The total number of publications on quercetin nanotechnology is 209 from January 2019 to December 4th, 2024. In this bibliometric study, the type of publications included 122 articles and 96 reviews. The two proceeding papers and book chapters are excluded respectively. Figure 1 depicts a light purple bars and dark purple line chart visualizing research trends on quercetin nanotechnology in academic publications and citations for the period from 2009 to 2024 respectively. Briefly, between 2009 and 2013, the number of publications remained relatively low, with fewer than 5 papers published annually. This result suggests that from 2009 to 2013 as an early exploration phase for quercetin nanotechnology as researchers were investigating foundational aspects of quercetin. Based on the total number of citations, the citations also followed a gradual increase from 2009 to 2013, correlating with the number of publications, however, the citations remained relatively modest.

A gradual increase in publications can be observed from around 2014 to 2018, reaching approximately 10 papers annually. A significant rise in publications began around 2019 with a notable surge in 2020 reaching over 20 publications. Total citations also grew steadily parallel to the rise in publications. The increasing number of publications and citation counts reflects a growing recognition and validation of quercetin nanotechnology’s potential in scientific and clinical communities. The highest number of publications occurred in 2021 and 2022 with around 35 to 40 publications. A slight dip in 2023 and 2024 suggests stabilization but maintains a high number of publications above 30. The peak rise in publications reflects the maturation of quercetin nanotechnology as a research field. Furthermore, from 2018 till 2023, the total citations grew sharply with over 1100 citations, while 2023 shows a slight decrease in publication however the total citations likely to stabilize in the number of publications but still maintain a high number of total citations over 1000. In 2024, the number of publications demonstrated a significant increase, reaching 39 publications and accumulating over 1,200 total citations. Within this period, researchers likely began focusing on more sophisticated applications in health, such as targeting oxidative stress, inflammation, and chronic diseases. The sharp rise in citations during this time also indicates the field's growing impact on broader scientific disciplines, including nanomedicine, pharmacology, and clinical applications.

In order to explore the research trend of the topic, it is essential to utilize credentials and impactful papers as sources of references. Table 1 highlights the top 10 of highly cited articles found using “quercetin nanotechnology” as a keyword. Based on the data, it is evident that the most cited articles were mostly from 2014, as the top four articles were found within that year. The titles of the top articles are (1) Nanotechnology-based drug delivery systems and herbal medicines: a review written by (Bonifácio et al. 2014) in International Journal of Nanomedicine with total citation of 429; (2) Application of nanotechnology in improving bioavailability and bioactivity of diet-derived phytochemicals written by (S. Wang et al. 2014) in the Journal of Nutritional Biochemistry with total citation of 312; (3) Delivery of anti-inflammatory nutraceuticals by nanoparticles for the prevention and treatment of cancer written by (Nair et al. 2010) in the journal of Biochemical Pharmacology with total citation of 191; (4) Quercetin and gallic acid mediated synthesis of bimetallic (silver and selenium) nanoparticles and their antitumor and antimicrobial potential written by (Mittal et al. 2014) in the journal of Journal of Colloid and Interface Science and (5) Quercetin-nanostructured lipid carriers: Characteristics and anti-breast cancer activities in vitro written by (D. D. Sun et al. 2015) published in the journal of Colloids and Surfaces B: Biointerfaces The first two articles mainly emphasized on the integration of nanotechnology to enhance the delivery, bioavailability and therapeutic properties of natural phytochemicals. The latter three articles focus on the development and formulation of quercetin-based nanoparticles and nanostructures in treating cancer or tumor. Overall, these articles open a research avenue on the general potential of nanotechnology in enhancing drug delivery efficiency through phytochemicals including quercetin. Therefore, most researchers will refer to these articles as main references to further elaborate on the overview of the development of quercetin nanotechnology before discussing their respective niche topics. The rest of most cited articles covered the advancement of quercetin nanotechnology such as the efficiency potential of quercetin nanostructured lipid carriers, nanoencapsulation of quercetin, metal-based quercetin, and quercetin loaded polymeric nanoparticles in cancer therapy as listed in Table 1 These findings suggest a strong research interest in using quercetin within nanotechnology for medical applications, particularly in cancer therapy and bioactivity enhancement.

This world map visualizes the distribution of scientific articles related to quercetin nanotechnology across various countries (Fig. 2). The total number of countries contributing to quercetin nanotechnology publications is 17 countries. Each country is color-coded and labelled with the number of articles they have contributed to this research area. India is the leading contributor to research on quercetin nanotechnology, with the highest number of published articles with 60 publications and total publications. China ranks second with 32 publications, significantly contributing to the body of knowledge in this area. Saudi Arabia, the USA, Iran, and Italy are also major contributors with 23, 21, 20, and 19 publications respectively. Brazil, Egypt, England, and Malaysia have also shown significant research activity in quercetin nanotechnology, contributing more than 10 publications since 2009. These findings demonstrate that quercetin nanotechnology is a field of growing global research interest.

Table 2 presents the leading 10 countries ranked by the total number of publications, citations, and their respective H-index. The H-index serves as a metric to evaluate the productivity and citation impact of these publications. However, based on total citations and H-index values, India, China, the USA, and Italy are the leading countries, with H-index scores ranging from 18 to 13, reflecting the high quality of their research output. India and China lead with the highest number of publications and citations. The high H-Index of 18 and 14 suggests that many publications from India and China are highly cited respectively, indicating consistent research quality across a large number of papers. Knowing that India and China recorded the highest population in the world, possibly both countries have massive cases, experiences, and occasions where quercetin was involved. Historically, the use of plant extract in traditional India medicine such as Ayurveda and traditional Chinese medicine in China has provided strong foundation for modern research (Patwardhan et al. 2005). Through these experiences, the advancement in quercetin including nanotechnology aspect has begun earlier and thus their information, knowledge and technology are considerably advanced and reliable. The USA and Italy have a lower number of publications which are 21 and 19 respectively but a large number of citations, indicating higher quality or impactful research. The H-Index is relatively high which is 13 considering the lower publication count, showing that its fewer papers are more consistently cited. Countries like Saudi Arabia and Iran may have moderate H-Index because while they produce many papers, fewer papers receive high citation counts, limiting the H-Index's growth. Countries with higher H-index values generally demonstrate significant investment in research infrastructure and allocate substantial funding to support research activities. This investment facilitates the production of higher-quality publications, as researchers benefit from enhanced tools, facilities, and support systems. The higher H-index also signifies that a considerable proportion of publications are not only successfully disseminated but are also frequently cited on a global scale, indicating the substantial influence and widespread recognition of the country’s research contributions.

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The most influential source title for quercetin nanotechnology was evaluated based on six criteria: total publications, total citations, 5-year impact factor, journal impact factor quartile, journal citation indicator (JCI), and Eigen factor. Total publications and citations are sum from 2009 till October 2024. From Table 3, the Journal of Drug Delivery Science and Technology has published the highest number of publications which is 9 with total citation of 115 on the topic of quercetin nanotechnology. The International Journal of Nanomedicine stands out with 829 total citations, 8 publications, and 75 citations per year indicating its influential and impactful publications annually on the topic of quercetin nanotechnology.

Most all the top 10 sources of publications on quercetin nanotechnology ranked in quartile Q1 and Q2. The journal ranked in Q1 is in the top 25% meanwhile, journals ranked in Q2 such as Molecules and Applied Sciences-Basel are in the top 25% to 50% of journals in its field based on their Impact Factor. Both Q1 and Q2 journals are known for their rigorous peer-review processes, high-quality and impactful journals. The fact that quercetin nanotechnology research is predominantly published in these journals suggests that the research in this area is of high quality and meets the stringent criteria for publication in leading journals.

The 5-year Impact Factor is the average number of times articles from the journal published in the past five years have been cited in the JCR year. It is calculated by dividing the number of citations in the JCR year by the total number of articles published in the five previous years. The Journal of Nanobiotechnology has the highest impact factor at 11.4, indicating that articles in this journal have been heavily cited over five years.

The Journal Citation Indicator (JCI) is the average Category Normalized Citation Impact (CNCI) of citable items (articles & reviews) published by a journal over a recent three-year period. The average JCI in a category is 1. Journals with a JCI of 1.5 have 50% more citation impact than the average in that category. The Journal of Nanobiotechnology has the highest JCI at 1.71, followed by the International Journal of Pharmaceutics with JCI of 1.63 and Biomedicine & Pharmacotherapy with JCI of 1.57 implying this journal is more influential and older relative to other journals in the same field.

The Eigen factor Score reflects the density of the network of citations around the journal using 5 years of cited content as cited by the current year. It considers both the number of citations and the source of those citations so that highly cited sources will influence the network more than less cited sources. The Eigen factor calculation also does not include journal self-citations. The International Journal of Molecular Sciences has the highest Eigen factor score was 0.4308 followed by Molecules with an Eigen factor was 0.1712 on the topic of quercetin nanotechnology, which indicates both are highly influential in the academic community or across multiple fields, despite its lower JCI and impact factor.

Most publications on quercetin nanotechnology appearing in Q1 and Q2 journals strongly indicate the field’s scientific significance, high quality, and broad influence. This reflects the advanced nature of the research, its recognition by leading scholars, and its substantial impact on nanotechnology, biotechnology, and medicine. Based on 5-year impact factors, JCIs, and average citations per year, the Journal of Nanobiotechnology and the International Journal of Nanomedicine are ideal channels for research in quercetin nanotechnology, as they offer both immediate citation impact and greater visibility. Additionally, journals with high Eigen factor scores, such as the International Journal of Molecular Sciences, offer long-term influence beyond short-term citation metrics, making them valuable for multidisciplinary research impact.

A total of 695 keywords were obtained from the Author's co-occurrence keywords. The minimum number of co-occurrences of these keywords to be displayed in Fig. 3 was set at ‘3’. This makes 52 keywords meet the threshold. Figure 3 displays the density visualization on the Author’s keyword co-occurrences within the topic of quercetin nanotechnology. The density visualization map provides key research areas and relationships related to quercetin nanotechnology based on co-occurrences of Authors' keywords in publications. In a bibliometric density visualization, the colours represent the density of occurrences or co-occurrences of certain terms in the analysed body of literature. Each colour indicates how frequently the terms are found together in the research papers.

Virtually, three main-coloured clusters are three main-coloured clusters that can be observed in this density visualization. First is a red-coloured cluster representing high-density regions containing quercetin and nanotechnology as the core area and main focus of the research hotspot. Next, is yellow-coloured cluster indicates a moderately high density of co-occurrence that linked to the research's main core are phytochemicals, cancer, nanomedicine and nanocarriers indicating that research on quercetin nanotechnology is mainly focused in the application of cancer therapy. The yellow cluster also consists of nanoparticles, antioxidants, drug delivery, curcumin, bioavailability, and flavonoids. This suggests a significant focus on improving the bioavailability and delivery of quercetin as flavonoids that have antioxidant properties through encapsulation of the quercetin in nanoparticles.

Next, the green cluster represents moderate density meaning that keywords in this cluster are well discussed in the literature but not as frequently as the red and yellow clusters. The keywords in the green cluster include anticancer, green synthesis, oxidative stress, apoptosis, polyphenols, nutraceuticals, and neurodegeneration. These keyword co-occurrences indicated the broader application of quercetin nanotechnology in treating oxidative stress and Alzheimer’s through nutraceuticals. This cluster also represents the green synthesis of nanoparticles from quercetin as a sustainable and safe approach for cancer treatment.

Lastly, the light blue cluster indicates a low-density research area meaning these keywords are less frequently discussed in the literature yet suggest emerging or niche areas of research that can be further explored in the future. Keywords such as nano formulations, hyaluronic acid, essential oil, berberine, gold nanoparticles, silver nanoparticles, wound healing, antimicrobial, blood-brain barrier, nanomaterials, liposomes, diabetes, cancer therapy, natural compounds neurodegenerative disorders and Parkinson’s disease. These keywords could represent more specialized and newer research areas where the role of quercetin nanotechnology is being explored to a lesser extent and not established as the central theme yet. These findings could open potential avenues of research on quercetin nanotechnology.

Figure 4 illustrates the thematic evolution through the advancement and progression of research on quercetin nanotechnology specifically for health science applications. Starting in 2009 to 2010, first publication titled “Nano dispersion of quercetin and ferulic acid by (Pourmorad et al. 2009). The theme of nanotechnology stands out as the central theme marking the early stages of applying this quercetin nanotechnology as a therapy method. In their study, the nanosized droplet of quercetin and ferulic acid was successfully prepared by solvent diffusion method in organic phase and lecithin. They found the droplet size of the quercetin and ferulic acid were 298 ± 14 and 289 ± 14 nm respectively. Their findings are consistent with the work done by Liao et al., demonstrating that the formation of nano emulsion droplets enhances the performance of quercetin compared to its original form (Liao et al. 2010).

Later, from 2013 to 2014, the theme of nanotechnology continued to dominate, with the theme of flavonoids as quercetin belongs to the family of flavonoids, specifically flavanols. These two main themes indicated the growing interest in combining these natural compounds with nanotechnology. Within these years, the application of nanotechnology has been successfully demonstrated to enhance bioactivity of diet-derived phytochemicals such as quercetin, resveratrol, curcumin and epigallocatechin (S. Wang et al. 2014)(Aras et al. 2014)(Bothiraja et al. 2014)(S. P. Wang et al. 2013).

From 2015 to 2018, significant advancements were made in quercetin nanotechnology research, with emerging themes focusing on bioavailability, drug delivery, and neurodegeneration, while quercetin and nanotechnology remained central to the research. These research themes show a clear emphasis on improving the bioavailability of quercetin by using nanotechnology (Li et al. 2015). The application of quercetin nanotechnology in drug delivery was also a prominent focus during these years. For instance, Xu et al revealed by quercetin-loaded MPEG-PCL nano micelles as a novel nano agent of quercetin with particle size of 34.8 nm, completely dispersed in the water and released quercetin in a prolonged period in vitro and in vivo (Xu et al. 2015). Several studies reported the quercetin-based nanotechnology could overcome multi drug resistance and site specific action without affecting other organs and tissues (Hädrich et al. 2016)(Kunjiappan et al. 2016)(Xu et al. 2018). Within these years, the theme of neurodegeneration also appeared. This indicates that by conjugating quercetin into nanotechnology as drug delivery system, the bioavailability of quercetin in the brain can be enhanced compared to free quercetin (Najafabadi et al. 2018)(Halevas 2017)(Halevas et al. 2016). This suggests that nanotechnology-enhanced quercetin is being investigated to be utilized for the neurodegeneration treatment in combatting diseases like Alzheimer's and Parkinson’s.

Next, in 2019 to 2023, research themes of quercetin, and drug delivery remain to be critical, with the increased focus on how nanotechnology could enhance the targeting of quercetin to specific disease sites. Several research themes like nanoparticles, essential oil, oxidative stress, and inflammation appeared during this period indicating growing interest in this topic. Oxidative stress results from an imbalance between reactive oxygen species (ROS) and antioxidants leading to tissue or cellular damage that causing inflammation. Integration of quercetin nanotechnology in the form of nanoparticles gain importance, reflecting advancement in the design of nanocarrier by integrating the benefit of quercetin and metal nanoparticles respectively. The development of inorganic nanoparticles by conjugating quercetin was published starting in 2014, the appearance of nanoparticles within this region could be resulted of the usage of keywords by Authors. Several metal nanoparticles were synthesized from quercetin such as silver-selenium (Mittal et al. 2014), gold(Milaneze et al. 2016)(Milanezi et al. 2019), silver (Panneerselvam et al. 2016) (Aiswarriya et al. 2023), titanium dioxide (Gulla et al. 2021) palladium (Piñón-Castillo et al. 2021), Iron (III) (Nathupakorn et al. 2022). However, the toxicity and safety concerns associated with metal nanoparticles have been a subject of ongoing debate. Essential oil appears to this period indicated an alternative therapeutic agent other than quercetin that can be conjugated with nanotechnology. As reported by Hafez et al the integration of quercetin and essential oil in lipid nano-capsules proved as promising synergistic antifibrotic efficiency on rats with CCL4-induced liver fibrosis (Hafez et al. 2022).

In the latest phase in 2024, the research theme on the topic of quercetin nanotechnology evolved into Alzheimer's disease, cancer, and breast cancer while remained other themes such as inflammation, nanotechnology, nanoparticles and quercetin. This shows the research fully revolves around applied health applications with quercetin nanotechnology being investigated to combat inflammation (Kharbanda et al. 2024) (Syahputra et al. 2024), cancer (Homayoonfal et al. 2023), breast cancer (Mirzaei et al. 2024) and more specific neurodegenerative diseases like Alzheimer's disease (Kamath et al. 2024) (Goyal et al. 2024) (Shelke et al. 2024). The research theme evolution on quercetin nanotechnology has revolved and advanced from addressing basic bioavailability issues to applying quercetin-loaded nanoparticles in treating major diseases, indicating the growing impact of this topic in therapeutic applications.