Diabetes is a prevalent endocrine disorder that affects millions of people worldwide. Characterized by elevated blood sugar levels, diabetes is not just a sugar metabolism issue but also a gateway to a cascade of complications such as retinopathy, cataracts, atherosclerosis, neuropathy, nephropathy, and impaired wound healing. These complications are primarily linked to the accumulation of Advanced Glycation End Products (AGEs) within human tissues. The formation of AGEs is a consequence of the non-enzymatic glycation process, where reducing sugars react with free amino groups of proteins. This reaction leads to the formation of a reversible Schiff base, which undergoes the Amadori rearrangement to form stable Amadori products. These products further react to form AGEs, which are associated with oxidative stress and inflammation, causing damage to organisms. In light of this, the search for effective AGE inhibitors has become crucial in preventing these complications.
The Magical Properties of Propolis
Propolis, a resinous substance collected by bees from various plant species and mixed with their salivary secretions, has been used in folk medicine since ancient times. It is known for its antimicrobial, antifungal, anti-aging, anticancer, anti-inflammatory, and antioxidant activities. Recent research has also highlighted the anti-glycation effects of propolis. These functional properties can be attributed to the presence of over 300 natural bioactive compounds, mainly including flavonoids, phenolic aldehydes, and terpenoids. The bioactive compounds in propolis vary significantly depending on geographical and botanical origins. For instance, Brazilian green propolis is predominantly composed of artepillin C and terpenoids; red propolis in Mexico is composed of flavanones, isoflavans, and pterocarpans; aspen propolis from northern regions of Europe is composed of flavonoids and phenolic acids. In recent decades, China has emerged as a prominent global producer of propolis, with multiple studies indicating that the Chinese propolis belongs to the poplar-type, meaning the primary plant origin of Chinese propolis is the Populus species.
Research Focus and Findings
The study aimed to investigate the inhibitory potential of various aqueous ethanol extracts of poplar-type propolis on AGEs and oxidative modifications in bovine serum albumin (BSA)-glucose and BSA-methylglyoxal models. The results revealed that these propolis extracts exhibited significant effectiveness in inhibiting the formation of total AGEs, pentosidine, and Nε-carboxymethyllysine (CML). Notably, 75% ethanol extracts of propolis (EEP) exhibited the highest inhibitory activity, surpassing the chemical inhibitor aminoguanidine (AG).
Antioxidant Capacity of Propolis Extracts
The investigation also discovered that these propolis extracts can effectively inhibit oxidative modification, based on measuring the levels of carbonyl and thiol groups and analyzing tryptophan fluorescence quenching. The remarkable anti-glycation potency of aqueous ethanol extracts of poplar-type propolis can be attributed to their elevated contents of phenolic compounds, especially abundant flavonoids, which inhibit the formation of AGEs by scavenging free radicals, decreasing the levels of reactive oxygen species (ROS), and capturing reactive carbonyl species (RCS) in the protein glycation process.
Conclusion and Future Prospects
Our findings indicate that poplar-type propolis may be a potential AGE inhibitor and could be used to develop functional foods and nutraceuticals to prevent diabetic complications. In the future, we will focus on clinical trials to evaluate the efficacy of poplar-type propolis in inhibiting AGEs in vivo, providing reliable evidence for the development of novel propolis nutraceuticals aimed at preventing and treating chronic diseases associated with AGEs.
The Science Behind Propolis and AGEs
Propolis has been a subject of interest due to its potential health benefits. The study mentioned earlier delved into the specifics of how propolis can combat AGEs, which are a group of diverse chemical structures that include both fluorescent and non-fluorescent compounds. These compounds are formed when proteins and fats react with sugars in a process called glycation, which is a natural part of aging but is accelerated in people with diabetes.
The Role of Flavonoids in Propolis
Flavonoids are a class of plant compounds known for their antioxidant properties. They are found in many plants and are responsible for the colorful pigments in flowers, fruits, and vegetables. In the context of propolis, flavonoids are thought to be the primary agents that give it its anti-glycation properties. They work by scavenging free radicals and trapping reactive carbonyl species, which are known to contribute to the formation of AGEs.
The Importance of Antioxidants in Combating Oxidative Stress
Oxidative stress is a state where the balance between free radicals and antioxidants is disrupted, leading to potential damage to cells and tissues. Antioxidants are substances that can neutralize free radicals and prevent this damage. Propolis, with its high content of flavonoids, acts as a potent antioxidant, helping to reduce oxidative stress and protect against the harmful effects of AGEs.
How Propolis Inhibits AGE Formation
The study demonstrated that propolis extracts, particularly the 75% ethanol extract, had a significant inhibitory effect on the formation of AGEs. This was measured by the reduction in fluorescence intensity, which is indicative of the presence of AGEs. The extracts were also able to reduce the levels of carbonyl groups, which are markers of protein oxidation, and increase the levels of thiol groups, which are essential for maintaining protein structure and function.
The Potential of Propolis in Functional Foods and Nutraceuticals
Given its anti-glycation properties, propolis has the potential to be incorporated into functional foods and nutraceuticals. These are foods and dietary supplements that provide health benefits beyond basic nutrition. By including propolis in these products, it may be possible to create a natural defense against AGEs and the complications associated with diabetes and other chronic diseases.
Future Research and Clinical Trials
While the study provided promising results, further research is needed to confirm the efficacy of propolis in vivo. Clinical trials will be crucial in determining the effectiveness of propolis as an AGE inhibitor in humans. This will involve testing propolis supplements on human subjects and monitoring their impact on AGE levels and overall health.
Conclusion
Propolis, with its rich content of flavonoids and other bioactive compounds, shows great promise as a natural anti-glycation agent. Its ability to inhibit the formation of AGEs and protect against oxidative stress makes it a valuable candidate for the development of functional foods and nutraceuticals aimed at preventing and treating diabetes-related complications. As research continues, we can look forward to a future where natural remedies like propolis play a significant role in managing and mitigating the effects of chronic diseases.
Citation
Wang, G.; Zhang, Y.; Qiao, J.; El-Seedi, H.R.; Kong, L.; Zhang, H. Inhibitory Effects of Aqueous Ethanol Extracts of Poplar-Type Propolis on Advanced Glycation End Products and Protein Oxidation. Foods 2024, 13, 3022. https://doi.org/10.3390/foods13193022
