Piper nigrum and Morinda lucida Possess Antioxidant Capacities and Regulate the Activities of Key Carbohydrate and Lipid Digestive Enzymes

Introduction: Carbohydrate and lipid digestive enzymes are instrumental in the absorbability of nutrients associated to diabetes and obesity. This study evaluated hydroethanolic extracts of Piper nigrum leaf and Morinda lucida stem bark for antioxidant capacity and enzymes (carbohydrate and lipid digestive) inhibition.

Methods: Colorimetric assays determined enzyme (α-amylase, α-glucosidase, lipase and cholesterol esterase) inhibition and antioxidant capacity (total phenolic (TPC) and flavonoid (TFC) content, radical scavenging activity (DPPH, ABTS), and ferric reducing antioxidant power (FRAP)) of hydroethanolic ethanolic extracts, ethyl acetate and hexane fractions.

Results: At 1 mg/ml extracts of P nigrum and M lucida inhibited α- amylase (9.82±1.05 - 36.63±0.69 %) and α-glucosidase (22.47±0.34 - 67.77±0.58 %) activities. At 100 µg/ml extracts and fractions inhibited lipase (56.72±1.11 - 81.61±0.71 %) and cholesterol esterase (18.14 ±0.79 - 36.84±0.70 %) activities. IC50 for α- amylase (2.20±0.02 - 7.8±1.42 mg/ml), α-glucosidase (0.16±0.01 - 3.74±0.01 mg/ml), lipase (8.58±2.57 - 53.03±5.20 µg/ml) and cholesterol esterase (172.20±5.12 - 419.80±4.55 µg/ml) were registered. At 4 mg/ml, P. nigrum presented a higher TPC (153.78±8.31 - 354.63±6.33 mg/ml), TFC (21.65±1.14 -33.86±0.00 mg/ml) than M lucida TPC (10.21±0.11 - 169.89±6.54 mg/ml), TFC (ND - 87.32±6.14 mg/ml). P nigrum presented radical scavenging (DPPH and ABTS) activity with IC50 0.12±0.00 - 1.27±0.01 mg/ml compared to 1.31±0.02 - 3.44±0.12 mg/ml of M lucida. The FRAP IC50 values were better for P nigrum (3.38±0.14- 4.48±1.05 mg/ml) than M lucida (3.34±1.32 - 15.4±2.03 mg/ml).

Conclusion: P nigrum presented better antioxidant capacity and more effective on lipid digestive enzymes while M lucida was more effective on carbohydrate digestive enzymes.