frequently occurred were antibiotics, antimicrobial agents, characterisation, nanoparticles, phenolics, and phytochemical screening.