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 -amylase and -glucosidase inhibition.The free phenolic fraction exhibited the strongest -amylase inhibition [half maximal inhibitory concentration (IC50)=35.750.91 g/mL], whereas the conjugated and bound fractions were most effective against -glucosidase (IC50=353.70119.79 and 56.3310.40g/mL, respectively).Correlation analysis revealed positive associations between phenolic content and -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.