ABSTRACT
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 (?-amylase, ?-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 ?- amylase (9.82±1.05 - 36.63±0.69 %) and ?-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 ?- amylase (2.20±0.02 - 7.8±1.42 mg/ml), ?-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.
ABSTRACT
Background: Astaxanthin from natural sources is typically esterified with fatty acids; hence, it must be hydrolyzed to remove esters before identification and quantification by conventional HPLC. Alkaline-catalyzed saponification and enzyme-catalyzed enzymolysis are the most commonly used de-esterification methods. However, information on the efficiency and isomerization during de-esterification of natural astaxanthin esters by these two methods remains scarce. Therefore, we conducted two HPLC-based experiments to determine which method is better for hydrolyzing astaxanthin esters. Results: To assess the effect of enzymolysis (0.67 U/mL cholesterol esterase, at 37°C) and saponification (0.021 M NaOH, at 5°C) conditions on free astaxanthin recovery and destruction or structural transformation of astaxanthin, we varied the total treatment time across a range of 195 min. The results showed that enzymolysis and saponification were complete in 60 min and 90 min, respectively. After complete hydrolysis, the maximum free astaxanthin recovery obtained by enzymolysis was 42.6% more than that obtained by saponification. The identification of by-products, semi-astacene and astacene, during the process of saponification also indicated that a more severe degradation of astaxanthin occurred during saponification. Moreover, the composition of astaxanthin isomers during saponification was similar to that of the isomers during enzymolysis between 30 min and 75 min (all-trans:9-cis:13-cis = 21:3:1, approximately) but dramatically changed after 90 min, whereas the composition in the enzymolysis treatment remained relatively stable throughout. Conclusion: Compared with saponification, enzymolysis with cholesterol esterase was recommended as a more accurate method for de-esterification of natural astaxanthin esters for further qualitative and quantitative HPLC analysis.