Investigating the Effect of Fermentation Using Different Probiotics on Chemical Properties, Anti-Diabetic, and Anti-Inflammatory Properties of Guava Leaf Extracts

Chuah, Xin Yue (2025) Investigating the Effect of Fermentation Using Different Probiotics on Chemical Properties, Anti-Diabetic, and Anti-Inflammatory Properties of Guava Leaf Extracts. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Guava leaf is rich in polyphenolic compounds which are known for their antidiabetic and anti-inflammatory properties. This study aimed to determine the effects of different probiotic strains on antidiabetic activity and anti-inflammatory properties through fermentation of guava leaf extract (GLE) and to correlate viable cell counts, total phenolic content (TPC), and total flavonoid content (TFC) with bioactivities of fermented GLE. Lactobacillus acidophilus LA5 (L. acidophilus), Lactiplantibacillus plantarum TAR4 (L. plantarum), and Lacticaseibacillus casei ATCC393 (L. casei) —were used to ferment GLE at various concentrations, where 10% (v/v), 25% (v/v), and 50% (v/v) refer to the concentration of GLE. The samples were analyzed for viable cell counts, α-amylase inhibition activity, albumin denaturation inhibition activity, TPC and TFC. The results showed that L. casei fermented GLE at 50% (v/v) had the highest albumin denaturation inhibition (47.32± 0.05%, p<0.05), while the activity decreased at lower concentrations. L. casei fermented GLE at 10% (v/v) showed the highest α-amylase inhibition activity (99.67 ± 0.04%, p <0.05), which decreased at higher concentrations. L. plantarum and L. casei exhibited strong positive correlations between TPC and TFC with albumin denaturation inhibition activity, (r=0.790 and 0.821 for L. plantarum, and 0.815 and 0.828 for L. casei, respectively (p<0.05). For L. acidophilus, viable cell count exhibited strong negative correlation in inhibition activity of α-amylase (r=-0.866) (p<0.05). In conclusion, L. casei fermented GLE at 10% (v/v) showed the highest inhibition activity of α-amylase while at 50% (v/v) showed the highest inhibition activity of egg albumin. A future study is proposed to investigate the bioactivity of GLE in probiotic fermentation for 72 hours. Keywords: Guava leaf; Anti-diabetic activity; Anti-inflammatory activity; Probiotic fermentation