1. ALIKO-DANGOTE HALL, EDO UNIVERSITY IYAMHO 22/06/2017 AT
ALIKO-DANGOTE HALL, EDO UNIVERSITY IYAMHO
22/06/2017
A PAPER PRESENTATION BY
SHITTU, TAWAKALIT OMOLARA
EVALUATION OF SALICYALDEHYDE-DERIVED BAYLIS HILLMAN ADDUCTS AND COUMARIN DERIVATIVES AS POTENTIAL ANTISICKLING COMPOUNDS
                  EVALUATION OF SALICYALDEHYDE-DERIVED BAYLIS HILLMAN ADDUCTS AND COUMARIN DERIVATIVES AS POTENTIAL ANTISICKLING COMPOUNDS by SHITTU, TAWAKALIT OMOLARA is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

2. OUTLINE INTRODUCTION: ANTISICKLING AGENTS
SICKLE CELL DISEASE AND PATHOPHYSIOLOGY
STATEMENT OF RESEARCH PROBLEM
BAYLIS-HILLMAN ADDUCTS & COUMARINS
METHODOLOGY
RESULTS & DISCUSSION
RECOMMENDATION
REFERENCES
ACKNOWLEDGEMENT

3. INTRODUCTION
ANTISICKLING AGENTS These are drugs that interfere with the sickling process in Haemoglobin SS via mechanisms such as induction of foetal haemoglobin (HbF); Gardos channel inhibition (membrane-active agents); scavenging iron overloads and in vivo nitric oxide (NO) generation (Dean and Schecter, 1978).

4. Overview of Sickle cell disease
Sickle cell disease (SCD) is one of the most common haemoglobinopathies ravaging the world population with considerable morbidity and mortality (Ingram, 1956; Pauling et al., 1949).
It results from a point mutation on the β6-globin chain where valine substitutes glutamic acid
Sickle cell disease is prevalent in Africa (WHO, 2011). 16% of the population in Africa has a sickle haemoglobinopathy which is the highest proportion worldwide
The homozygous carrier state results to production of two or more mutant hemoglobin S (HbSS) and suffer clinical symptoms of the disease.

5. N = neutrophils, Ec = endothelial cells, ISCs = irreversibly sickle cells, R = reticulocytes.
Figure 1: The pathophysiology of sickle cell disease (Steinberg and Martin, 1999)

6. Clinical symptoms of SCD
elevation of bilirubin level leading to high incidence of gall stones and impairment of hepatic excretory function
anemia
Spleen sequestration
jaundice
Cell apoptosis
acute chest syndrome, pulmonary hypertension

7. Management of sickle cell disease
Curative therapy: Hematopoietic Stem Cell Transplant (HSCT)
Antisickling drugs:
Fetal hemoglobin inducers:
HbS modifiers:
(De Simon et al., 1982; Steinberg et al., 1997, Mehanna, 2001 ).

8. STATEMENT OF RESEARCH PROBLEM
Hydroxyurea, the only chemotherapeutic agent that has proved efficacious in the management of sickle cell disease, is potentially teratogenic, with variable response, and also having issues of non-compliance in severely affected individuals (Saraceno et al., 2008; Haywood et al., 2011). Hence, there is urgent need for development of antisickling agents that can be used to manage this disease.

9. RATIONALE FOR THE STUDY
Baylis Hillman adducts have become an important class of bioactive compounds with diverse biological activities such as anticancer, antimalarial, molluscidal activities (Dadwal et al., 2006). Coumarins possess broad spectrum of biological activities such as anticoagulant (Cheng et al., 1995), anti-HIV (Olomola, et al., 2014), anti-inflammatory, antioxidant, calcium channel blocker (Yamahara et al., 1989); anti-cancer (Luo et al., 2011).
However, these compounds are yet to be implicated in the management of sickle cell disease.

10. OBJECTIVES OF THE STUDY
(a) to synthesize small libraries of Baylis-Hillman adducts and coumarin derivatives
(b) carry out nucleophilic substitution on the coumarin substrates with urea derivatives.
(c) Characterize these compounds, and
(d) Carry out in vitro antisickling assay on the synthesized compound using HbSS blood from patients in steady state.

11. METHODOLOGY Figure 2: Synthetic pathway to the target compounds
Baylis-Hillman adducts
Figure 2: Synthetic pathway to the target compounds
Hydroxyurea analogues
coumarins
Compounds R1 R2 R3
1 a,b,c, d H
-CSNH2, -CONH2, -NHCSNH2
2a,b,c, d
OEt
- CSNH2, -CONH2, NHCSNH2
3a,b,c, d Br
CSNH2, -CONH2, -NHCSNH2
4 a, b,c,d Cl
CSNH2, -CONH2, NHCSNH2

12. METHODOLOGY CONT’D Structure elucidation:
1H and 13C Nuclear magnetic spectroscopy
FT-IR
Biological evaluation:
All the compounds were screened for in vitro antisickling activities using an established method for reversal and inhibitory assays (Egunyomi et al., 2009).
inhibitory assay
Antisickling assay experiments
reversal assay
Na2S2O5 was used as the deoxygenating agent
Positive controls are

13. RESULTS AND
DISCUSSION

14. SYNTHESIS
Figure 3: IR spectrum of tert-Butyl-3 hydroxy -3-( 5-chloro-2-hydroxyphenyl -2-methylenepropanoate) 4b

15. Figure 4: 1H NMR of tert-Butyl-3 hydroxy -3-( 5-chloro-2-hydroxyphenyl -2-methylenepropanoate) 4b

16. ANTISICKLING RESULTS

17. Figure 5: inhibitory activity of the synthesized compounds and standard drug (vanillic acid)

18. Figure 6: Micrograph showing untreated HbSS cells (Negative control) , viewed at X 400 magnification

19. Figure 7 : micrograph showing the inhibitory activity of compound 3b at 1mg/mL, viewed at x 400 magnification

20. CONCLUSION
The reaction between tert-butylacrylate and salicyaldehyde derivatives afforded the corresponding Baylis-Hillman adducts, which were further cyclized regioselectively to 3-(chloromethyl)coumarins in yields up to 96% using a mixture of hydrochloric and acetic acids
The compounds showed progressive inhibition against sodium metabisulphite induced sickling from 0.5 mg/mL to 4 mg/mL and their activities were comparable with the standard drugs vanillic acid and para-hydroxybenzoic acid

21. FURTHER STUDIES
1. NMR-based mechanistic studies should be carried out to explore protein-ligand interactions.
2. Toxicological properties of the compounds should also be evaluated

22. REFERENCES
De Simone, J., Heller, P., Hall, L. and Zwiers, D. (1982). 5-Azacytidine stimulates fetal
hemoglobin synthesis in anemic baboons. Proc. Natl. Acad. Sci., 79:4428–4431.
Dean, A. and Schechter, A.N. (1978). Sickle cell anaemia: Molecular and cellular bases of therapeutic approaches. N. Engl. J. Med., 299:
Haywood, C., Beach, M. C., Bediako, S., Carroll, C. P., Lattimer, L., Jarrett, D. and Lanzkron, S. (2011). Examining the characteristics and beliefs of hydroxyurea users and nonusers among adults with sickle cell disease. Am. J. Hematol., 86 (1): 85–87.
Ingram, V.M. (1956). A specific chemical difference between the globins of normal human and sickle-cell hemoglobin. Nature, 178: 792–794
Mehanna, A.S. (2001). Sickle cell anemia and antisickling agents then and now. Curr. Med.
Chem., 8(2):79-88.
Olomola, T.O., Klein, R. and Kaye, T. (2014). Towards the synthesis of Coumarin derivative
as potential dual-action HIV-1 protease and reverse transcriptase inhibitors. Tetrahedron, 70:

23. ACKNOWLEDGEMENT
Special thanks to Edo University Iyamho for generous financial support which enabled me to present part of this research findings at the TWAS-NYA conference.

24. THANK YOU FOR LISTENING
                  EVALUATION OF SALICYALDEHYDE-DERIVED BAYLIS HILLMAN ADDUCTS AND COUMARIN DERIVATIVES AS POTENTIAL ANTISICKLING COMPOUNDS by SHITTU, TAWAKALIT OMOLARA is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.