Abstract
Introduction: Lumnitzera littorea grown at CanGio Mangrove Forest has been investigated. The present study reports the isolation, characterization and evaluation of the alpha-glucosidase inhibitory activity of isolated compounds from Lumnitzera littorea leaves.
 Methods: Their structures were elucidated by spectroscopic methods (including MS, 1D and 2D–NMR) and comparison with values from the literature. From the n-hexane extract, nine compounds including lupeol (1), betulin (2), betulinic acid (3), oleanolic acid (4), corosolic acid (5), -sitosterol (6), beta-sitosterol 3-O- beta-D-glucopyranoside (7), stigmast-5-ene-3beta-O-(6-O-hexadecanoyl-beta-D-glucopyranoside) (8), and stigmast-4-ene-3-one (9) were isolated and identified.
 Results: The results of the alpha-glucosidase inhibitory activity showed thatcorosolic acid (5) and oleanolic acid (4) were the most potent, with IC50 values of 17.86 +/- 0.42 and 18.82 +/- 0.59 ug/mL, respectively. Five of the other seven compounds exhibited inhibitory activity with IC50 values below 100 ug/mL, and higher than the positive control acarbose (127.64 +/- 0.64 ug/mL).
Highlights
Lumnitzera littorea grown at CanGio Mangrove Forest has been investigated
One of the therapeutic approaches for decreasing blood glucose rise after a meal is to slow down the absorption of glucose by inhibition of carbohydrate hydrolyzing enzymes, such as α-glucosidase. α-Glucosidase is an intestinal enzyme that breaks down α-1,4 linked polysaccharides to α-glucose, which leads to the high blood sugar levels
Betulinic acid (3): white powder, ESI-MSm/z: 455.38 [M-H]− corresponding for C30H48O3. 1H-Carbon-13 nuclear magnetic resonance 1H NMR (NMR) (500 MHz, CDCl3) d: 4.74, 4.61, 3.19, 3.00 (m, H19), 1.69 (s, H-30), 0.98 (s, H-26), 0.96 (s, H-27), 0.93 (s, H-23), 0.82 (s, H-25) and 0.75 (s, H-24), 13C-NMR (125 MHz, CDCl3) d: 180.5 (C-28), 150.6 (C20), 109.8 (C-29), 79.2 (C-3), 56.5 (C-17), 55.5 (C-5), 50.7 (C-9), 49.4 (C-19), 47.1 (C-18), 42.6 (C-14), 40.9 (C-8), 39.0 (C-4), 38.9 (C-1), 38.6 (C-13), 37.4 (C-10), 37.2 (C-22), 34.5 (C-7), 32.3 (C-16), 30.7 (C-15), 29.9 (C-21), 28.1 (C-23), 27.6 (C-2), 25.7 (C-12), 21.0 (C11), 19.5 (C-30), 18.4 (C-6), 16.3 (C-26), 16.2 (C-25), 15.5 (C-24) and 14.9 (C-27)
Summary
The present study reports the isolation, characterization and evaluation of the α-glucosidase inhibitory activity of isolated compounds from Lumnitzera littorea leaves. Diabetes is a chronic disease associated with unusually high levels of glucose in the blood. The goal of diabete therapy is the maintenance of normal blood glucose levels after a meal. Α-Glucosidase is an intestinal enzyme that breaks down α-1,4 linked polysaccharides to α-glucose, which leads to the high blood sugar levels. Our published research showed that the αglucosidase inhibitory activity on all extracts and isolated flavonoids from the leaves of Lumnitzera littorea were very strong 2. The aim of this study was to isolate phytoconstituents and evaluate the inhibition of αglucosidase activity of the compounds isolated from the n-hexane extract of L. littorealeaves
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