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Title of Thesis

Munawwer Rasheed
Institute/University/Department Details
University of Karachi/ H.E.J. Research Institute of Chemistry
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
zadirachta indica a. juss, naeem, houseflies, mosquitoes, pesticide, anopheles stephensi, terpenoids, terpenes, prenylogues, squalenes, a. indica

The present studies have been undertaken on the ethanolic extract of fresh fruit coatings of Azadirachta indica A. Juss, (Neen) following a bioassay guided isolation in the light of our observation that (i) the coatings extract exhibited a larger degree of efficacy on houseflies and mosquitoes as compared to that of seeds and (ii) azadirachtin, the most potent naturally occurring pesticide found in neem is not present in the extract of coatings in any detectable amounts.

The pesticidal activity guided isolation against 4th instar larvae of mosquito, Anopheles stephensi (Orangi Town wild strain), a carrier of malarial parasite, led to the isolation of sixteen triterpenoids, including six new and ten known compounds as listed below. Two of the new constituents, namely meliacinin and azadironic acid represent the skeleton of biogenetic interest. Twelve of these were investigated for the aforementioned biological activity.

Beside these, several other constituents have also been identified (listed below) from the non-polar and less polar fractions showing considerable pesticidal activities. These compounds including sixteen hydrocarbons, one monoterpene, one sesquiterpene, three aromatics, three benzopyranoids and tree fatty acide esters were identified using GC-FID and GC-MS. Their identifies were also supported by other spectroscopic techniques.

Hydrolysis of the major component of neem i.e. azadiradione (2), was attempted under Zemplin conditions to deacetylate C-7 and relate the pesticidal activity with the structure. Fair amounts of required products (44) was obtained along with another product (45). Their pesticidal activity was also performed to extend the structure pesticidal activity relationship.

The structures of the new compounds have been elucidated through sophisticated modern spectroscopic methods including UV, IR, MS, 1H-NMR and 13C-NMR, 2D-NMR experiments and chemical transformations. The known compounds have been identified through comparison of their physical and spectral data with those reported for the corresponding compounds in literature.

Altogehter forty-five compounds are reported in the present thesis, sixteen of which were isolated and teir structures elucidated, whereas twenty-seven compounds were identified through GC-FID and GC-MS. Two analogues were obtained through hydrolysis of Azadirdione. The isolated compounds included six newa,b,c and ten previously reported constituents. The compounds identified through GC, included eight compounds, identified for the first time from fruit coatings, which are marked with the superscript ‘f and fifteen compounds hitherto unreported from any part of neem prior to these studies, which are marked with the superscript ‘g’. The LC50 against An. Stephensi of isolated compounds and of the fractions subjected to GC is given in parenthesis.c,d,e A discussion of the presticidal activity with reference to chemical structures has also been made.

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1769.17 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
57.06 KB
2 1 Summary 1
66.44 KB
3 2 General Introduction 6
52.72 KB
4 3 Biosynthesis of Terpenoids 11
215.4 KB
  3.1 Introduction to Terpenes 11
  3.2 Biosynthesis of the Active Isoprene Units (C 5 ), IPP and DMAPP 13
  3.3 Biosynthesis of the Prenylogues and Squalenes 15
  3.4 Cyclisation and Rearrangement of SQ and OS to form Polycyclic Triterpenoids with Particular Reference to those of A. indica A. Juss (Neem) 20
5 4 Literature Review of Azadirachta Indica A. Juss (Neem) 36
508.36 KB
  4.1 Introduction to Plant 36
  4.2 Medicinal and Pharmacological Importance 37
  4.3 Pesticidal Importance 43
  4.4 Chemical Constituents of A. indica 53
  4.5 Reaction on the Triterpenoids of A. indica 84
  4.6 Introduction to pest 85
6 5 Results and Discussion 86
484.56 KB
  5.1 Present Work 86
  5.2 Characterization/ Identification to Triterpenoids 93
  5.3 Hydrolysis of Azadiradione (2) 118
  5.4 Structure-Pesticidal Activities Relationship Studies 126
  5.5 Qualitative and Qantitative Analysis of Non-Polar to Less Polar Fractions 132
7 6 Experimental 141
395.62 KB
  6.1 General Experimental Procedure 141
  6.2 Plant Material 145
  6.3 Extraction and Isolation/Identification 145
  6.4 Pesticidal Activity 158
  6.5 Physical Data of Fractions ‘A’-‘C 161
  6.6 Characterization of New Triterpenoids 170
  6.7 Hydrolysis of Azadiradione (2) 184
8 7 References 188
228.79 KB
9 8 Appendix 206
25.86 KB