An invited review published in Applied Biological Chemistry examines the complex relationship between the botanical origins of bee-derived propolis and its potential clinical applications. The study, conducted by researchers Kwanyong Choi and Ji Yeon Kim, critically evaluates current human evidence regarding oral propolis supplementation. The authors argue that the clinical translation of propolis as a nutraceutical is significantly complicated by substantial chemical variability associated with its geographical and botanical sources. This variability prevents direct comparisons among studies and limits the ability to establish reliable dose-response or chemotype-specific interpretations.
Propolis is a resin-like material produced by social bees, including honeybees and stingless bees, from plant exudates and bud resins. It is blended with wax and salivary secretions to form a highly adhesive matrix used to seal crevices and protect the colony from bacteria, parasites, and fungi. The gross composition of crude propolis varies substantially according to botanical origin, geographical location, season, and bee species. Chemical analyses have revealed several hundred distinct constituents, including benzoic and cinnamic acid derivatives, terpenes, aromatic aldehydes, and fatty acids. This molecular complexity means that propolis cannot be treated as a single uniform substance.
The review categorizes propolis into simplified chemotypes based on botanical origin and dominant chemical patterns. Poplar-type propolis is predominant in temperate climates, including much of Europe, parts of North America, and large areas of China and Korea. This type is consistently rich in flavonoid aglycones such as pinocembrin, chrysin, and quercetin, as well as hydroxycinnamic acids. In contrast, tropical-type propolis from Brazil has quite different botanical origins. Brazilian green propolis is derived mainly from the shrub Baccharis dracunculifolia and is characterized by a high content of prenylated cinnamic acid derivatives, particularly artepillin C. Brazilian red propolis, produced in northeastern coastal areas, is characterized by an isoflavonoid-rich profile including formononetin and daidzein.
To assess the clinical relevance of these variations, the researchers conducted a comprehensive literature search across major electronic databases, including PubMed, Scopus, and Web of Science. They identified fourteen randomized clinical trials involving orally administered propolis. The methodological quality of these trials was assessed using the Cochrane Risk of Bias 2 tool. Eleven of the included trials were judged to have a low overall risk of bias, two raised some concerns, and one was judged to have a high risk of bias. The study by Duarte Silveira et al. showed concerns related to the randomization process and the selection of reported results, leading the authors to interpret its findings cautiously.
The clinical evidence reviewed is concentrated mainly in presumed Iranian poplar-type propolis and Brazilian green propolis. In adults with type 2 diabetes mellitus, Iranian propolis administered at 900 or 1000 mg per day for 12 weeks improved selected indices of glycemic control and insulin resistance. These improvements included reductions in postprandial glucose, fasting insulin, and the Homeostatic Model Assessment for Insulin Resistance, or HOMA-IR. In adults with metabolic syndrome, propolis supplementation at 500 mg per day for 12 weeks significantly reduced waist circumference, although other metabolic syndrome components were not significantly affected. These findings suggest that propolis may influence glycemic regulation and abdominal adiposity in specific metabolic phenotypes.
Additional trials have evaluated propolis in autoimmune, renal, and respiratory conditions. In women with rheumatoid arthritis, Iranian propolis at 1000 mg per day for 12 weeks reduced high-sensitivity C-reactive protein, or hs-CRP, and improved selected lipid-related cardiovascular risk indices. In adults with moderate persistent asthma, Iranian propolis at 225 mg per day for 4 weeks increased forced expiratory volume in one second and reduced fractional exhaled nitric oxide and eosinophilic airway inflammation. These results align with the airflow-limitation and type 2 inflammatory phenotypes of asthma, although longer-term effects on exacerbations were not established.
During the COVID-19 pandemic, two Brazilian trials evaluated standardized Brazilian green propolis in hospitalized patients. The reported reductions in hospital stay or secondary infection rate represent clinically relevant outcomes, although mortality and several other clinical endpoints were not significantly different between the groups. In chronic kidney disease, Brazilian green propolis at 500 mg per day for 12 months reduced proteinuria and urinary monocyte chemoattractant protein-1 without altering estimated glomerular filtration rate. The unchanged estimated glomerular filtration rate indicates that an improvement in filtration function was not demonstrated during the intervention period, despite the reduction in markers of renal injury.
In reproductive health, propolis supplementation has been associated with changes in selected outcomes aligned with male infertility and polycystic ovary syndrome phenotypes. In men with asthenozoospermia, Iranian propolis at 1500 mg per day for 10 weeks significantly increased sperm count, concentration, and total sperm motility. In women with polycystic ovary syndrome, propolis supplementation at 500 mg per day for 12 weeks significantly reduced fasting insulin, HOMA-IR, and total testosterone. However, the trial did not determine whether these changes improved ovulation, menstrual regularity, fertility, or other patient-centered outcomes. The reliance on surrogate biochemical markers rather than direct clinical endpoints remains a significant limitation in this area of research.
Propolis has also been investigated in relation to the inflammatory and oxidative responses to intense exercise. In young male athletes, Iranian propolis at 900 mg per day for 4 weeks significantly reduced interleukin-6, malondialdehyde, and total oxidant status. While these changes indicate modulation of the inflammatory and redox responses, maximum oxygen uptake, anaerobic power, and body composition did not differ significantly between the groups. The observed biochemical effects were therefore not accompanied by improvements in exercise performance or body composition, highlighting the distinction between biological markers and functional clinical outcomes.
A major limitation identified in the review is the inconsistent chemical characterization and standardization of the propolis preparations used in clinical trials. A small number of studies employed standardized preparations, whereas many trials used regional propolis products without reporting detailed marker compound concentrations or complete compositional profiles. This lack of standardization makes it difficult to determine whether the observed effects were associated with a particular chemotype or specific marker compounds. The biological activity of propolis cannot be assumed to be interchangeable across botanical and geographical origins, yet the current evidence base lacks the analytical rigor to establish reproducible relationships between chemical composition and human outcomes.
The generalizability of the available evidence is further limited by its geographical and compositional concentration. Most clinical studies evaluated Iranian poplar-type propolis or Brazilian green propolis, whereas other propolis chemotypes and geographical origins have received little clinical investigation. Geographical origin was closely associated with the clinical populations studied, making it difficult to distinguish effects related to propolis origin from those related to the underlying clinical phenotype. Many clinical trials also lacked detailed constituent profiling and batch-level standardization, meaning the current findings apply primarily to the specific preparations and populations evaluated and should not be generalized to all propolis products.
Safety reporting represents another important limitation of the current clinical evidence. Although standardized propolis preparations were generally described as well tolerated in several short-term trials, adverse events and clinically relevant laboratory safety measures were not consistently evaluated. Allergic reactions remain the most clearly recognized safety concern because propolis contains complex mixtures of resin-derived constituents that may cause hypersensitivity reactions in susceptible individuals. The relatively small sample sizes and short intervention periods of the available trials limit the detection of uncommon, delayed, or cumulative adverse effects, leaving long-term safety and safety in special populations insufficiently characterized.
Based on the current human evidence, the authors conclude that propolis should be regarded as a candidate bioactive ingredient for further nutraceutical development rather than an intervention with established clinical efficacy. The available findings provide biological plausibility for further investigation but do not establish consistent benefits in symptoms, disease progression, or long-term health outcomes. Future studies should use chemically characterized and standardized preparations and evaluate clinically meaningful outcomes alongside relevant mechanistic markers to bridge the gap between compositional diversity and clinical translation.
Subject of Research: Compositional variability of bee-derived propolis and its impact on clinical evidence and nutraceutical applications
Article Title: Botanical origin and compositional variability of bee-derived propolis in relation to current clinical evidence and nutraceutical applications
Article References: Choi, K., & Kim, J. Y. (2026). Botanical origin and compositional variability of bee-derived propolis in relation to current clinical evidence and nutraceutical applications. Applied Biological Chemistry, 69(1), Article 62. https://doi.org/10.1186/s13765-026-01132-y
Image Credits: AI Generated
DOI: 10.1186/s13765-026-01132-y
Keywords: propolis, nutraceuticals, botanical origin, clinical trials, bee products, chemical variability, applied biology, inflammation, metabolic health, standardization, Botanical, origin
News Source: Bethany Barker. (November 10, 2026). Propolis Variability Limits Clinical Evidence for Nutraceutical Use. Scienmag.
