Orthosiphon stamineus (Misai Kucing) for Diabetes: A Translational Reappraisal of Human Evidence, Dose, Mechanistic Assays and Safety

A 2022 systematic review concluded that Orthosiphon stamineus (misai kucing, Java tea) could be an antidiabetic agent, based on 31 studies that were almost entirely in vitro or in animals. This review examines their translation to people. No randomised trial of O. stamineus on glucose or HbA1c was found. The only human clinical data cited for diabetes came from multi-herb prescriptions, and the only placebo-controlled human trial identified found no diuretic effect. Converted by body surface area, the effective rat doses equal 4.8 to 19.4 g of extract a day for a 60 kg adult, 3 to 13 times the highest daily dose in the European Medicines Agency draft monograph; only the mouse studies were within or near that range. The α-glucosidase assays that showed extracts outperforming acarbose used an enzyme of unstated origin, against which acarbose was weak, as is typical of the yeast enzyme. Toxicity in animals was low, but lipophilic extracts and eupatorin inhibited CYP3A4 and CYP2D6, and the European monograph contraindicates use where fluid intake must be restricted, as in advanced kidney disease. O. stamineus should not be presented as an antidiabetic until standardised extracts at monograph doses are tested in randomised trials.