Combination effects of rice extract and five aromatic compounds against α-glucosidase, α-amylase and tyrosinase.

Rice is a source of bioactive compounds related to human health and has been used for both consumption and traditional medicine. The authors investigated the synergistic and additive effect of rice extract (RE) combined with five aromatic compounds against three enzymes: α-glucosidase, α-amylase and tyrosinase. RE was purified by thin-layer chromatography (TLC) and preparative TLC (PTLC) with different solvent systems. RE had higher α-glucosidase and α-amylase inhibitory activity than the five aromatic compounds, while the five aromatic compounds had higher tyrosinase inhibitory activity than RE. The combination of RE/acarbose produced synergic inhibition of α-glucosidase and α-amylase, whereas RE showed additive inhibition of both enzymes when combined with aromatic compounds. The five aromatic compounds showed additive inhibition of tyrosinase when combined with RE. The combination of 2-methoxy-4-vinylphenol/vanillin/guaiacol produced synergistic inhibition of α-amylase while showing antagonism of α-glucosidase and tyrosinase. Interestingly, the RE produced additive inhibition of α-glucosidase, α-amylase and tyrosinase when combined with the 2-methoxy-4-vinylphenol/vanillin/guaiacol combination. RE had rich bioactive compounds related to α-glucosidase, α-amylase and tyrosinase inhibitory activity. Volatile compounds, including 2-methoxy-4-vinylphenol, vanillin and guaiacol, enhanced the inhibitory activity of RE against α-glucosidase, α-amylase and tyrosinase activities.

Synthesis and inhibitory activity of N-acetylpyrrolidine derivatives on α-glucosidase and α-amylase.

BACKGROUND AND PURPOSE: Carbohydrate hydrolysis enzymes including α-glucosidase and α-amylase are related to type 2 diabetes mellitus. The inhibiting of these enzymes might use for type 2 diabetes mellitus treatment. EXPERIMENTAL APPROACH: N-substituted-acetylpyrrolidine linked with -benzyl- (N-(benzyl)-2-acetylpyrrolidine (4a)) and -tosyl- (N-(tosyl)-2-acetylpyrrolidine (4b)) were synthesized and evaluated for their pharmaceutical properties against α-glucosidase and α-amylase and free radical scavenging activity. The structures of 4a and 4b were determined through spectral studies (1H-NMR). FINDINGS / RESULTS: Both compounds 4a and 4b had highest inhibitory potential on α-glucosidase with the IC50 values of 0.52 ± 0.02 and 1.64 ± 0.08 mM, respectively. The kinetic investigation of 4a and 4b against α-glucosidase and α-amylase were functioned in mixed type inhibition. Moreover, both compounds are more likely to bind with the free enzyme than the enzyme-substrate complex based on the Ki < Ki´ on the α-glucosidase and α-amylase enzymes. Regarding the free radical scavenging, 4a had a higher capacity than 4b with IC50 values of 1.01 ± 0.010 mM for 4a and 1.82 ± 0.048 mM for 4b. CONCLUSION AND IMPLICATIONS: Our results indicated that a derivative of N-substitute-acetylpyrrolidine had high potential to inhibit α-glucosidase and α-amylase, and their free radical scavenging properties might be applied to the therapeutic care of patients with type 2 diabetes mellitus.

α-Glucosidase, α-amylase, and tyrosinase inhibitory potential of capsaicin and dihydrocapsaicin.

Chili is a spicy plant and is widely used in traditional medicine. Capsaicin and dihydrocapsaicin belong to the capsaicinoid group, which is produced from chili. This study aims to investigate the antidiabetic properties and anti-melanin synthesis of capsaicinoids by studying the inhibitory activity of capsaicin and dihydrocapsaicin with α-glucosidase, α-amylase, and tyrosinase. The results revealed that dihydrocapsaicin with IC50 had 4.13-fold and 3.00-fold for α-glucosidase and α-amylase, respectively, which are lower than capsaicin. Moreover, the IC50 of capsaicin with tyrosinase had 1.73 times less than dihydrocapsaicin. The inhibition constant (Ki ) also supported that the dihydrocapsaicin had higher inhibitory activity than capsaicin against α-glucosidase and α-amylase, but lower inhibitory activity than capsaicin on tyrosinase. Capsaicin and dihydrocapsaicin functioned in mixed-type inhibition on each enzyme, except that capsaicin functioned in competitive inhibition of tyrosinase. The results indicated that capsaicin and dihydrocapsaicin had more potent anti-melanin synthesis than antidiabetic properties. PRACTICAL APPLICATIONS: This study presents the inhibition potential of capsaicin and dihydrocapsaicin on antidiabetes and anti-melanin properties by standard methods for inhibitory activity against α-glucosidase, α-amylase, and tyrosinase. We suggest the application of these results in the development of antidiabetes and anti-melanin drugs for pharmaceutical and cosmetic industries.