CORRELATION OF THE α-GLUCOSIDASE INHIBITORY ACTIVITY TO METABOLITES OF TETRACERA SCANDENS LEAVES EXTRACTS USING METABOLOMICS AND MOLECULAR DOCKING APPROACHES BY AHMED AHMED MOHAMED NOKHALA A thesis submitted in fulfilment of the requirement for the degree of Master in Pharmaceutical Sciences (Pharmaceutical Chemistry) Kulliyyah of Pharmacy International Islamic University Malaysia JANUARY 2020 ABSTRACT α-Glucosidase inhibition is regarded as an efficient mechanism for management of the postprandial hyperglycemia associated with type 2 diabetes mellitus. The severe gastrointestinal adverse effects have been reported to affect patient`s compliance towards the synthetic α-glucosidase inhibitor drugs and have prompted many studies to discover natural alternatives with comparable efficiency and better tolerability. Tetracera scandens is a traditional medicinal plant, whose leaf has been used for the treatment of diabetes mellitus in Malaysia and other Southeast Asian countries. The α- glucosidase inhibitory potential of T. scandens leaf has not been assessed so far. Hence, this study was aimed to evaluate the α-glucosidase inhibitory potential of T. scandens leaf extracts. Moreover, it aimed to develop and validate a multivariate model to correlate the Fourier transform infrared (FT-IR) spectral fingerprint of the plant extracts to their α-glucosidase inhibitory activity. Another aim of this study was to characterize the putative α-glucosidase inhibitory metabolites of T. scandens extracts using metabolomics approach. Eventually, the affinity of the putative active metabolites towards α-glucosidase was to be predicted through molecular docking study. Different hydromethanolic extracts were prepared and assayed for their α- glucosidase inhibitory potential. The FT-IR spectra of T. scandens extracts were acquired and correlated to their corresponding α-glucosidase inhibitory IC50 values via the orthogonal partial least squares (OPLS) algorithm. Furthermore, the mass spectral data acquired via gas chromatography-mass spectrometry (GC-MS) analysis of the plant extracts was correlated to their α-glucosidase inhibitory IC50 values through an OPLS model, and the putative α-glucosidase inhibitory metabolites were suggested by the loading column plot of the developed model. Moreover, the 3D structures of the putative α-glucosidase inhibitory metabolites were further docked into the active site of Saccharomyces cerevisiae isomaltase in order to predict the ligand-enzyme interactions and affinities. The methanolic extracts of T. scandens leaf showed higher α-glucosidase inhibitory potential as compared to the aqueous ones. The developed OPLS model successfully predicted the α-glucosidase inhibitory potential of new independent T. scandens leaf samples given their fingerprint FT-IR spectra, therefore it can be used as a simple and rapid quality control tool. Moreover, the bands corresponding to the carbon-hydrogen bond (C-H), carbon-carbon double bond (C=C) and carbon-oxygen single bond (C-O) were determined to be positively correlated with the α-glucosidase inhibitory activity of the plant extracts. GC-MS based profiling of the α-glucosidase inhibitory metabolites led to the determination of 6 putative metabolites, namely, palmitic acid, 1-monopalmitin, stearic acid, emodin, catechin and β-sitosterol. Moreover, the metabolites malic acid, 4-hydroxybenzoic acid, xylitol, citric acid, D-fructose, D-glucose, D-mannose and myo-inositol were suggested to induce α-glucosidase activity. The results of the molecular docking study further supported the findings of the metabolite profiling study, since the putative α- glucosidase inhibitory metabolites showed predicted binding energies of -5.9 to -8.8, indicating moderate to high affinities. Conclusively, this study demonstrated the in vitro α-glucosidase inhibitory activity of T. scandens leaf. Furthermore, the metabolomics approach was successfully used to develop a rapid method for quality control of T. scandens leaf and to characterize its putative α-glucosidase inhibitory metabolites. ii خﻻصة البحث IN ARAB يعتبر تثبيط انزيم الفا جلوكوزيداز بمثابة آلية فعالة لعﻻج ارتفاع السكر فى الدم بعد اﻷكل المرتبط بداء السكرى من النوع الثانى. تم اﻹبﻻغ عن اﻵثار الضارة المعوية الحادة التي أثرت على امتثال المريض لﻷدوية المخلقة المثبطة ﻻنزيم الفا جلوكوزيداز ودفعت العديد من الدراسات ﻻكتشاف بدائل طبيعية ذات كفاءة مماثلة و تقبل أفضل. Tetracera scandens هو نبات طبى تقليدى، وقد استخدمت أوراقه لعﻻج داء السكري في ماليزيا ودول جنوب شرق آسيا اﻷخرى. لم يتم تقييم امكانات تثبيط الفا جلوكوزيداز ﻷوراق T. scandens حتى اﻷن. و بالتالى فقد هدفت هذه الدراسة الى تقييم امكانات تثبيط الفا جلوكوزيداز لمستخلصات أوراق .T scandens ، تطوير نموذج متعدد المتغيرات لربط بصمة الطيف باﻷشعة تحت الحمراء FT-IR للمستخلصات النباتية لنشاطها المثبط ﻻنزيم الفا جلوكوزيداز ، تحديد نواتج اﻷيض المفترضة المثبطه ﻻنزيم الفا جلوكوزيداز باستخدام نهج اﻻستقﻻب و التنبؤ بتقارب نواتج اﻷيض النشطة المفترضة تجاه انزيم الفا جلوكوزيداز بواسطة دراسة التقارب الجزيئى. تم تحضير عدة مستخلصات مائية/ميثانولية و تم اختبار امكاناتها التثبيطية على انزيم الفا جلوكوزيداز. تم الحصول على أطياف FT-IR و أطياف الكتلة لهذه المستخلصات و تم ربط كل منها بقيم IC50 المثبطة ﻻنزيم الفا جلوكوزيداز عبر خوارزمية OPLS. تم اختبار تقارب الهياكل ثﻻثية اﻷبعاد لنواتج اﻻيض النشطة المقترحة تجاه الموقع النشط ﻻنزيم isomaltase. أظهرت المستخلصات الميثانولية لورقة T. scandens إمكانات تثبيط أعلى لﻻلفا جلوكوزيداز بالمقارنة مع المستخلصات المائية. لقد تنبأ نموذج OPLS باﻻمكانات التثبيطية ﻻلفا جلوكوزيداز لعينات جديدة مستقلة من ورقة .T scandens باستخدام بصمة اﻷشعة تحت الحمراء الخاصة بها، وبالتالي يمكن استخدامه كأداة بسيطة وسريعة لمراقبة الجودة. عﻻوة على ذلك ، تم تحديد النطاقات المقابلة لرابطة C-H و C=C و C-O لتكون مرتبطة بشكل إيجابي مع نشاط تثبيط اﻻلفا جلوكوزيداز لمستخلصات النبات. أدى تصنيف نواتج اﻷيض ذات التأثير المثبط ﻻنزيم الفا جلوكوزيداز الى تحديد ستة مركبات مفترضة و هى حامض النخيل ،1-مونوبالميتين ، حامض اﻻستياريك ، إيمودين ، كاتشين و بيتا سيتوستيرول. لقد دعمت نتائج دراسة التقارب الجزيئي نتائج دراسة تصنيف نواتج اﻷيض ، حيث أظهرت نواتج اﻷيض المفترضة المثبطة ﻻلفا جلوكوزيداز طاقات ربط متوقعة تتراوح بين -5.9 الى -8.8 ، مما يدل على تقارب متوسط الى عالى. بشكل قاطع ، أظهرت هذه الدراسه نشاط تثبيط الفا جلوكوزيداز ﻷوراق T. scandens . عﻻوة على ذلك ، تم استخدام نهج اﻻستقﻻب بنجاح لتطوير طريقة سريعة لمراقبة الجودة ﻷوراق T. scandens و لتحديد المستقلبات المفترضة المثبطة ﻻنزيم الفا جلوكوزيداز. iii APPROVAL PAGE I certify that I have supervised and read this study and that in my opinion, it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis for the degree of Master in Pharmaceutical Sciences (Pharmaceutical Chemistry) ………………………………….. Mohammad Jamshed Siddiqui Supervisor ………………………………….. Qamar Uddin Ahmed Co-Supervisor I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis for the degree of Master in Pharmaceutical Sciences (Pharmaceutical Chemistry) ………………………………….. Alfi Khatib Internal Examiner ………………………………….. Jamia Azdina Jamal External Examiner This thesis was submitted to the Department of Pharmaceutical Chemistry and is accepted as a fulfilment of the requirement for the degree of Master in Pharmaceutical Sciences (Pharmaceutical Chemistry) ………………………………….. Mohamed Sufian Mohd Nawi Head, Department of Pharmaceutical Chemistry iv This thesis was submitted to the Kulliyyah of Pharmacy and is accepted as a fulfilment of the requirement for the degree of Master in Pharmaceutical Sciences (Pharmaceutical Chemistry) ………………………………….. Che Suraya Haji Mohd Zin Dean, Kulliyyah of Pharmacy v DECLARATION I hereby declare that this thesis is the result of my own investigations, except where otherwise stated. I also declare that it has not been previously or concurrently submitted as a whole for any other degrees at IIUM or other institutions. Ahmed Ahmed Mohamed Nokhala Signature ........................................................... Date ......................................... vi INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH CORRELATION OF THE α-GLUCOSIDASE INHIBITORY ACTIVITY TO METABOLITES OF TETRACERA SCANDENS LEAVES EXTRACTS USING METABOLOMICS AND MOLECULAR DOCKING APPROACHES I declare that the copyright holders of this thesis are jointly owned by the student and IIUM. Copyright © 2020 Ahmed Ahmed Mohamed Nokhala and International Islamic University Malaysia. All rights reserved. No part of this unpublished research may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of the copyright holder except as provided below 1. Any material contained in or derived from this unpublished research may be used by others in their writing with due acknowledgment. 2. IIUM or its library will have the right to make and transmit copies (print or electronic) for institutional and academic purposes. 3. The IIUM library will have the right to make, store in a retrieved system and supply copies of this unpublished research if requested by other universities and research libraries. By signing this form, I acknowledged that I have read and understood the IIUM Intellectual Property Right and Commercialization policy. Affirmed by Ahmed Ahmed Mohamed Nokhala ……..…………………….. ……………………….. Signature Date vii DEDICATION This thesis is dedicated to my parents, my beloved