Eugenia biflora Tea lowers blood sugar in diabetics but prolonged use tied to toxicity

A group of Myrtaceae species, popularly known as "Pedra-ume-caá" in the Brazilian Amazon, are commonly used for the treatment of diabetes. Eugenia biflora leaves are sold in street markets and traditionally used by Amazonian peoples in the form of tea to control diabetes, diarrhoea, intestinal inflammation and bleeding. Despite its use in folk medicine, chemical and pharmacological studies with this species are still scarce. Therefore, Dr Marcos B. Machado and his team conducted a study to identify the chemical constituents and evaluate the hypoglycemic and toxic effects of the dry extract of the E. biflora leaves (DEEB).

In this study, the researchers analysed DEEB, obtained by infusion, using LC-HRMS and NMR, whose catechin flavonoid was quantified using NMR. They evaluated the antidiabetic effect of DEEB according to its inhibition of the enzymes α-amylase and α-glucosidase, as well as the content of total phenols, free radical scavenging and antiglycation activities, and its in vitro cell viability. They also performed oral maltose tolerance and chronic multiple-dose tests (28 days) in streptozotocin-induced diabetic mice (STZ). They further evaluated the hypoglycemic effect and toxicity of this extract in the multiple-dose assay. They evaluated biochemical parameters, hemolysis, and levels of the thiobarbituric acid reactive species in the liver and performed histopathological analyses of the kidneys and liver.

Key findings of the study:

• Upon analysis, the researchers identified eight phenolic compounds, with catechin (15.5 ± 1.7 mg g−1) being the majority compound and a possible chemical marker of DEEB.
• They found that the extract showed inhibition activity of the enzyme α-glucosidase.
• They noted that the chronic administration of DEEB (50 mg/kg of body weight) reduced glucose levels in diabetic animals, similar to acarbose.
• However, they also noted that the DEEB (100 and 200 mg/kg bw) caused the premature death of mice by D22 of the treatment.
• They reported that one of the mechanisms of toxicity in DEEB may be related to the aggravation of oxidative stress in the liver.
• Upon histopathological study, they found that DEEB failed to minimize the progression of the toxicity of diabetes caused by STZ.

The authors concluded, "This study demonstrated the hypoglycemic potential of E. biflora leaves. However, the prolonged use of this tea can be harmful to its users due to its considerable toxicity, which needs to be better investigated."

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DOI: https://doi.org/10.1016/j.jep.2022.115276