Exploring the hypoglycemic potential of fresh, semangit, and bosok tempe: A comparative metabolite profile

Tempe, a traditional Indonesian fermented soybean product made with <i>Rhizopus</i> spp., is classified based on fermentation duration into fresh (two days), <i>semangit</i> (five days), and <i>bosok</i> (seven days) varieties, fermented at room temperature (28-30°C). Longer fermentation is believed to enhance its antidiabetic properties. The aim of this study was to compare the metabolite profiles and hypoglycemic activities of fresh, <i>semangit</i>, and <i>bosok</i> tempe made from germinated and non-germinated soybeans. Diabetic rat models were used to assess the effects of these tempe types on body weight, blood glucose levels, serum insulin, pancreatic β-cell count, and glycogen content in liver and muscle tissues. Metabolomic profiling was conducted using gas chromatography-mass spectrometry (GC-MS), followed by principal component analysis (PCA) to assess the influence of fermentation stage and germination. Fresh tempe, especially from germinated soybeans, had the highest moisture content. Fermentation duration significantly influenced color, texture, and pH, with <i>bosok</i> tempe showing the most notable changes. Tempe and gliclazide significantly reduced blood glucose in diabetic rats in vivo, with <i>semangit</i> and <i>bosok</i> tempe restoring levels close to normal. However, weight loss was not reversed. <i>Bosok</i> non-germinated tempe induced the highest insulin levels among tempe treatments and improved β-cell count and density to levels comparable with gliclazide. Glycogen stores in the liver and muscle were significantly restored by tempe, with <i>bosok</i> non-germinated tempe showing the greatest effect. GC-MS profiling identified 154 metabolites, of which 63 were annotated. Fermentation and germination shifted the metabolite profile, with <i>bosok</i> non-germinated tempe showing the highest diversity, including amino acids, sugars, and amines. PCA separated samples by fermentation stage, highlighting metabolite accumulation with prolonged fermentation. The findings revealed that <i>bosok</i> tempe from non-germinated soybeans had the highest abundance of bioactive metabolites, including isoflavones, which likely contributed to its superior antioxidant and hypoglycemic potential compared to other tempe types.