Corn silk (Zea mays L.), a source of natural antioxidants with α-amylase, α-glucosidase, advanced glycation and diabetic nephropathy inhibitory activities.

The oxidative stress plays a critical role in the progression of diabetes mellitus (DM) and its complications. Corn silk is a traditional medicine used to treat DM. The aim of this study is to investigate the antioxidant capacity of corn silk, as well as its inhibitory potential on DM and diabetic nephropathy (DN). The ethanol extract of corn silk (CS) was liquid-liquid fractionated to get petroleum ether fraction (PCS), ethyl acetate fraction (ECS), n-butanol fraction (BCS) and water fraction (WCS). The Folin-Ciocalteu and AlCl3 assay showed that silk corn contained considerable amount of phenolics and flavonoids, ECS and BCS were the two phenolic-enriched fractions with highest TPC and TFC values. The ECS and BCS showed the highest total antioxidant activity and reducing power, as well as the strongest scavenging activity against DPPH and hydroxyl radicals, compared to CS and other fractions. The ECS and BCS displayed appreciable anti-hyperglycaemic effect indicated by the significant inhibition on α-amylase and α-glucosidase in enzymatic assays. In BSA-glucose model, ECS and BCS effectively inhibited the formation of advanced glycation end products (AGEs). In addition, the anti-diabetic nephropathy activity assay displayed that CS, ECS and BCS significantly inhibited the production of Col IV, FN and IL-6 in high-glucose stimulated mesangial cells at 200 μg/mL. These findings suggested the antioxidant activities of corn silk could contribute, at least in part, to its traditionally claimed therapeutic benefits on DM and DN. The phenolic-enriched CS fractions could be considered as a source of natural antioxidants and further developed for the prevention and treatment of DM and its complications including DN.

Wang KJ ，Zhao JL 《-》

Annona muricata Linn. leaf as a source of antioxidant compounds with in vitro antidiabetic and inhibitory potential against α-amylase, α-glucosidase, lipase, non-enzymatic glycation and lipid peroxidation.

Annona muricata leaves are used in traditional medicine to manage diabetes mellitus and its complications. The aim of this study was to evaluate the potential in vitro antidiabetic properties of Annona muricata leaf by identifying its main phytochemical constituents and characterizing the phenolic-enriched fractions for their in vitro antioxidant capacity and inhibitory activities against glycoside and lipid hydrolases, advanced glycation end-product formation and lipid peroxidation. Ethanol extract of A. muricata leaf was subjected to a liquid-liquid partitioning and its fractions were used in enzymatic assays to evaluate their inhibitory potential against α-amylase, α-glucosidase and lipase, as well as their antioxidant (DPPH, ORAC, FRAP and Fe2+-ascorbate-induced lipid peroxidation assays) and anti-glycation (BSA-fructose, BSA-methylglyoxal and arginine-methylglyoxal models) capacities. In addition, identification of the main bioactive compounds of A. muricata leaf by HPLC-ESI-MS/MS analysis was carried out. Ethyl acetate (EtOAc) and n-butanol (BuOH) fractions showed, respectively, antioxidant properties (ORAC 3964 ± 53 and 2707 ± 519 μmol trolox eq g-1, FRAP 705 ± 35 and 289 ± 18 μmol trolox eq g-1, and DPPH IC50 4.3 ± 0.7 and 9.3 ± 0.8 μg mL-1) and capacity to reduce liver lipid peroxidation (p < .01). Also, EtOAc and BuOH, respectively, inhibited glycation in BSA-fructose (IC50 45.7 ± 13.5 and 61.9 ± 18.2 μg mL-1), BSA-methylglyoxal (IC50 166.1 ± 21.6 and 413.2 ± 49.5 μg mL-1) and arginine-methylglyoxal (IC50 437.9 ± 89.0 and 1191.0 ± 199.0 μg mL-1) assays, α-amylase (IC50 9.2 ± 2.3 and 6.1 ± 1.6 μg mL-1), α-glucosidase (IC50 413.1 ± 121.1 and 817.4 ± 87.9 μg mL-1) and lipase (IC50 74.2 ± 30.1 and 120.3 ± 50.5 μg.mL-1), and presented lower cytotoxicity, when compared to the other fractions and crude extract. Various biomolecules known as potent antioxidants were identified in these fractions, such as chlorogenic and caffeic acids, procyanidins B2 and C1, (epi)catechin, quercetin, quercetin-hexosides and kaempferol. This study presents new biological activities not yet described for A. muricata, which contributes to the understanding of the potential effectiveness in the use of the A. muricata leaf, especially its polyphenols-enriched fractions, for the management of diabetes mellitus and its complications.

Justino AB ，Miranda NC ，Franco RR ，Martins MM ，Silva NMD ，Espindola FS ... -  《-》

Kinetics of α-amylase and α-glucosidase inhibitory potential of Zea mays Linnaeus (Poaceae), Stigma maydis aqueous extract: An in vitro assessment.

Corn silk (Zea mays L., Stigma maydis) is an important herb used traditionally in many parts of the world to treat array of diseases including diabetes mellitus. Inhibitors of α-amylase and α-glucosidase offer an effective strategy to modulate levels of post prandial hyperglycaemia via control of starch metabolism. This study evaluated α-amylase and α-glucosidase inhibitory potentials of corn silk aqueous extract. Active principles and antioxidant attributes of the extract were also analysed. The α-amylase inhibitory potential of the extract was investigated by reacting its different concentrations with α-amylase and starch solution, while α-glucosidase inhibition was determined by pre-incubating α-glucosidase with different concentrations of the extract followed by addition of p-nitrophenylglucopyranoside. The mode(s) of inhibition of the enzymes were determined using Lineweaver-Burke plot. In vitro analysis of the extract showed that it exhibited potent and moderate inhibitory potential against α-amylase and α-glucosidase, respectively. The inhibition was concentration-dependent with respective half-maximal inhibitory concentration (IC50) values of 5.89 and 0.93mg/mL. Phytochemical analyses revealed the presence of alkaloids, flavonoids, phenols, saponins, tannins and phytosterols as probable inhibitory constituents. Furthermore, the extract remarkably scavenges reactive oxygen species like DPPH and nitric oxide radicals, elicited good reducing power and a significant metal chelating attributes. Overall, the non-competitive and uncompetitive mechanism of action of corn silk extract is due to its inhibitory effects on α-amylase and α-glucosidase, respectively. Consequently, this will reduce the rate of starch hydrolysis, enhance palliated glucose levels, and thus, lending credence to hypoglycaemic candidature of corn silk.

Sabiu S ，O'Neill FH ，Ashafa AOT 《-》

Inhibitory Effects of Siegesbeckia orientalis Extracts on Advanced Glycation End Product Formation and Key Enzymes Related to Metabolic Syndrome.

Hung WC ，Ling XH ，Chang CC ，Hsu HF ，Wang SW ，Lee YC ，Luo C ，Lee YT ，Houng JY ... -  《MOLECULES》

Antidiabetic effects of Syzygium cumini leaves: A non-hemolytic plant with potential against process of oxidation, glycation, inflammation and digestive enzymes catalysis.

Plant materials are commonly used in traditional medicine in order to treat various diseases such as Diabetes mellitus. Some plants, such as Syzygium cumini, have the capability to act controlling oxidative stress and protein glycation besides their potential to decrease hyperglycemia and hyperlipidemia by the inhibition of the catalysis of digestive enzymes. The aim of this study was to evaluate the antioxidant and antiglicant activity of S. cumini leaves fractions, their capacity to inhibit hydrolases and lipase enzymes, as well as the cytotoxicity effects against erythrocytes and comparate these results with isolate quercetin flavonoid. Ethnobotanical researches, carried out by academic studies at the Federal University of Uberlandia, led us to choose S. cumini as a potential plant for treatment of Diabetes mellitus. Fractions from ethanolic extract of S. cumini (hexane/Hex, dichloromethane/DCM, ethyl acetate/EtOAc, n-butanol/ButOH and water/H2O) were used to evaluate their antioxidant (DPPH, ORAC and FRAP) and antiglycant (BSA/fructose, BSA/methylglyoxal and Arginine/Methylglyoxal) activity as well as the inhibitory potential against α-amylase, α-glucosidase and lipase. In addition, identification of the main bioactive compounds of S. cuimini leaves by HPLC-ESIMS/MS analysis was carried out. Our results indicate that all fractions, for exception Hex, present noteworthy antioxidant activity, mainly in EtOAc and ButOH fractions (FRAP 1154.49 ± 67.37 and 1178.27 ± 21.26 μmol trolox eq g-1, respectively; ORAC 1224.63 ± 58.16 and 1313.53 ± 85.23 μmol trolox eq g-1, respectively; DPPH IC50 15.7 ± 2.4 and 23.5 ± 2.7 μg mL-1, respectively). Regarding the antiglycant activity (BSA/fructose and Arginine/Methylglyoxal models), all fraction, for exception Hex, presented inhibition higher than 85%. All fractions were capable to inhibit 100% of α-amylase and the fractions DCM, EtOAc and ButOH inhibited α-glucosidase more than 50%. Regarding the lipase assay, DCM and Hex had the best activity (31.5 ± 14.3 and 44.3 ± 4.5 μg mL-1, respectively). Various biomolecules known as potent antioxidants were identified in these fractions, such as quercetin, kaempferol, luteolin and (Epi)catechin. S. cumini fractions and quercetin presented promising antioxidant and antiglycation properties as well as the ability to inhibit digestive enzymes. This study presents new biological activities not yet described for S. cumini which provide new possibilities for further studies in order to assess the antidiabetic potential of S. cumini fractions especially EtOAc and ButOH.

Franco RR ，Ribeiro Zabisky LF ，Pires de Lima Júnior J ，Mota Alves VH ，Justino AB ，Saraiva AL ，Goulart LR ，Espindola FS ... -  《-》