In-vitro Analysis of Trypsin and Alpha - Amylase Inhibitory Activities in Selected Legume Varieties in Sri Lanka

Aim: To quantify the Trypsin Inhibitory Activity (TIA) and Alpha - Amylase Inhibitory Activity (AIA) in legume varieties with effect of cooking.

Study Design: Seeds of twelve legume varieties grown in Complete Randomized Block Design (CRBD) in experimental field conditions were used and data analysis was performed using one-way ANOVA at 95% confidence interval using MINITAB statistical software.

Place and Duration of Study: Grain Legumes and Oil Crops Research and Development Centre (GLOCRDC), Angunakolapalessa and Industrial Technology Institute (ITI), Colombo, Sri Lanka between June 2019 and Dec 2019.

Methods: Ethanolic (80%) extracts of raw and cooked grain legumes were used. In determining TIA, N-α-benzoyl-DL-arginine-p-nitroanilide hydrochloride (BAPA) is used as a synthetic substrate for trypsin enzyme and the rate of hydrolysis was measured by intensity of colour released by p-nitroaniline. AIA was carried out determining the maltose content which was released by hydrolysis of starch in the presence of amylase enzyme using reduction of 3, 5-dinitrosalicylic acid.

Results: TIA in raw legumes ranged from 0.65±0.02 mg/g (ANK- Brown) to 1.52±0.01 mg/g (ANKCP1) while in cooked legumes ranged from -0.11±0.1 mg/g (ANK-Black) to 0.61±0.02 mg/g (MI 5). In pressure cooking (120oC, 10 min) considerable reduction in TIA of 53.74% (MI6) to 100% (ANK-Black, Bombay) was observed. A significant difference (p<0.05) in TIA among the varieties as well as among cooked form of varieties were observed (one- way ANOVA). Further a significant difference (p<0.05) in TIA was observed between cooked and raw form in each legume variety (Paired T-Test).

AIA of cooked samples was ranged from - 11.61% (MI 6) - 23.05% (MISB1) and there was no significant difference (p<0.05) in AIA among the most of the legume varieties.

Conclusion: A significant reduction of TIA among the legumes varieties was observed in the pressure cooking process while a significant activity of alpha- amylase was not seen in cooked legumes.