The art of healing has its origin from the antiquity of human civilization. Man as a savage, must have known by experience how to relieve his sufferings by the use of herbs growing around him. The historical survey of traditional medicine reveals that in his search for food the primitive man began to distinguish those plants suitable for nutritional purposes from others possessing definite pharmacological actions. Thus the drugs from plant origin have served through the ages as the mainstay for the treatment of a variety of ailments and preservation of human health. A large reservoir of plant based medicines has been provided in the early period covering the Indian, Chinese Sumerian, Egyptian Assyrian and Muslim civilizations. In the Indo-Pakistan sub-continent studies in the chemical constituents of indigenous medicinal plants have been carried out at various research centers to serve the dual purposes of broadening pharmacopial spectrum and providing a basis for therapeutic study directed towards the syntheses of drugs modeled on chemical structure of natural products. In this context it is of special interest to note that the largest and the most sophisticated nucleus for the systematic investigations in the chemistry of biologically active principles of indigenous medicinal plants is based at Karachi under the name of HEJ Research Institute of Chemistry, which is presently under the directorship of famous Plant Chemist of Pakistan, Prof. Dr. Atta-ur-Rahman.
Taking into account the facts stated above, the work undertaken for the present doctoral dissertation relates to the isolation and structural studies of new natural products from two indigenous medicinal plants of Pakistan namely Mimusops elengi and Mentha longifolia. The thesis is, therefore, divided into two parts entitled:
PART-A Bioassay directed isolation on Mimusops elengi
PART-B Phytochemical studies on Mentha longifolia
PART-A: Bioassay directed isolation on Mimusops elengi.
Mimusops elengi, belongs to the family Sapotaceae, is a tree growing in the subcontinent . The plant is reported to have medicinal uses for treatment of asthma, diarrhea, fever, headache, rheumatism,sore eye and strengthening of gums . Pharmacological studies showed that this plant possesse diuretic , spermicidal , spasmolytic  and antimycotic activities The systematic bioassay directed isolation studies on the whole plant material, collected from Karachi region, have led to the isolation and structure elucidation of six new compounds including two new steroidal glycosides 68-69, three pentacyclic triterpenes of ursene series 70-72, and a new triterpene of lupene series 73, respectively. Besides these, one unreported and seven reported compounds have also been isolated and characterized.
(1) (24r)-Stigmast-7, 22 (E)-dien-3a-ol 3-o-B-D-glucopyranoside (68) (2) (24R)-Stigmast-7,22 (E)-dien-o1 3-o-B-D-galactopyranoside (69) (3) 3B, 6B, 19a, 23-Tetrahydroxy-urs-12-ene (70) (4) 3B-(p-Hydroxy-cis-cinnamoyloxy) urs-12-en-28-oic acid (71) (5) 3B, 19a, 23-Trihydroxy-urs-12-ene (72) (6) 1B-Hydroxy-3B-hexanoyl-lup-20 (29)-ene-23, 28-dioic acid (73) Compound isolated for the first time from M. elengi (1) 3B-(p-Hydroxy-trans-cinnamoyloxy) urs-12-en-28-oic acid (74)
PART-B: Phytochemical studies on Mentha longifolia Mentha longifolia belongs to the family Labiatae. It is a perennial herb having white creeping rhizomes, with a strong aromatic odour. It is commonly known as horsemint, which is considered carminative, antiseptic and stimulant . Some bioactive aroma containing chemicals have previously been reported from M longifolia [15-7] Phytochemical studies on the whole plant material, collected from qamber Swat, have resulted in the isolation and structure elucidation of a new flavonoid 5,8,4 â€“ trihydroxy-6,7,3- trimethoxyflavone (107), along with five known compounds: mearnsitrin (4- o â€“methyl-myricetin 3-o-L-rhamnoside) (108), 5,7- dihydroxy-4methoxyflavone (109), 5-hydroxy-6, 7, 3, 4-tetramethoxy-flavone (110), 5-hydroxy-7,8,2,3-tetranettoxyflavone (111), and ursolic acid (112). 5,8,4-Trihydroxy-6,7,3- trimethoxyflavone (107)
New source compounds from mantha longifolia
1.Mearnsitrin (4-o-methyl-myricetin 3-o-L-rhamnoside) (108). 2.5-Hydroxy-6,7,3,4-tetranettoxyflavone (110). 3.5-Hydroxy-7,8,2,3- tetramethoxyflavone (111). The structures of all the compounds have been elucidated through chemical transformations and modern spectroscopic techniques including ID and 2D NMR.