Through the Blanc reaction, a series of novel derivatives of camphor (1a–g) and
camphor sulfonic acid (2a–g) were synthesized and characterized using IR, 1H-
NMR, 13C-NMR, and LC-MS/MS (ESI) analyses. The antimicrobial activity of
these compounds, alongside their parent compounds (a–g), was evaluated
against drug-resistant pathogens including methicillin-resistant Staphylococcus
aureus (MRSA), multi-drug resistant Klebsiella pneumonia (MDR-Kb),
Escherichia coli (FDA control), Acinetobacter baumannii, Pseudomonas
aeruginosa, Candida albicans (CLSI strain), and Cryptococcus neoformans var.
grubii. The conjugation of camphor with quinoxalin-2,3(1H, 4H)-dione (1a)
notably enhanced antibacterial efficacy approximately 8-fold (MIC: 24 µM)
against MRSA. Similarly, the linkage of camphor with isatin (1g) resulted in an
8-fold increase in efficacy against Acinetobacter baumannii (MIC: 26 µM) and a
4-fold increase against MRSA, MDR-Kb, E. coli, P. aeruginosa, and C. albicans
(MIC: 51 µM). Among the derivatives, compounds of benzoin (1e) and salicylic
acid (1f) demonstrated significant efficacy against drug-resistant Candida
albicans, MDR-Kb, and Acinetobacter baumannii. Meanwhile, 6,7-
biphenylquinoxalin 2-sulfonamide/sulfonyl chloride (1b/1d) selectively
inhibited the growth of Gram-negative bacteria. None of the compounds
displayed activity against Cryptococcus neoformans var. grubii. Furthermore,
the new derivatives were assessed for anthelmintic efficacy, with results
indicating significant efficacy (p < 0.05) at 2.5 mg/mL, except for the salicylic
acid hybrids (1f, 2f). In conclusion, camphor hybrids (1a–g) exhibited enhanced
antimicrobial and Anthelmintic efficacy compared to camphor sulfonic acid
hybrids (2a–g). The improved antimicrobial efficacy is attributed to increased
membrane permeability across the cell wall, facilitated by the camphor moiety,
thereby augmenting the lipophilicity of the compounds.
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New semi-synthetic derivatives of camphor and evaluation for their growth inhibitory potential against drug resistant pathogens and Earthworms
1. New semi-synthetic derivatives of camphor and evaluation for their growth
inhibitory potential against drug resistant pathogens and Earthworms
Dr. M. Geethavani, M. Pharm., PhD
Professor & HOD
Department of pharmaceutical Chemistry
Balaji college of Pharmacy
Ananthapuramu, Andhra Pradesh State, INDIA - 515721
Research work
5. Camphor is a waxy, white or transparent solid with a strong aromatic odour
which sublimates at room temperature and melts at 180 °C.
It is practically insoluble in water, but soluble in alcohol, ether, chloroform
and other organic solvents.
In Asia, a major source of camphor is camphor basil (Ocimum
kilimandscharicum).
The East African camphorwood tree (Ocotea usambarensis).
In the 19th century, it was known that nitric acid oxidizes camphor into
camphoric acid, this serves as basis for camphor derivatives.
24-02-2024 Dept. of Pharmaceutical Chemistry 5
6. Used as explosive.
Pest deterrent & preservative.
Used as culinary.
Used as flavouring agent.
Used in cosmetic.
used externally to relieve arthritic and rheumatic pains, neuralgia, and
back pain.
It is often used in steam vapourizors to help control coughs by
producing a local anesthetic action to the throat and to loosen
congestion due to colds.
24-02-2024 Dept. of Pharmaceutical Chemistry 6
7. The rapid emergences of resistant bacteria jeopardize the efficacy of antibiotics
and have turned out as public threat.
The Centers for Disease Control and Prevention (CDC) has categorized the drug
resistant pathogens presented as urgent, serious, and concerning threats, which
are playing key role in antibiotic crisis and financial burden not only on
developing countries like India but also to developed nations like USA.
As per WHO, there should be urgent need of new antibiotics with novel
mechanism to save 10 million people death by 2050.
Till today only combination therapy was the priority to manage resistance, but
the battle was over.
Hence, this work was designed to explore possible semi-synthetic derivatives of
camphor by condensation with various potent pharmacophore such as
qunoxiline, Isatin, salicylic acid etc. for antibacterial potential against drug
resistant infections and anthelmintic activity.
24-02-2024 Dept. of Pharmaceutical Chemistry 7
8. To explore possible new semi-synthetic derivatives of camphor
through methylene bridge using potent antimicrobial pharmacophore
such as salicylic acid, Isatin, benzoin and qunoxiline.
To characterize the structures of new compounds with physical and
spectral data.
To evaluate the antimicrobial / growth inhibitory potential of new
derivatives against drug resistant species.
To evaluate the anthelmintic activity against earthworms.
To develop a structure activity relationship for their growth inhibitory
potential against drug resistant pathogens.
To recommend the future research directions.
24-02-2024 Dept. of Pharmaceutical Chemistry 8
9. Step 2
Step 3
Step 1 Literature survey.
Chemical synthesis and Purification.
Characterization of compounds.
Screening for antimicrobial / anthelmintic potential.
Development of Structure activity relationship.
Make recommendation for further research.
24-02-2024 Dept. of Pharmaceutical Chemistry 9
11. Then the final product
was subjected to
purification process
Reaction was
monitored by
TLC
The reaction mixture was
heated to 700c and stirred
for 5-8 hours
Qunoxiline 2-dione, salicylic acid, Isatin,
benzoin, biphenyl qunoxiline, biphenyl
amine in to 250 ml beaker containing 100
ml of 35 % HCl and 35 ml of
formaldehyde
GENERAL SYNTHESIS PROCEDURE :-
A mixture of
camphor
(0.015 mol)
24-02-2024 Dept. of Pharmaceutical Chemistry 11
31. Name Description Strain Organism Type
Staphylococcus aureus MRSA ATCC 43300 Bacteria G+ve
Escherichia coli FDA control ATCC 25922 Bacteria G-ve
Klebsiellapneumoniae MDR ATCC 700603 Bacteria G-ve
Acinetobacter baumannii Type strain ATCC 19606 Bacteria G-ve
Pseudomonas aeruginosa Type strain ATCC 27853 Bacteria G-ve
Candida albicans CLSI reference ATCC 90028 Fungi Yeast
Cryptococcus neoformans var.
grubii Type strain
H99; ATCC
208821 Fungi Yeast
Microorganisms used in the study
CLSI : Clinical and laboratory standard institute
MDR : Multiple drugs resistant
MRSA : methicillin resistant Staphylococcus aureus
FDA : Food and drug administration
Place of Screening: Data Provided by CO-ADD Community for Open Antimicrobial Drug
Discovery, Institute for Molecular Bioscience, The University of Queensland, 4072 St Lucia
QLD Australia (Project ID: PO319)
24-02-2024 Dept. of Pharmaceutical Chemistry 31
32. Antibacterial data Collection
Inhibition of bacterial growth was determined measuring absorbance at
600 nm (OD600), using a Tecan M1000 Pro monochromator plate reader.
Growth inhibition of C. albicans was determined measuring absorbance at 530
nm (OD530), while the growth inhibition of C. neoformanswas determined
measuring the difference in absorbance between 600 and 570 nm (OD600-570),
after the addition of reassuring (0.001% final concentration) and incubation at
35 °C for additional 2h.
A - [Active] Samples with inhibition values equal to or above 80% and abs (Z-Score)
above 2.5 for either replicate (n=2 on different plates) were classed as actives.
P - [Partial Active] compounds with inhibition values between 50.9% - 79.9% or abs (Z-
Sore) below 2.5.
I - Inactive compounds with inhibition values below 50% or abs (Z-Sore) below 2.5.
Quality control measures in the study
24-02-2024 Dept. of Pharmaceutical Chemistry 32
33. Compound
Code
Sa Hit Ec Hit Kp Hit Pa Hit Ab Hit Ca Hit Cn Hit
ABC1 I I I I I I I
ABC2 I I I I I I I
ABC3 I I I I I I I
ABC4 I I I I I I I
ABC5 I I I I I I I
ABC6 I I I I I P I
ABC7 I I I I I I I
XYZ1 I I I I I I I
XYZ2 I I I I I I I
XYZ3 I I I I I I I
XYZ4 I I I I I I I
XYZ5 I I I I I I I
XYZ6 I I I I I I I
XYZ7 I I I I I I I
Summary of the antimicrobial activity (@ 32 µg/ml)
24-02-2024 Dept. of Pharmaceutical Chemistry 33
34. Compound Code Sa Hit Ec Hit Kp Hit Pa Hit Ab Hit Ca Hit Cn Hit
ABC1 -0.93 -7.73 -0.07 2.95 7.96 4.39 -20.65
ABC2 3.53 1.17 -1.62 6.03 15.80 4.78 -9.63
ABC3 7.26 6.15 10.13 2.01 25.94 9.59 -26.16
ABC4 2.89 5.96 6.80 -7.33 14.33 6.64 -114.97
ABC5 0.12 9.82 10.79 -5.93 17.29 10.10 -103.27
ABC6 -2.89 0.70 8.00 -16.15 8.11 63.29 -97.41
ABC7 39.44 3.87 12.47 9.57 16.92 24.35 -151.11
XYZ1 3.23 4.32 1.59 2.78 7.01 13.50 -28.22
XYZ2 0.93 8.09 9.27 1.23 8.87 7.98 -90.18
XYZ3 2.45 8.03 8.50 -3.61 5.72 6.32 -87.09
XYZ4 7.13 8.38 12.37 0.40 0.28 4.90 -110.15
XYZ5 0.63 3.83 20.09 -1.60 15.06 7.41 -59.20
XYZ6 5.44 0.10 4.13 0.90 11.41 3.94 -11.01
XYZ7 13.71 1.41 9.81 2.58 24.69 7.41 -61.61
% Inhibition data on drug resistant pathogens (@ 32 µg/ml)
24-02-2024 Dept. of Pharmaceutical Chemistry 34
37. Interpretation of results:
Percentage growth inhibition of an individual sample is calculated based on
Negative controls and Positive Controls .
Please note Negative inhibition value mean that the growth rate is higher compared
to the Negative Control.
The growth rates for all bacteria and fungi has a variation of -/+ 10%, which lies in
within expected normal distribution of microbial growth.
Please note Negative inhibition value means that the growth rate is higher compared
to the Positive Control .
The growth rates have a variation of -10% or 10%, which is within the reported
normal distribution of bacterial growth.
Any significant variation is identified by the modified Z-Score, and actives are
selected by a combination of inhibition value and Z-Score.
24-02-2024 Dept. of Pharmaceutical Chemistry 37
38. Specifications of Earth worms:
Indian earthworm Pheretima posthuma (Annelida) were collected from the water
logged areas of soil
Average size of earthworm being 7-10 cm.
The anthelmintic assay was carried as per the method of Ajayieobaet al.
The assay was performed on adult Indian earthworm Pheretima posthuma, due to its
anatomical and physiological resemblance with the intestinal roundworm parasites of
human beings.
Pheretima posthuma worms are easily available and used as a suitable model for
screening of anthelmintic drug
Place of Screening: Drug screening laboratory, Centre for Pharmaceutical Research Unit,
Raghavendra Institute of Pharmaceutical Education and Research (RIPER), Anantapur. (Project
approval ID: RR/2013 -17/UG/11)
24-02-2024 Dept. of Pharmaceutical Chemistry 38
39. Each petridish was placed with 3 worms and observed for paralysis or
death.
Mean time for paralysis was noted when no movement of any sort could
be observed, except when the worm was shaken vigorously; the time
death of worm (min) was recorded after ascertaining that worms neither
moved when shaken nor when given external stimuli.
The test results were compared with Reference compound Albendazole
(1, 2.5, 10 mg/ml) treated samples.
24-02-2024 Dept. of Pharmaceutical Chemistry 39
40. Collection of data:-
The time taken for paralysis and death time of worms were
observed and recorded neither after ascertaining that the worms did
not move neither when shaken vigorously nor when dipped in warm
water (50°C).
Statistical Analysis:-
Worm counts were expressed as mean ± SEM. The
significance of difference between the means was determined by
Student’s t-test using a computer software package and considered as
significant when 𝑃<0. 05.
Death
Paralysis
24-02-2024 Dept. of Pharmaceutical Chemistry 40
41. Compound code 1mg/ml 2.5mg/ml 10mg/ml
Camphor 44.21±4.45* 14:58±1.24* 05:09±0.34*
CSA 60:53±5.33* 22:56±2.22* 12:56±1.12*
ABC-1 60:10±5.24* 10:15±1.56* 02:15±0.16*
ABC-2 15:58±1.45* 10:01±1.23* 05:32±0.44*
ABC-3 18:25±1.26* 13:43±1.28* 10:51±1.31*
ABC-4 17:05±1.44* 15:48±1.46* 06:02±0.54*
ABC-5 29:36±2.33* 14:21±1.32* 12:03±1.18*
ABC-6 56:20±5.36* 48:25±4.48* 09:56±1.02*
ABC-7 24:50±2.35* 22:47±2.22* 13:54±1.13*
XYZ-1 54:26±5.02* 38:58±3.10* 12:55±1.06*
XYZ-2 28:42±2.16* 21:05±2.20* 06:07±0.45*
XYZ-3 20:47±2.12* 18:43±2.32* 10:23±0.56*
XYZ-4 28:43±3.12* 14:23±1.42* 07:09±1.01*
XYZ-5 62:12±7.26* 20:32±1.58* 13:46±1.53*
XYZ-6 56:58±6.36* 42:01±3.13* 13:12±0.54*
XYZ-7 10:50±0.56* 10:49±0.45* 10:52±1.12*
Albendazole 35:32±1.43* 32:48±1.52* 27:23±1.06*
Negative control 160 160 160
Anthelmintic activity against Pheretima posthuma: Mean Paralysis data (in minutes: Seconds (n = 3)
* -p value is less than 0.001 compared to negative control
24-02-2024 Dept. of Pharmaceutical Chemistry 41
45. The designed schemes utilized camphor and camphor sulfonic acids as
hydrophobic scaffold, and qunoxiline, Isatin, salicylic acid, benzoin,
quinolone were used as pharmacophore. The molecules were obtained
through "Blanc reaction” using conventional synthesis. The purity of the
compounds was tested based on the TLC.
24-02-2024 Dept. of Pharmaceutical Chemistry 45
48. • Camphor derivative of selected pharmacopeia relatively more active when
compare to camphor.
• The active observation is true especially for Isatin derivatives and salicylic acid
derivatives.
• The benzoin derivatives exhibited 10-20% inhibition agonist klebsiella pneumonia
(organism).
• Among all compounds Isatin and salicylic acid derivative are exhibited percentage
inhibition of 63 and 25 respectively agonist drug resistance candida albicans.
• None of the compound is agonist Cryptococcus and also pseudomonas aeruginosa.
• The derivative of qunoxiline is exhibited 20% agonist acinetobacter baumannii.
• All compounds exhibited <10% whereas Isatin derivative lone exhibited 40%
inhibition MRSA and 25% agonist candida albicans.
• Over all salicylic acid derivatives of camphor is documented as practically active
agonist drug resistance candida albicans.
Structure activity relationship – Antimicrobial property
24-02-2024 Dept. of Pharmaceutical Chemistry 48
49. Structure activity relationship – Anthelmintic property
• SAR was developed based on comparison of camphor and synthesis derivatives the
following observations are made.
• Out of among all camphor sulphonic acid derivatives were found to be inactive
against earthworms
• The benzoin derivatives of camphor is two times more potent than Camphor
sulphonic acid derivatives
• Attachment of qunoxiline 2,3-dione to camphor or camphor sulphonic acid did not
show any improved anthelmintic activity
• Biphenyl qunoxiline derivatives were found to be relatively more potent.
• However camphor sulphonic acid derivatives of camphor decrease the potency to
half the compounds
24-02-2024 Dept. of Pharmaceutical Chemistry 49
50. • The sulphonyl chloride as well as sulfonamide derivative of qunoxiline with
camphor exhibits equal potency against earthworms.
• Out of all these compounds except Isatin derivatives rest of the compounds exhibit
dose dependent
• The most active compounds of the series are ABC-3 > XYZ-7 > ABC-4 >ABC-2 >
XYZ-3.
• The lipohilicity more than 7 was found to be suitable for anthelmintic activity.
• Isatin lipohilicity is low but it is still potent and show potent activity.
• So that the mechanism of Isatin derivatives will be different from that of qunoxiline
• Overall qunoxiline &Isatin were more active against earthworms salicylic acid
derivatives are drug resistance candida albicans
24-02-2024 Dept. of Pharmaceutical Chemistry 50
51. The semi-synthetic derivatives of camphor exhibited potent
Anthelmintic activity against earthworm with p value of less than 0.001,
whilst the activity towards virulent pathogens was not satisfactory.
However, salicylic acid bearing camphor compound exhibited
considerable inhibition against drug resistant Candida sp., and rest of
the compounds exhibited below 50% inhibition at a concentration of
35µg/ml.
24-02-2024 Dept. of Pharmaceutical Chemistry 51
52. 24-02-2024 Dept. of Pharmaceutical Chemistry 52
1. Dr Alysha Elliott (+61 7 3346 2745) C/O Dr Paul Lovelock (+61 7 3346
2211) Institute for Molecular Bioscience / QBP Bldg 80, Services Rd The
University of Queensland St Lucia, QLD 4072 AUSTRALIA
2. V. Kishor Kumar1*, P. Satheesh Kumar1 and T.Venkatachalam2
Investigation Of Anthelmintic Activity Of Pergularia Daemia Leaves
Pharmacophore 2014, Vol. 5 (1), 44-48 USA CODEN: PHARM7 ISSN
2229-5402
3. Church, John (1797). An inaugural dissertation on camphor: submitted to
the examination of the Rev. John Ewing, S.S.T.P. provost; the trustees &
medical faculty of the University of Pennsylvania, on the 12th of May,
1797; for the degree of Doctor of Medicine. University of Philadelphia:
Printed by John Thompson. Retrieved January 18, 2013.
4. Green, B. G. (1990). "Sensory characteristics of camphor". The Journal of
Investigative Dermatology. 94 (5): 662–6. doi:10.1111/1523-
1747.ep12876242. PMID 2324522.