Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies

Fourteen triterpene acids, viz., three tirucallane-type (<b>1</b>–<b>3</b>), eight ursane-type (<b>4</b>–<b>11</b>), two oleanane-type (<b>12</b>, <b>13</b>) and one lupane type (<b>21</b>), along with boswellic alde...

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Main Authors: Najeeb Ur Rehman, Sobia Ahsan Halim, Mohammed Al-Azri, Majid Khan, Ajmal Khan, Kashif Rafiq, Ahmed Al-Rawahi, Rene Csuk, Ahmed Al-Harrasi
Format: Article
Language:English
Published: MDPI AG 2020-05-01
Series:Biomolecules
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Online Access:https://www.mdpi.com/2218-273X/10/5/751
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author Najeeb Ur Rehman
Sobia Ahsan Halim
Mohammed Al-Azri
Majid Khan
Ajmal Khan
Kashif Rafiq
Ahmed Al-Rawahi
Rene Csuk
Ahmed Al-Harrasi
author_facet Najeeb Ur Rehman
Sobia Ahsan Halim
Mohammed Al-Azri
Majid Khan
Ajmal Khan
Kashif Rafiq
Ahmed Al-Rawahi
Rene Csuk
Ahmed Al-Harrasi
author_sort Najeeb Ur Rehman
collection DOAJ
description Fourteen triterpene acids, viz., three tirucallane-type (<b>1</b>–<b>3</b>), eight ursane-type (<b>4</b>–<b>11</b>), two oleanane-type (<b>12</b>, <b>13</b>) and one lupane type (<b>21</b>), along with boswellic aldehyde (<b>14</b>), α-amyrine (<b>15</b>), epi-amyrine (<b>16</b>), straight chain acid (<b>17</b>), sesquiterpene (<b>19</b>) and two cembrane-type diterpenes (<b>18</b>, <b>20</b>) were isolated, first time, from the methanol extract of <i>Boswellia elongata</i> resin. Compound (<b>1</b>) was isolated for first time as a natural product, while the remaining compounds (<b>2</b>‒<b>21</b>) were reported for first time from <i>B. elongata.</i> The structures of all compounds were confirmed by advanced spectroscopic techniques including mass spectrometry and also by comparison with the reported literature. Eight compounds (<b>1</b>–<b>5, 11, 19</b> and <b>20</b>) were further screened for in vitro α-glucosidase inhibitory activity. Compounds <b>3</b>–<b>5</b> and <b>11</b> showed significant activity against α-glucosidase with IC<sub>50</sub> values ranging from 9.9–56.8 μM. Compound <b>4</b> (IC<sub>50</sub> = 9.9 ± 0.48 μM) demonstrated higher inhibition followed by <b>11</b> (IC<sub>50</sub> = 14.9 ± 1.31 μM), <b>5</b> (IC<sub>50</sub> = 20.9 ± 0.05 μM) and <b>3</b> (IC<sub>50</sub> = 56.8 ± 1.30 μM), indicating that carboxylic acid play a key role in α-glucosidase inhibition. Kinetics studies on the active compounds <b>3</b>–<b>5</b> and <b>11</b> were carried out to investigate their mechanism (mode of inhibition and dissociation constants <i>K<sub>i</sub></i>). All compounds were found to be non-competitive inhibitors with <i>K<sub>i</sub></i> values in the range of 7.05 ± 0.17–51.15 ± 0.25 µM. Moreover, in silico docking was performed to search the allosteric hotspot for ligand binding which is targeted by our active compounds investigates the binding mode of active compounds and it was identified that compounds preferentially bind in the allosteric binding sites of α-glucosidase. The results obtained from docking study suggested that the carboxylic group is responsible for their biologic activities. Furthermore, the α-glucosidase inhibitory potential of the active compounds is reported here for the first time.
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spelling doaj.art-ec6fa3ec810440e59af756481e561e8c2023-11-20T00:12:29ZengMDPI AGBiomolecules2218-273X2020-05-0110575110.3390/biom10050751Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico StudiesNajeeb Ur Rehman0Sobia Ahsan Halim1Mohammed Al-Azri2Majid Khan3Ajmal Khan4Kashif Rafiq5Ahmed Al-Rawahi6Rene Csuk7Ahmed Al-Harrasi8Natural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanOrganic Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Str. 2, D-06120 Halle (Saale), GermanyNatural & Medical Sciences Research Center, University of Nizwa, P.O Box 33, Birkat Al Mauz, Nizwa 616, OmanFourteen triterpene acids, viz., three tirucallane-type (<b>1</b>–<b>3</b>), eight ursane-type (<b>4</b>–<b>11</b>), two oleanane-type (<b>12</b>, <b>13</b>) and one lupane type (<b>21</b>), along with boswellic aldehyde (<b>14</b>), α-amyrine (<b>15</b>), epi-amyrine (<b>16</b>), straight chain acid (<b>17</b>), sesquiterpene (<b>19</b>) and two cembrane-type diterpenes (<b>18</b>, <b>20</b>) were isolated, first time, from the methanol extract of <i>Boswellia elongata</i> resin. Compound (<b>1</b>) was isolated for first time as a natural product, while the remaining compounds (<b>2</b>‒<b>21</b>) were reported for first time from <i>B. elongata.</i> The structures of all compounds were confirmed by advanced spectroscopic techniques including mass spectrometry and also by comparison with the reported literature. Eight compounds (<b>1</b>–<b>5, 11, 19</b> and <b>20</b>) were further screened for in vitro α-glucosidase inhibitory activity. Compounds <b>3</b>–<b>5</b> and <b>11</b> showed significant activity against α-glucosidase with IC<sub>50</sub> values ranging from 9.9–56.8 μM. Compound <b>4</b> (IC<sub>50</sub> = 9.9 ± 0.48 μM) demonstrated higher inhibition followed by <b>11</b> (IC<sub>50</sub> = 14.9 ± 1.31 μM), <b>5</b> (IC<sub>50</sub> = 20.9 ± 0.05 μM) and <b>3</b> (IC<sub>50</sub> = 56.8 ± 1.30 μM), indicating that carboxylic acid play a key role in α-glucosidase inhibition. Kinetics studies on the active compounds <b>3</b>–<b>5</b> and <b>11</b> were carried out to investigate their mechanism (mode of inhibition and dissociation constants <i>K<sub>i</sub></i>). All compounds were found to be non-competitive inhibitors with <i>K<sub>i</sub></i> values in the range of 7.05 ± 0.17–51.15 ± 0.25 µM. Moreover, in silico docking was performed to search the allosteric hotspot for ligand binding which is targeted by our active compounds investigates the binding mode of active compounds and it was identified that compounds preferentially bind in the allosteric binding sites of α-glucosidase. The results obtained from docking study suggested that the carboxylic group is responsible for their biologic activities. Furthermore, the α-glucosidase inhibitory potential of the active compounds is reported here for the first time.https://www.mdpi.com/2218-273X/10/5/751<i>Boswellia elongata</i>triterpene acidsα-glucosidase inhibitorsNMR spectroscopykinetics studyhomology modeling
spellingShingle Najeeb Ur Rehman
Sobia Ahsan Halim
Mohammed Al-Azri
Majid Khan
Ajmal Khan
Kashif Rafiq
Ahmed Al-Rawahi
Rene Csuk
Ahmed Al-Harrasi
Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies
Biomolecules
<i>Boswellia elongata</i>
triterpene acids
α-glucosidase inhibitors
NMR spectroscopy
kinetics study
homology modeling
title Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies
title_full Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies
title_fullStr Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies
title_full_unstemmed Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies
title_short Triterpenic Acids as Non-Competitive α-Glucosidase Inhibitors from <i>Boswellia elongata</i> with Structure-Activity Relationship: In Vitro and In Silico Studies
title_sort triterpenic acids as non competitive α glucosidase inhibitors from i boswellia elongata i with structure activity relationship in vitro and in silico studies
topic <i>Boswellia elongata</i>
triterpene acids
α-glucosidase inhibitors
NMR spectroscopy
kinetics study
homology modeling
url https://www.mdpi.com/2218-273X/10/5/751
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