Plant Phyto-constituents as Antibiotic Adjuvants: A Systematic Review and Bibliometric Analysis

The advent of antibiotics in the 19th century has significantly reduced the morbidity and mortality of infectious diseases. However, irrational use of antibiotics in humans as well as in animals has driven the 21st century to the rapid emergence of MultiDrug Resistance Bacteria (MRB). Moreover, the dissemination of COVID-19 pandemic has paved the way for MRB, typically due to increased use of antibiotics to avoid secondary infections. The fast pace progression of bacterial resistance for the antibiotics and their combinations is making the management of MRB infections tough and increasing the cost of the treatment as well. However, use of Efflux Pump Inhibitors (EPI) as adjuvant for antibiotics has shown a ray of hope by retaining the susceptibility of the antibiotics and thereby reducing the burden of immediate requirement of new antibiotics for MRB. Accordingly, the present paper is aimed to scrutinize the predominant literature depicting the plant Phyto-constituents as an EPI and adjuvant for antibiotics in the management of MRB infections. Review Article Dongre et al.; JPRI, 33(41B): 335-351, 2021; Article no.JPRI.71713 336 The systematic review of the present paper indicates that the plant phyto-constituents belonging to the class of alkaloids, terpenoids, flavonoids can effectively be used as EPIs for antibiotics such as Ciprofloxacin, Norfloxacin, Tetracyclines and Chloramphenicol. Bibliometric analysis indicates that the Journal of Antimicrobial Chemotherapy, Antimicrobial Agents and Chemotherapy and BMC Complementary & Alternative Medicine have published impactful articles on EPI potential of plant phyto-constituents. Further, authors Kuete V, Dzotam JK, Falcao-silva VD, Gibbons S, Kuiate JR, Mbaveng AT, Tankeo SB and Voukeng IK are the major contributors and productive authors.


INTRODUCTION
The discovery of Antibiotic penicillin in the 19 th century and subsequent development of other antibiotics such as streptomycin, sulphonamides and chloramphenicol was most important discoveries in the medicine with remarkable reduction in the morbidity and mortality rate due to infectious diseases. This was the start of the "Antibiotic era" with dramatic impact on the whole practice of medicine for common infections and as well controlling the secondary infections that occur during complicated hospital procedures such as surgery, organ transplantation, renal dialysis, cancer chemotherapies [1].
As per the World Health Organization (WHO) report, during the year 2000 and 2015, global antibiotic consumption has increased by 65% in humans whereas use of antibiotics in animals to improve the animal products has been increased by 11.5% [2]. Moreover, antibiotics have often been perceived as "magic bullets", and requested for every febrile episode. Unfortunately, these inappropriate perceptions about antibiotic and antibiotic overuse, irresponsible agricultural practices of using farm antibiotics to avoid plant diseases, using antibiotics to treat or prevent diseases in animals, further contributes to the emergence of MultiDrug Resistance Bacteria (MRB).
Based on aforementioned details, it is evident that the infections due to MRB are one of the biggest threats to public health with an annual mortality rate of 700000 worldwide. To make matters worse, COVID-19 pandemic is paving the way for MRB, typically due to increased prescriptions and dispensing of antibiotics, though COVID-19 is caused by SARS-CoV-2 virus and not by bacteria.
As per the Resistance map developed by the Center for Disease Dynamics Economics and Policy (CDDEP), above mentioned bacteria shows average resistance of 50 to 80% to penicillin"s like ampicillin, amoxicillin, thirdgeneration cephalosporins and fluoroquinolone and even to combinations antibiotics such as amoxicillin-clavulanic acid [4].
In contrast to the urgent need of antibiotics to manage the MDR bacterial infections, the rate at which new antibiotics were discovered steadily declined. Between 2003 and 2007, only five antibiotic agents were approved by the US Food and Drug Administration, the lowest number in 10 years. PAW report, shows that 41 antibiotics are in development out of which 15 were in Phase 1 clinical trials, 12 in Phase 2, 13 in Phase 3, 1 has had a new drug application submitted, 4 have been approved till December 2019 [5].
To manage MRB, various strategies were developed by governments of different countries such as providing funding for the development of new antibiotic molecules as well as for studying the resistance mechanism in bacteria. However, development of new antibiotics is time consuming and furthermore, even for new antibiotics bacteria may develop a resistance. In contrast, studies on bacterial resistance mechanisms paved the way for quick and effective solutions to manage MRB. The studies show that efflux pumps present on cell walls of the resistant bacteria are responsible for extrusion of the antibiotic out of the bacterial cell and thereby reducing its effectiveness. Accordingly, use of Efflux Pump Inhibitors (EPI) as antibiotic adjuvants is recommended in the management of the MRB. Moreover, use of EPI as adjuvant for antibiotic retains the effectiveness of the available antibiotics and thereby reduces the burden of immediate requirement of new antibiotic for MRB [6,7].
Various studies in search of EPIs showed that phyto constituents such as piperine, curcumin, reserpine, gingerol, shagol, quercetin, rutin has potential to block the efflux pump in MRB and thereby maintaining the effectiveness of the antibiotics against MRB. The successful launch of Resorine by Cadila Pharmaceutical as antituberculosis drug comprising combination of antibiotics (Rifampicin-200 mg, Isoniazid-300 mg) and EPI (Piperine-10mg), which has further created boost in the scientific world to analyze potential of various phyto-constituents of medicinal plants [8].
However, till today, other than Resorine, not a single antibiotic adjuvant combination is available in the market. Accordingly, the present paper is focused on providing a systematic review of the literature covering aspects such as mostly studied phyto-constituents as EPI or antibiotic adjuvant, MDR bacteria and the like. Further there is unmet need to conduct a bibliometric analysis to understand the impactful author, journal, in the area of antibiotic phytoconstituent combination.

Objective
The fundamental purpose of the study is to analyze the predominant literature depicting the plant phyto-constituents as a bacterial EPI and adjuvant for antibiotics in the management of resistant bacterial infections.
Apparently, following objectives decoding the scope of the study are devised.

REFINING OF RETRIEVED LITERATURE
The present study was aimed to focus on research articles published during the period of 1996-2021.
The review articles, short communications, and conference papers were excluded to avoid the research bias. Duplication in the retrieved literature was removed using conditional formatting of MS-Excel.

Analysis Protocol
The literature 221 obtained after removing the duplication was reviewed and 37 research articles depicting efflux pump inhibiting plant phyto-constituents as adjuvant for antibiotics were shortlisted for the present study. The research articles screening phyto-constituents as EPIs but not explicitly elaborating on its combination with antibiotics are rejected.
The content analysis of the shortlisted 37 research articles was conducted to cluster the articles into knowledge structures such as type of bacteria, combination of antibiotics and plant phyto-constituents as adjuvant, classification of the antibiotics as per their mechanism of action and chemical classification of plant phytoconstituents.
A comprehensive bibliometric analysis of the shortlisted 37 articles was conducted to obtain the publication trend, prolific authors and their affiliated institute and countries. Author and index keyword analysis was conducted to explore the prevalent keyword in the management of antibiotic resistance using plant phytoconstituents as antibiotic adjuvant. A Prisma chart elaborating on Protocol for systematic review is portrayed in Fig. 1.

Analysis Softwares Used
Pivot table tool of Microsoft Excel is used to evaluate the outcomes of the content analysis of the 37 shortlisted articles. Softwares like Raw Graphs and R-tool-Bibliometrix, Biblioshiny is used to comprehensively map the prolific authors and journal and the relatedness for Citation.

Content Analysis
Total 37 research articles, illustrating the combination of plant phyto-constituents with antibiotics in the management of bacterial infections by way of efflux pump inhibition were selected for the content analysis. The focal point of the analysis was to understand the relationship between the type of the antibiotic and plant phyto-constituents as adjuvant, frequently studied bacteria for the antibiotic adjuvant combination, structural similarity between the phyto-constituents used as antibiotic adjuvants.

List Antibiotics studied per Articles
Antibiotics that inhibit bacterial Protein synthesis Antibiotics that Inhibit bacteria DNA Synthesis Antibiotics that inhibit bacterial cell wall Synthesis Antimycobacterial Agents
The structural elucidation of these Phytoconstituents as per Table 1 shows that the presence of either Two co-planar aromatic rings, a positively charged Nitrogen Group, or a Carbonyl group and are belonging to class of alkaloids, anthocyanins, anthraquinones, flavonoids, phenols, saponins, tannins, sterols and triterpenes are frequently studied as antibiotic adjuvants [ 2,9-40, 41,42].
The analysis of the 37 shortlisted papers, also indicates that the 95% of papers evaluated the potential of the plant total extract whereas only 5 % papers are elaborating the potential of isolated phyto-constituents as antibiotic adjuvants. The plant extracts are preferred owing to its synergistic effect typically due to the presence of mixture of phyto-constituents belonging to classes such as alkaloids, anthocyanins, anthraquinones, flavonoids, phenols, saponins, tannins, sterols and triterpenes, as compared to the isolated phyto-constituent belonging to only one of the classes.
The content analysis of the shortlisted articles 33 plants are studied for its EPI. Further, segregation of these plants based on the families indicates that Rutaceae, Lauraceae, Anacardiaceae, and Annonaceae are mostly studied families. The 37 publications analyzed are dispersed across 24 journals and 6 subject areas. Fig. 4 depicts that 26 are published in the journals covered under the subject area Medicine followed by Immunology and microbiology (16), Biochemistry, Genetics and Molecular Biology (10), Pharmacology, Toxicology and Pharmaceutics (08). Further, the total citation score indicates that articles and journals covered under the Medicine subject area are creating a greater impact on the scientific community than other subject areas [2,.

Publication Trend
After analyzing the impact of each subject area on the scientific community, the analysis of the citation score of the individual journal as shown in Fig. 5  However, comparison between the no. of papers published and the citation score as per Fig. 4 indicates that though the journals like Journal of Antimicrobial Chemotherapy [43] and Antimicrobial Agents and Chemotherapy [44], has published only 4 and 2 articles respectively, but the citation score is higher than BMC Complementary and Alternative Medicine, directing that for the subject area Medicine, Antimicrobial Chemotherapy and Antimicrobial Agents and Chemotherapy has greater impact on scientific community. [45]

Top Contributors Based on Their Number of Publications and Citation Score
As per Fig. 6

RESULT AND DISCUSSION
The systematic review of the literature indicates that 221 papers were providing the potential of the plant phyto-constituents as EPIs; however, only 37 papers evaluated the synergistic effect of the EPI for a specific type of antibiotics. Further, 90% of papers are elaborating the potential of alkaloids, anthocyanins, anthraquinones, flavonoids, phenols, saponins, tannins, sterols and triterpenes on Gram negative bacteria such as Acinetobacter baumannii, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa whereas only 10% selected Gram positive (Staphylococcus aureus) for the similar study. Further, majority of the research papers were focused on evaluating the potentials of EPI along with the Fluoroquinolone antibiotics, specifically, ciprofloxacin. Moreover, majority of the articles evaluated antibiotic adjuvant combinations for the antibiotics which inhibit the protein synthesis like tetracycline, erythromycin and Chloramphenicol.
With respect to citation score of the shortlisted papers, Kuete, V is the most prolific author and the Journal of Antimicrobial Chemotherapy, Antimicrobial Agents and Chemotherapy BMC Complementary and Alternative Medicine are the most productive journal. The subject area wise segregation of shortlisted article shows that authors are preferring subject area Medicine to publish the papers. Moreover, the journals published under the subject area Medicine showed higher impact on the scientific community as correlative to its higher citation score.   To tackle the issue of No antibiotic era and the multi drug resistant bacterial infections various strategies such as responsible prescribing of the antibiotics, development of new antibiotic molecules as well as perusing the resistance mechanism in bacteria are adopted by the government and the research scientist. Amongst these strategies, studies on bacterial resistance mechanisms may paved the way for quick and effective solutions to manage MRB.
Accordingly, present paper provided systematic review and the bibliometric analysis on plant phyto-constituents as Antibiotic Adjuvants. The systematic review and the content analysis of three cluster indicates that the Antibiotics such as Ciprofloxacin, Norfloxacin, Tetracyclines and Chloramphenicol can appropriately be combined with plant phyto-constituents such alkaloids, terpenoids, flavonoids to inhibit the efflux pump of Gram negative bacteria, and Gram Positive .