BackgroundThe aim of this paper is to evaluate the efficacy and safety of DLBS3233, a novel bioactive fraction derived from Cinnamomum burmanii and Lagerstroemia speciosa, in improving insulin resistance and preserving β-cell performance in patients with impaired glucose tolerance (IGT).Patients and methodsEighty adult subjects with IGT, defined as 2-hour postprandial glucose level of 140–199 mg/dL, were enrolled in this two-arm, 12-week, double-blind, randomized, placebo-controlled preliminary study. Eligible subjects were randomly allocated to receive either DLBS3233 at a dose of 50–100 mg daily or placebo for 12 weeks. The study mainly assessed the improvement of homeostatic model-assessed insulin resistance (HOMA-IR), the 15-minute and 2-hour plasma insulin levels, and the oral disposition index.ResultsAfter 12 weeks, DLBS3233 improved insulin resistance better than placebo as reflected by a reduced HOMA-IR (−27.04%±29.41% vs −4.90%±41.27%, P=0.013). The improvement of the first- and second-phase insulin secretion was consistently greater in DLBS3233 group than placebo group (−144.78±194.06 vs −71.21±157.19, P=0.022, and −455.03±487.56 vs −269.49±467.77, P=0.033, respectively). Further, DLBS3233 also significantly better improved oral disposition index than placebo. No serious hypoglycemia, edema, or cardiovascular-related adverse events were found in either groups.ConclusionThis study has shown that DLBS3233 at the dose of 50–100 mg once daily was well tolerated, and promisingly efficacious in improving insulin sensitivity as well as preserving β-cell performance in subjects with IGT.