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ORIGINAL ARTICLE
Year : 2015  |  Volume : 6  |  Issue : 1  |  Page : 11-19  

Insignificant antitubercular activity of pyrazoline, phenyl pyrazoline and isoxazoline moiety in lupeol


Department of Pharmaceutical Chemistry, Institute of Pharmacy, Pranveer Singh Institute of Technology, Kanpur, Uttar Pradesh, India

Date of Web Publication20-May-2015

Correspondence Address:
Vandana Khattar
Institute of Pharmacy, Pranveer Singh Institute of Technology, Kanpur, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-9234.157379

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   Abstract 

Aim: The Present study is to investigate the antimycobacterial activity of pyrazoline, phenyl pyrazoline and isooxazoline moiety containing lupeol. The main purpose to show insignificant antimicrobial activity of these lupeol derivatives and hence that further researchers do not waste time to investigate antitubercular activity of these group containing lupeol derivatives. Materials and Methods: Lupeol has been isolated from Crataeva nurvala and its reported antitubercular activity prompted to prepare semisynthetic derivatives to know how much they show antitubercular activity. Newer substituted derivatives of lupeol were synthesized by firstly oxidation of lupeol to lupeol aldehyde followed by replacement of aldehydic group by various groups as pyrazoline, phenyl pyrazoline and Isooxazoline. These Pyrozoline, Phenyl pyrazoline and Isooxazoline derivatives are synthetic analogues of the naturally occurring triterpenoid lupeol from the plant crataeva nurvala, were tested for their spectral data and conformation of the groups, then tested these derivatives of lupeol for antitubercular activity against Mycobacterium tuberculosis (MTB) strain H37Rv using the Microplate Alamar Blue Assay. Result: The result indicate that pyrazoline, Phenyl pyrazoline and Isooxazoline moiety containing lupeol derivatives did not show antimycobacterial activity against MTB at 50 μgm/ml. Conclusion: Pyrazoline, Phenyl pyrazoline and Isooxazoline derivative of lupeol did not have significant antimycobacterial activity. Thus, further optimization of it is needed.

Keywords: Crataeva nurvala, lupeol aldehyde, Microplate Alamar Blue Assay, Mycobacterium tuberculosis, semisynthetic


How to cite this article:
Khattar V, Wal A, Rai A K. Insignificant antitubercular activity of pyrazoline, phenyl pyrazoline and isoxazoline moiety in lupeol. J Pharm Negative Results 2015;6:11-9

How to cite this URL:
Khattar V, Wal A, Rai A K. Insignificant antitubercular activity of pyrazoline, phenyl pyrazoline and isoxazoline moiety in lupeol. J Pharm Negative Results [serial online] 2015 [cited 2019 Sep 22];6:11-9. Available from: http://www.pnrjournal.com/text.asp?2015/6/1/11/157379


   Introduction Top


Tuberculosis is a chronic granulomatous disease and a major problem in developing countries. It is a chronic bacterial infection, spread through the air, and caused by a bacterium called Mycobacterium tuberculosis (MTB) aerobic bacilli belonging to the Mycobacteriaceae, which can mainly attack the lungs, although can affect other organs as well. [1] The goals of tuberculosis control are to cure active disease, prevent relapse, reduce transmission and avert the emergence of drug-resistance. Therefore, the ability of new chemotherapeutic agents should be to meet these aims more efficiently. [2] Actually, a good number of plant secondary metabolites are reported to have antitubercular activity comparable to the existing antitubercular drugs or sometimes even better in potency. [3],[4]

In this research work, we adopt the semisynthetic method. Semisynthesis or partial chemical synthesis is a type of chemical synthesis that uses compounds isolated from natural sources (e.g. plant material or bacterial or cell cultures) as starting materials. Semisynthesis is, usually, used when the precursor molecule is too structurally complex, too costly or too inefficient to be produced by total synthesis. [5] Many medicinal important plant derived compounds include quinine, vindesine, Taxol, digoxin etc., show different therapeutic activity. [6] Crataeva nurvala is a plant used in Indian Ayurvedic Medicine. It is also known as Three-leaved Caper, Varuna (Sanskrit). [7],[8],[9],[10] It belongs to the Family: Capparidaceae. Among potential antitubercular agents heterocyclic compounds represent an outstanding drug moiety. [11] Pyrazolines and isoxazoline are well known, and important 5-membered heterocyclic compounds, and various methods have been worked out for their synthesis. [12] Diversely substituted pyrazolines, Phenyl pyrazoline and isoxazoline and their derivatives embedded with a variety of functional groups are important biological agents, and a significant amount of research activity has been directed towards this class. In particular, they are used as antitumor, antibacterial, antifungal, antiviral, antiparasitic, anti-tubercular and insecticidal agents. [13],[14],[15],[16]


   Materials and methods Top


Isolate the lupeol from the stem bark of Crataeva nurvula. Their purification is done by using column chromatography using silica gel (60-120 mesh) from CDH laboratory (India). All the reactions were monitored by thin layer chromatography using stationary phase as silica gel of SDFCL (India) and mobile phase as taking different solvent mixtures as n-hexane and EtOAc; Benzene - Methanol; Chloroform - EtOAc, etc., Plates were visualized by iodine vapors or by spraying with 5% H 2 SO 4 in MeOH, followed by heating the plates in the oven (110°C). The plates were also visualized in ultraviolet light. Melting points of compounds were measured in open capillaries in electrical heated melting point apparatus of Jindal, S.M. Scientific Instruments Pvt. Ltd., New Delhi. Synthesize derivatives of lupeol under many schemes. IR spectra were recorded on Simadzu-8400S, Simadzu, Japan FTIR spectrometer and values are expressed in wave numbers (cm−1 ). 1 H-NMR spectrums were recorded on JEOL, 500 MHz FT-NMR, USA using CDCl 3 as solvent. Tetramethylsilane (TMS, d0.00 ppm) was used as an internal standard in 1 H NMR. Chemical shifts are expressed in descending order (from down field to up field signals). 1 H-NMR data is given in the manner for, e.g. d1.75 (t, 2H, J = 6.7 Hz, H)-where alphabets s, d, t and m displays multiplicity of signals as singlet, doublet, triplet and multiplet respectively, secondly the number of protons for particular signal, next is coupling constant for splitting, and finally the protons or carbon for which signal is assigned. Electron ionization mass spectra were recorded on WATERS-Q-T of Premier-HAB213 mass spectrometer. Antitubercular activity was performed by Microplate Alamar blue Assay (MABA) against MTB H 37 Rv strain from CDRI.

Collection of the plant part

Stem bark of Crataeva nurvala was collected from HBTI, Kanpur in October 21, 2011. The plants were selected on the basis of their folk medicinal value.

Extraction and isolation of lupeol (1)

The air dried Stem bark of Crataeva nurvala (950 gm) was grinded and extracted with commercial alcohol (95% Ethanol) in a Soxhlet apparatus at an elevated temperature. The extract was separated from the plant debris by filtration. The extract was concentrated by evaporation under reduced pressure at 40°C using Buchi rotary evaporator to have gummy concentrate of reddish black color. Collective mother liquor was chromatographed over normal silica gel, packed in hexane. Elution of the column first with n-hexane, increasing amount of ethyl acetate in hexane. 7-10% Ethyl acetate in hexane eluent gave lupeol (2 g), which is detected on TLC plates by spraying with vanillin-H 2 SO 4 reagent and also detected by exposure of iodine vapour.

The IR spectrum showed hydroxyl group (3326.6 cm -1 ), vinyldiene group 2923.4, 1743.8, 878 cm−1 respectively in [Figure 1]. In 1 H-NMR spectrum a pair of two singlets at 4.68 and 4.56 along with a singlet for 3 protons at 1.68 is indicating for the presence of isoprenyl side chain present in the molecule. Six singlets for 3 protons each and a multiplet for one proton at3.23 is as according to the six methyl groups and H-3 proton concentrated with OH, present in lupeol, represented in [Figure 2].
Figure 1: I.R. Spectra of Lupeol

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Figure 2: 1H NMR (500MHz, CDCl3) Spectra of Lupeol

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M.P: 212-214°C; I.R: nmax (cm − 1 ): 3326.6, 2923.4, 2867.1, 1743.79, 1455.9, 1381, 1263.8, 1165.4, 1104.5, 1032.28, 878, 799.9; Mass (ESI): m/z 427 (M + 1); 1 H-NMR (500 MHz, CDCl 3 ): d 4.67 and 4.09 (2 s, 1 H each, H-29), 3.27 (m, 1 H, H-3), 2.52 (m, 1 H, H-2), 1.99 (m, 1 H, H-19), 1.68 (s, 3H, H-30), 1.62-1.25 (bunch for 24 H), 1.02 (s, 3H), 0.96 (s, 3H), 0.94 (s, 3H), 0.82 (s, 3H), 0.78 (s, 3H), 0.76 (s, 3H).

General procedure for the synthesis of lupeol derivatives

The synthesis of (Lupa-21, 20 (29) dien, 3-beta-ol) (3β)-Lup-20 (29)-en-3-0l derivatives (LD - 1-5) respectively was described in Scheme 1 [Additional file 1].

General procedure for the synthesis of lupeol aldehyde (2)

Allylic oxidation of lupeol with SeO 2 in moist dioxane under refluxing condition gave the aldehyde (2).

Lupeol (1.5 g) was refluxed with selenium dioxide in dioxane with 3-4 drops of distilled water, for 24 h. After consumption of all of lupeol, the reaction mixture was passed through ciliate, treated with 2.5% aq. KOH, and was extracted with chloroform. Organic layer was washed with distilled water till it became neutral, dried over sodium sulfate, and was evaporated in vacuum. this reaction mixture was chromatographed over silica gel column, packed in Hexane and was eluted with hexane, 5, 10, and 20% ethyl acetate/hexane Elution with 20% ethyl acetate/hexane gave the required product lupeol aldehyde (2) in yield (50%).

Formation of the compound (2) generated an additional functional group (Aldehyde) in lupeol that can be used to build different heterocycles on this bi-functional three carbon unit. The IR spectrum is shown in [Figure 3] and in NMR spectrum, a new proton at 9.5 appeared along with olefinic proton show aldehyde group.
Figure 3: I.R. of Lupeol aldehyde

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IUPAC: 2-(9-hydroxy-3a, 5a, 5b, 8, 8, 11a-hexamethylicosahydro-1H-cyclopenta[a] chrysen-1-yl) acryl aldehyde.

M.P: 222-225°C; I.R: nmax (cm-1): 3326, 2945.9, 2855, 2325, 1743.1, 1641.98, 1454.4, 1380.51, 1261.34,1109, 1015.34, 948.1, 757.19; Mass (ESI): m/z 441 (M + 1); 1 H-NMR (300 MHz, CDCl3): d9.48 (s, 1 H-CHO), 6.25 and 5.87 (2 s, 1 H each, H29), 3.13 (m, 1 H, H-3), 2.76 (m, 1 H), 2.10 (m, 1 H), 1.65-1.27 (bunch, 24 H), 1.01 (s, 3H, -Me), 0.96 (s, 3H, -Me), 0.92 (s, 3H, -Me), 0.81 (s, 6H), 0.75 (s3H, -Me).

General procedure for the synthesis of compound (3)

In order to this, various changes are done in the isopropenyl side chain of the lupeol. For this phenyl keto substituted, derivative of lupeol (3) was synthesized by the action of acetophenone and rectified spirit on lupeol aldehyde (2) in the presence of alkali. The compound (3) on further changes leads to various compounds that show activity against tuberculosis. For this, Place a solution of 0.2 gm. NaOH in 1.36 ml. Water and 7.5 ml. of rectified spirit in bolt head flask provided with mechanical stirrer. Then immense the flask in batch of crushed ice. Pour freshly derived acetophenone (0.0023 mol, 276 mg.) in to the above mixture. Start stirring and then add 200 mg of pure lupeol aldehyde (2). Kept the temperature of mixture is about 25°C and stir vigorously until the mixture is thick. Remove stirrer and leave the reaction mixture in an ice bath on refrigerator overnight. Finally, filtered the mixture using Whatman filter paper gave the required product (3).

IUPAC: 4-(9-hydroxy-3a, 5a, 5b, 8, 8, 11a- hexamethylicosahydro-1Hcyclopenta[a] chrysen-1-yl)- 1phenylpenta-2,4-dien-1-one.

M.P: 215-219°C, I.R.: nmax (cm−1 ): 3286.9, 2948.8, 2867.1, 2700, 1744, 1678, 1619.6, 1468, 1378.7, 1188.3, 1106.6, 1040.6, 1013.4, 951.19, 982.28, 873.46, 706.35; Mass (ESI): m/z 543(M + 1), 1 H-NMR (500 MHz, CDCl3):7.25(s, 1H), 6.59(s, 1H), 4.58(s, 1H), 3.18-3.16 (m, 1H), 2.18-2.22(t, 9H), 1.65 (s, 1H), 1.19-1.2(d, 6H), 1.65-1.27 (bunch, 24 H),1.01 (s, 3H, -Me), 0.96 (s, 3H, -Me), 0.92 (s, 3H, -Me), 0.81 (s, 6H), 0.75 (s, 3H, -Me). NMR of compound 3 is shown in [Figure 4].
Figure 4: 1H NMR (500MHz, CDCl3) Spectra of Compound (3)

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General procedure for the synthesis of compound (4a) and (4b)

The phenyl keto group crafted on lupeol aldehyde was converted to pyrazoline analogues. This was done by reaction of the compound (3) with hydrazine derivatives in the solvent ethanol. These reaction lead to the formation of compounds (4a) and (4b).

Compound (4a)

The mixture of (3) (0.0004 mol, 200 mg) reacted with ethanol and then hydrazine hydrate (0.0004 mol, 20 mg.) added drop-wise in the reaction mixture in a round bottom flask. The reaction mixture was heated under reflux for 24 h. Cooled the reaction mixture and poured into crushed ice with constant stirring. Then filter the mixture gave residue that recrystallize with the ethanol and dried the product (4a). The obtained compound is confirmed by IR [Figure 5], NMR [Figure 6] and Mass spectroscopy [Figure 7].
Figure 5: I.R. of Compound (4a)

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Figure 6: 1H NMR (500MHz, CDCl3) Spectra of Compound (4a)

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Figure 7: MS of the compound (4a)

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IUPAC: 3a, 5a, 5b, 8, 8, 11a-hexamethyl-1- (1-(5-phenyl-4,5-dihydro-1H-pyrazol-3-yl) vinyl) icosahydro 1H-cyclopenta[a] chrysen-9-ol.

M.P: 200-210°C, I.R: nmax (cm − 1): 3326.15, 2938.2, 2861, 1641.5, 1556.1, 1457.23, 1489, 1258, 1045, 809, 685; Mass (ESI): m/z 557(M + 1), 1H-NMR (500 MHz, CDCl3): 8.21-8.18 (m, 2H), 7.96-7.25 (m, 7H), 5.6-5.2 (m, 1H), 4.28-4.029 (m, 18H), 3.67 (m, 1H, H-3), 2.155 (m, 1H, H-2), 2.04 (m, 1H, H-19), 1.39-1.11 (bunch, 24 H),1.08 (s, 3H, -Me), 1.07 (s, 3H, -Me), 0.87 (s, 3H, -Me), 0.86 (s, 6H), 0.84 (s, 3H, -Me).

Compound (4b)

A mixture of (3) (0.0004 mol, 200 mg) reacted with ethanol and then Phenyl hydrazine (0.0004 mol, 53 mg.) added drop-wise in the reaction mixture in the round bottom flask. The reaction mixture was heated under reflux for 24 h. Cooled the reaction mixture and poured into crushed ice with constant stirring. Then filter the mixture gave residue that recrystallize with the ethanol and then dried the product (4b). This product structure is confirmed by IR [Figure 8], NMR [Figure 9] and Mass spectroscopy [Figure 10].
Figure 8: I.R. of Compound (4b)

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Figure 9: 1H NMR (500MHz, CDCl3) Spectra of Compound (4b)

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Figure 10: MS of the compound (4b)

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IUPAC: 1-(1-(1, 5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl) vinyl)-3a, 5a, 5b, 8, 8, 11a hexamethyl icosa hydro-1H-cyclopenta[a] chrysen-9-ol.

M.P: 190°C; I.R: nmax (cm−1 ): 3326.15, 2972.81, 2882.18, 1622, 1453.59, 1380.32, 1326.85, 1273.39, 1087.12, 1045.26, 879.56; Mass (ESI): m/z 633(M + 1), 1 H-NMR (500 MHz, CDCl3): d8.08 (s, 1H), 7.87 and 7.84 (s, 1H each),7.7(t, 1H), 7.58-7.39(m, 6H), 7.25(s, 2H), 6.54-6.42(m, 1H), 2.3-2.2 (m, 1H, H-3), 1.73 (m, 1H, H-2), 1.41 (m, 1H, H-19), 1.28 (d, 2H,), 1.27-1.24 (bunch, 24 H),1.10 (s, 3H,-Me), 0.88 (s, 3H,-Me), 0.87 (s, 3H, -Me), 0.85 (s, 6H), 0.06 (s3H, -Me).

General procedure for the synthesis of compound (5)

The phenyl keto group crafted on lupeol aldehyde was converted to oxazoline analogues. This was done by reaction of the compound (3) with hydroxyl amine in the solvent DMF. These reaction lead to the formation of compounds (5). A mixture of (3) (0.0004 mol, 200 mg) in DMF (3.10 ml.) and hydroxylamine (0.0004 mol, 0.03 gm) refluxed for 24 h. Then reaction mixture was cooled and poured into ice cooled water with stirring. The separated solid filtered, washed with water, dried and recrystlize with dioxane. Finally, dried the product, which is confirmed by IR [Figure 11], NMR and Mass spectroscopy.
Figure 11: I.R. of Compound (5)

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IUPAC: 5a, 5b, 8, 8, 11a-pentamethyl-1-(1-(5-phenyl-4, 5-dihydroisoxazol-3yl) vinyl) icosahydro-1H cyclo penta[a] chrysen-9-ol.

M.P: 150°C; I.R: nmax (cm − 1 ): 3301, 2943, 2869, 1640, 1538.38, 1452.28, 1377, 1381.83, 1260, 1103.97, 1041.36, 1014, 880.9, 794.8; Mass (ESI): m/z 559(M + 1), 1H-NMR (500 MHz, CDCl 3 ): 7.22-8.18(m, 10H, ArH), 5.0-5.2(m, 1H), 4.28-4.029(m, 18H), 3.67 (s, 3H, CH 3 ), 2.70 (s, 2H, CH 2 ), 2.04 (m, 1H, H-19), 1.39-1.11 (bunch, 24 H),1.08 (s, 3H, -Me), 1.07 (s, 3H, -Me), 0.87 (s, 3H, -Me), 0.86 (s, 6H), 0.84 (s, 3H, -Me).

Pharmacological evaluation

Protocol for screening of compounds for antimycobacterial activity

Stock solution


10 mM or 10 mg/ml. compound in DMSO. To be kept frozen in aliquots.

Minimum inhibitory concentration

IC90 determination for all submitted compounds (using 3.125 μM, 6.25 μM, 12.5 μM, 25.0 μM and 50.0 μM conc.) against Mtb H37Rv.

Methodology: Microplate Alamar Blue Assay

10 mM stocks of compounds from various projects. These stocks are diluted into a 96 - well flat bottom plate according the project requirement. 40 μl of DMSO is added to the well of a 96 - well flat bottom plate. 40 μl of the diluted compound is added to the first well of the row, giving a 1:1 dilution of the compound in the first column. 40 μl of isoniazid is used as a positive reference control (stock 0.1 mg/ml). Two fold serial dilutions are done up to 5 concentrations (using 3.125 μM, 6.25 μM, 12.5 μM, 25.0 μM and 50.0 μM conc.). 4 μl of the serially diluted compounds is added to duplicate plates. The plates are labeled. Pre-incubated Medium control is also added. 1:1000 dilution of the freeze-thawed log phase (3-7 × 108 CFU/ml) culture is made in 7H9 broth (+ Tween + Glycerol + CAS + ADC) to give a cell number of 3-7 × 105 CFU/ml. control well contained only this culture with 40 μl DMSO. 200 μl of this culture is added into the wells using multipipette. Serial dilution of the culture used for the MIC assay. On day 5, the culture and media control wells are checked for growth and 25 μl of dye is added to all the wells and incubated for 1 day at 37°C. On day 6, reading is taken at 575 nm and 610 nm and the raw data is exported to a text file. The data is used and MIC is calculated using XL-fit.


   Result and discussion Top


Traditionally medicinal plants have been used in folk medicine throughout the world to treat various diseases. We evaluated effects of lupeol derivatives made from lupeol, which extracted from crataeva nurvala through MABA. All the compounds synthesized, tested at 50 μg/ml. for antitubercular activity. Detailed analysis of results of synthesized compounds showed that formation of pyrozoline, phenyl pyrazoline and isooxazoline lupeol derivatives do not show antitubercular activity at 50 μg/ml. The replacement of C-30 CHO of isopropenyl group in lupeol by pyrozoline, phenyl pyrazoline and isooxazoline ring did not efficient increase the mycobacterial activity of the parent molecule lupeol.


   Conclusion Top


This study reveals that pyrazoline, phenyl pyrazoline and isooxazoline moiety containing lupeol do not efficiently impart in the antitubercular activity. It is thus concluded that lupeol skeleton deserve further investigation for the development of more potent and non-toxic new agents for therapeutic use. Further optimization of it is needed to have a compound of clinical trial.

 
   References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]



 

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