Effect of Ultrasound-Assisted Hot Water Extraction on Antioxidant and Enzyme Inhibitory Activities of Stink Bean (Parkia Speciosa) Pod Extract

Ku, Angie Xiao Qing (2026) Effect of Ultrasound-Assisted Hot Water Extraction on Antioxidant and Enzyme Inhibitory Activities of Stink Bean (Parkia Speciosa) Pod Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

The increasing demand for sustainable and functional food ingredients highlights the need to valorise underutilised agro-waste such as stink bean pods, yet conventional extraction methods remain inefficient in preserving and recovering heat-sensitive compounds responsible for their bioactive properties. This study aimed to investigate the effect of ultrasound-assisted hot water extraction (UAHWE) on the bioactive properties of stink bean pods extracts and to compare its performance with ultrasound extraction (UE) and hot water extraction (HWE). The effects of ultrasound amplitude (50%, 70%, and 90%) and hot water extraction time (15 and 30 min) on colour, pH, total phenolic content (TPC), total flavonoid content (TFC), antioxidant activities (DPPH, FRAP, ABTS), and enzyme inhibitory activity (anti-lipoxygenase, anti-LOX and α-amylase inhibitory activity, AAI) were evaluated. Results showed that all extraction methods significantly affected the measured parameters (p < 0.05). Increasing ultrasound amplitude and reducing hot water extraction time significantly (p < 0.05) increased bioactive properties of stink bean pods extracts. HWE resulted in the greatest colour change, whereas UE better reduced the change of colour. UAHWE significantly increased TPC from 59.65 to 85.72 mg GAE/g (p < 0.05), representing an approximate 43.7% improvement compared to standalone extraction methods. The optimal conditions identified at 90% ultrasound amplitude and 15 min extraction time contributing to the significantly (p < 0.05) highest TPC, FRAP, and ABTS among all extraction conditions. These findings demonstrate that UAHWE synergistically enhances extraction efficiency while preserving bioactivity, making it an effective and green technique for maximising the functional potential of stink bean pods extracts. Further studies on process optimisation and compound identification are recommended for industrial applications.