Bioactive Prenylated Flavonoids from Macaranga tanarius (L.) Müll.-Arg.: A Systematic Scoping Review of Phytochemistry, Antioxidant Activity, and Antidiabetic Mechanisms

Macaranga tanarius (L.) Müll.-Arg. (Euphorbiaceae), a botanical source of green-propolis, contains diverse secondary metabolites, including characteristic prenylated flavonoids. This systematic scoping review mapped phytochemical, antioxidant, preclinical antidiabetic, safety, and translational evidence using direct, comparative, and contextual evidence roles. Source verification yielded 49 records: 25 direct M. tanarius studies, 18 comparative Macaranga studies, and six contextual studies. Recurring prenylated flavonoids included macaflavanones A-G and nymphaeol/propolin-type compounds. Antioxidant evidence was most frequently reported but remained mainly chemical/in vitro; a methanolic leaf extract showed 2,2-diphenyl-1-picrylhydrazyl and 2,2ʹ-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) half-maximal inhibitory concentration values of 0.87 and 4.36 µg/mL. Antidiabetic evidence remained preclinical: Glucose uptake was associated with AMP-activated protein kinase phosphorylation and glucose transporter 1 (GLUT1) expression in L6 myotubes, with additional findings from animal models of diabetic nephropathy and retinopathy. These findings arise from different models and do not establish a single confirmed therapeutic mechanism. No human clinical study was identified, and safety evidence remains preliminary. M. tanarius therefore remains a preclinical natural-product candidate requiring botanical/chemical standardization, pharmacokinetic/exposure studies, repeated-dose safety assessment, and further animal-model validation before clinical investigation.