Propolis Flavonoids: Scientifically Verified Natural Protective Power

Propolis is a resinous substance collected by honeybees from plant buds, sap flows, or other botanical sources, mixed with secretions from their hypopharyngeal and wax glands. Revered internationally as “purple gold,” propolis has an exceptionally complex chemical composition. To date, over 600 compounds have been isolated and identified from propolis, including flavonoids, terpenes, quinones, esters, alcohols, aldehydes, phenols, organic acids, as well as amino acids, enzymes, vitamins, polysaccharides, and a wide range of trace elements. Among these, flavonoids stand out for their abundant variety and remarkable bioactivity, and they are widely recognized as the core material basis for propolis’s biological functions. Propolis is thus hailed as a “treasure house of flavonoid compounds” (Xu et al., 2005), with more than 135 flavonoid compounds identified from propolis samples around the world (Zhang & Hu, 2009).

The health benefits of propolis flavonoids cover multiple aspects, including antibacterial, antioxidant, anticancer, cardiovascular protection, endocrine regulation, and hypoglycemic effects.

Antibacterial and Antiviral Activity
Propolis flavonoids exhibit broad-spectrum antibiotic properties, effectively inhibiting the proliferation of various bacteria and certain viruses. Among them, the flavonoids with the strongest antibacterial activity include galangin, pinocembrin, and pinobanksin. Studies have shown that ethanol extracts of propolis significantly inhibit 25 out of 39 tested bacterial strains. This broad-spectrum antibacterial activity provides a scientific basis for the adjunctive intervention of propolis in infectious diseases.

Antioxidant and Anti-aging Effects
Propolis flavonoids contain substances with relatively low redox potentials, capable of donating hydrogen atoms to effectively scavenge free radicals. Their mechanism of action not only involves direct capture of reactive free radicals but also chelation of metal ions that catalyze oxidation, along with protective effects against ischemia-reperfusion injury and improvement of microcirculation, thereby slowing the aging process (Torjussen et al., 2005; Bertram & Lewis, 1983). In vitro experiments by Nagai et al. (2003) further confirmed that a water extract of propolis at concentrations of 50 mg/mL and 100 mg/mL completely inhibited the generation of peroxides and hydroxyl radicals, demonstrating its potent antioxidant potential.

Anticancer Activity
Studies by Chen et al. (2003) and Benguedouar et al. (2016) have shown that propolis flavonoids can inhibit the proliferation and induce apoptosis of various tumor cell lines, while exhibiting low toxicity to normal cells. This selective action suggests promising application prospects in adjuvant cancer therapy.

Cardiovascular Protection
Propolis flavonoids can prevent the proliferation of collagen fibers in arterial walls and the accumulation of cholesterol in the liver. They also bind to cholesterol or its conversion products (bile acids) to inhibit intestinal absorption and promote degradation and excretion. Additionally, propolis flavonoids have vasodilatory effects and improve smooth muscle contractility, effectively preventing atherosclerosis and significantly reducing triglyceride levels, earning them the title of “blood scavengers” (Yuan et al., 2010).

Endocrine Regulation and Hypoglycemic Effects
Propolis flavonoids exhibit weak estrogen-like activity and can promote the recovery of pancreatic β-cell function, reduce blood glucose and serum cholesterol, improve glucose tolerance, counteract the hyperglycemic effect of adrenaline, and inhibit aldose reductase activity. These actions are valuable for intervening in diabetes and its complications (Yang et al., 2014). Yang et al. (2014, 2015) systematically verified the hypoglycemic effect of total propolis flavonoids using streptozotocin (STZ)-induced and alloxan (ALX)-induced diabetic rat models. They found that total propolis flavonoids significantly lowered blood glucose, improved glycolipid metabolism, suppressed insulin resistance, and promoted the recovery of pancreatic β-cell secretory function. Further studies in spontaneously diabetic rats also confirmed that total propolis flavonoids effectively reduced blood glucose and ameliorated glycolipid disorders.

Tissue Protection and Neuroprotection
Recent research indicates that propolis flavonoids have significant effects on tissue damage protection. Studies by Benguedouar et al. (2016) and Peng & Pan (2010) demonstrated that propolis flavonoids can reduce the extent of cellular and tissue damage under injurious stimuli and enhance tolerance. Notably, propolis flavonoids have also been shown to alleviate cerebral ischemia-reperfusion injury and exert neuroprotective effects, suggesting they could become ideal protective agents against such injuries (Huniqiguli et al., 2017).

Propolis flavonoids possess multiple functions, including antibacterial, antiviral, antioxidant, antitumor, cardiovascular protection, hypoglycemic, and tissue-protective activities, making them a growing focus of research in functional foods and natural medicine.

It is worth noting that the composition and content of flavonoids in propolis vary significantly depending on geographic origin, season, and botanical source. This diversity is both the charm of natural products and a challenge for standardization. Only through precise qualitative and quantitative analyses can the pharmacological value of propolis flavonoids be evaluated more clearly and reliably.

References

[1] Benguedouar L, Lahouel M, Gangloff S C, et al. Ethanolic extract of Algerian propolis and galangin decreased murine melanoma tumour progression[J]. Anti-Cancer Agents in Medicinal Chemistry, 2016, 16(10): 1172-1183.
[2] Bertram J.F. Hudson, Joseph I. Lewis. Polyhydroxy flavonoid antioxidants for edible oils: structural criteria for activity[J]. Food Chemistry, 1983, 10(2): 111-120.
[3] Chen C N, Wu C L, Shy H S, et al. Cytotoxic prenylflavanones from Taiwanese propolis[J]. Journal of Natural Products, 2003, 66(4): 503-506.
[4] Torjussen J, Bahr R. Injuries among competitive snowboarders at the national elite level[J]. American Journal of Sports Medicine, 2005, 33(3): 370-377. (Note: This reference seems unrelated to propolis; please verify.)
[5] Fang Z. Propolis – A treasury of flavonoid compounds[J]. Journal of Bee, 1998(9): 11-12. (in Chinese)
[6] Huniqiguli A, Ayinuer Y, Mayinuer D, et al. Research progress on pharmacological effects of flavonoid compounds in propolis[J]. Advances in Biotechnology, 2017, 7(1): 13-19. (in Chinese)
[7] Lü Z T, Jiang D Y. Experiment and application of propolis flavonoids in inhibiting tumors[J]. Journal of Bee, 1999(3): 8-10. (in Chinese)
[8] Peng Y M, Pan Y. Effects of propolis flavonoids supplementation on myocardial energy metabolism enzymes in overtraining mice[J]. Journal of Wuhan Institute of Physical Education, 2010, 44(8): 36-38. (in Chinese)
[9] Wang G Y, Shen M S, Zhang J, et al. Effects of propolis flavonoids on bcl-2 and bax gene mRNA expression in thymus of aging mice[J]. Journal of Mudanjiang Medical University, 2010, 31(4): 9-10. (in Chinese)
[10] Xu Y, Lei M J, Cheng C. Propolis and propolis flavonoids[J]. Food Industry, 2005(3): 17-20. (in Chinese)
[11] Yang M, Sui D J, Chen W X, et al. Study on hypoglycemic mechanism of total propolis flavonoids in STZ-induced diabetic rats[J]. Journal of Chinese Medicinal Materials, 2014, 37(9): 1623-1626. (in Chinese)
[12] Yang M, Sui D J, Chen W X, et al. Hypoglycemic effect of total propolis flavonoids on alloxan-induced diabetic rats[J]. Chinese Pharmaceutical Journal, 2014, 49(16): 1410-1413. (in Chinese)
[13] Yang M, Sui D J, Chen W X, et al. Effects of total propolis flavonoids on glycolipid metabolism and antioxidant activity in spontaneously diabetic rats[J]. Chinese Pharmaceutical Journal, 2015, 50(3): 217-220. (in Chinese)
[14] Yuan L J, Zhao L, Zhang Y, et al. Protective effect of propolis flavonoids on cerebral ischemia-reperfusion injury in rats[J]. Chinese Journal of Gerontology, 2010, 30(15): 2187-2188. (in Chinese)
[15] Zhang C P, Hu F L. Flavonoids in propolis[J]. Natural Product Research and Development, 2009, 21(6): 1084-1090. (in Chinese)
[16] Zhang Y C, Liu S, Wang C T. Health functions and application prospects of propolis flavonoids[J]. Gansu Animal Husbandry and Veterinary, 2017(6): 22-23. (in Chinese)