Phenolic Composition Profile and Antidiabetic Activities of Jack Bean Canavalia ensiformis (L.) DC. Tempeh

This study examined the effects of fermentation with Rhizopus oligosporus on cell wall structure and permeability, phenolic compound bioavailability, and antidiabetic potential of jack bean Canavalia ensiformis (L.) DC. tempeh. Fermentation significantly increased the total phenolic ( 21%) and flavonoid ( 152%) contents, mainly through the release of bound phenolics. Confocal fluorescence scanning microscopy with calcofluor white staining and fluorescein isothiocyanate-dextran probe permeation revealed the disruption of cellulose linkages in jack bean tempeh, which increased permeability and facilitated the diffusion of larger molecules. LC-ESI-QTOF-MS/MS identified 102 compounds across the free, conjugated, and bound phenolic fractions, with the conjugated fraction showing the most diverse composition. Certain bioactive compounds, such as D-(+)-3-phenyllactic acid, apigenin-7-O-glucoside, luteolin-7-neohesperidoside, kaempferol, arbutin, and oleacein, were tentatively linked to α-amylase and α-glucosidase inhibition. The free phenolic fraction exhibited the strongest α-amylase inhibition half maximal inhibitory concentration (IC_₅₀)=35.75±0.91 µg/mL, whereas the conjugated and bound fractions were most effective against α-glucosidase (IC_₅₀=353.70±119.79 and 56.33±10.40 µg/mL, respectively). Correlation analysis revealed positive associations between phenolic content and α-amylase inhibition (r>0.8, P<0.05). In summary, fermentation improved cell wall permeability, the release of bound phenolics, and antidiabetic potential, suggesting that jack bean tempeh, rich in bioaccessible phenolics, is a potential functional food for glycemic regulation. © 2026 The Korean Society of Food Science and Nutrition. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.