In vitro study on antidiabetic and antihypertensive activities of ethanolic extract of propolis of Indonesian stingless bee Tetragonula sapiens

The stingless bee, Tetragonula sapiens, is one of the species producing propolis in Indonesia. To date, there is still limited information about the standard characteristics and biological activity of propolis. This study investigated the standardized extract of Indonesian propolis in terms of its potency for controlling diabetes and high blood pressure in vitro, in accordance with its standard parameters. Three types of extracts; i.e., ethanolic extract of propolis (EEP), spray-dry propolis without wax (SDPNW), and spray-dry propolis with wax (SDPW); were prepared from T. sapiens stingless bees collected in South Sulawesi, Indonesia. The ethanolic extractable, loss on drying, ash, and water content parameters of EEP, SDPNW, and SDPW met the natural extract requirement. There is no significant value for their residual solvent levels (<0.54%), heavy metals (the absence of As, Cd, Pb, and Hg contamination), or the absence of microbial contamination. ACE inhibition activity on captopril, EEP, SDPNW, and SDPW had IC₅₀ values of 5.97, 115.06, 112.93, and 116.70 ppm, respectively. While the IC₅₀ values of acarbose, SDPNW, EEP, and SDPW for antidiabetic activity of α-glucosidase inhibition were 53.34, 56.48, 60.09, and 68.28 ppm, respectively. The TFC and TPC content of SDPNW were higher than EEP and SDPW, with values of 1.59% and 1.93%, respectively. It can be said that Indonesian propolis extract meets the standards for an extract and has the potential to reduce diabetic and hypertensive diseases. Further preclinical and clinical studies are needed to develop standardized propolis extract as an anti-diabetic and antihypertensive agent.