GCMS profiling and in silico screening of alpha-amylase inhibitors in traditional pigmented rice varieties (Oryza sativa Linn) of Tamil Nadu

Alpha-amylase inhibitors are oral antidiabetic drugs known for inhibiting the alpha-amylase enzyme, which carries out starch hydrolysis, enabling its assimilation in the intestine. However, these drugs can cause several adverse side effects. The present study evaluated the alpha-amylase inhibitory potential of traditional pigmented rice bran crude extracts. This was accomplished through GC-MS profiling of the metabolites contained in the extracts and exploring their alpha-amylase inhibitory potential through molecular docking. Among the six tested pigmented rice brans, the Mapillai Samba extract showed the strongest alpha-amylase inhibition (IC50 = 12.81 mu g/ml), followed by Karuppu Kavuni, Elupaipoo Samba, Karuthakar, Kattuyanum, Kodavazhai, and the commercial variety White Ponni (IC50 = 20.90, 27.91, 35.71, 37.02, 45.58, and 48.18 mu g/ml, respectively). The standard inhibitor, acarbose, had an IC50 value of 13.52 mu g/ml. Metabolite profiling of seven rice varieties identified 127 compounds. The in-silico study screened the ability of the compounds to inhibit human pancreatic alpha-amylase (ID:1B2Y). Eight compounds, namely, tricycle [20.8.0.0 (7,16)]triacontane, 1(22),7(16)-diepoxy-; beta-D-glucopyranoside, methyl; stigmast-5-en-3-ol, (3. beta,24s)-; campesterol; stigmasta-5,20 (22)-dien-3-O; lup-20 (29)-ene-3,21,28-triol, 28-acetate; (3. beta,21. beta.)-; and (-)-vincadifformine were identified from the traditional rice varieties. Cholesterol was also identified (which was distinctive to White Ponni). These compounds had binding energies ranging from -8.26 to -9.98 kcal/mol, indicating them as ligands with stronger affinity to the active site of 1B2Y compared to acarbose (-11.08 kcal/mol). To test the alpha-amylase inhibitory activity of the high-affinity compounds, the synthetic stigmast-5-en-3-ol, (3. beta,24s)- was assayed and was found to exhibit an IC50 of 13.59 mu g/ml. The findings of this study indicate that the metabolites in pigmented rice brans may function independently or synergistically to inhibit alpha-amylase.

Automated summary

The traditional pigmented rice bran extracts were found to inhibit the activity of alpha-amylase, with Mapillai Samba extract showing the strongest inhibitory effect. This study identified eight compounds from the rice varieties that had a higher binding affinity to the active site of 1B2Y compared to the standard inhibitor acarbose.