Bioassay-guided fractionation and identification of α-amylase inhibitors from Syzygium cumini leaves

Abstract

Context: Pancreatic α-amylase and α-glucosidase inhibitors serve as important strategies in the management of blood glucose. Even though Syzygium cumini (L.) Skeels (Myrtaceae) (SC) is used extensively to treat diabetes; scientific evidence on antidiabetic effects of SC leaves is scarce. Objective: SC leaf extract was investigated for α-amylase inhibitory effect and continued with isolation and identification of α-amylase inhibitors. Materials and methods: Bioassay-guided fractionation was conducted using in vitro α-amylase inhibitory assay (with 20–1000 μg/mL test material) to isolate the inhibitory compounds from ethyl acetate extract of SC leaves. Structures of the isolated inhibitory compounds were elucidated using 1H NMR and 13C NMR spectroscopic analysis and direct TLC and HPLC comparison with authentic samples. Study period was from October 2013 to October 2015. Results: An active fraction obtained with chromatographic separation of the extract inhibited porcine pancreatic α-amylase with an IC50 of 39.9 μg/mL. Furthermore, it showed a strong inhibition on α-glucosidase with an IC50 of 28.2 μg/mL. The active fraction was determined to be a 3:1 mixture of ursolic acid and oleanolic acid. Pure ursolic acid and oleanolic acid showed IC50 values of 6.7 and 57.4 μg/mL, respectively, against α-amylase and 3.1 and 44.1 μg/mL respectively, against α-glucosidase. Discussion and conclusions: The present study revealed strong α-amylase and α-glucosidase inhibitory effects of ursolic acid and oleanolic acid isolated from SC leaves for the first time validating the use of SC leaves in antidiabetic therapy.

In vitro antiglycation and hypoglycaemic effects of Syzygium cumini leaf extracts

“…Hence the respective inhibitors may have the ability to retard the catalysis by binding to the free enzyme as well as to the enzymesubstrate complex. In agreement with the previous findings of Poongunran et al (2016), higher inhibitory effects were observed with methanol and water extracts as the V max values obtained were lower and the K m values were higher when compared with those of ethyl acetate extracts.…”

“…However, kinetics of these inhibitory effects were not studied previously. Results on amylase inhibitory effects of the present study were in agreement with the results of Poongunran et al (2016). Lineweaver-Burk plots were produced with the data obtained in the presence of ethyl acetate ( Figure 6A), methanol ( Figure 6B) and water ( Figure 6C) mixed type inhibitory effects on α-amylase by the three extracts as K m and V max differed from those of the control sample [in the absence of inhibitory effects (0)].…”

Dietary ursolic acid improves health span and life span in male Drosophila melanogaster

“…C) in UA‐administered flies compared to controls, improving the energy resources and hence the climbing ability of aged male w 1118 flies. Although UA exhibits inhibitory effects on porcine α‐amylase and yeast α‐glucosidase activity in vitro glucose levels were not lowered but enhanced by UA intake in male fruit flies, indicating srl ‐mediated glucose upregulation by UA.…”

Identification of Bioactive Compounds and Analysis of Inhibitory Potential of the Digestive Enzymes fromSyzygiumsp. Extracts

“…e authors suggested a possible relationship between amylase inhibition and the presence of phenolic compounds. Poongunran et al [28], working with dried leaves of Syzygium cumini, found that extracts of methanol and water had high α-amylase inhibitory activity (98.3 ± 2.3 and 98.6 ± 1.6, respectively). e authors reported that the strong inhibition of the enzyme is due to the presence of oleanolic acid and ursolic acid, isolated from the leaves of Syzygium.…”

“…In addition to luteolin, Karthic et al [39] and Poongunran et al [28] describe in their studies the presence of other α-amylase and α-glycosidase inhibitors in seeds and leaves of Syzygium cumini, respectively. ey are betulinic acid, ursolic acid, and oleanolic acid, all with molecular weight of 456.7 g/mol.…”