Introduction:

 Objective and rationality of the present study:

 Medicinal components from plants play many important roles in traditional medicine. People in all continents have long applied poultices and imbibed infusions of hundreds, if not thousands, of indigenous plants, dating back to prehistory (Cowan, 1999). It is estimated that there are about 2,500,000 species of higher plants and the majority of these have not been investigated in detail for their pharmacological activities (Ram el al., 2003). In developing countries, about 80% of the population relies on traditional medicine for their primary health care (Matu and Staden, 2003).

 Since Bangladesh has a vast resource of medicinal plants and majority of our population has to rely upon indigenous system of medication from economic point of view. The high cost of imported conventional drugs and/ or inaccessibility to western health care facility, imply that traditional mode of health care is the only form of health care that is affordable and available to the rural people. On the other hand, even when western health facilities are available, traditional medicine is viewed as an efficient and an acceptable system from a cultural perspective (Munguti, 1997) and as a result, traditional medicine usually exist side by side with western forms of health care.

 Identification and isolation of the active constituents from traditionally used phyto-therapy can ensure the health care of the poor people. In addition, herbal drugs could be scientifically modified for better pharmacological activity and to establish safe and effective drugs and the rationality of the present study lies in meeting the challenge of developing herbal medicines, which needs a systematic research on indigenous medicinal plants for the welfare of the humanity.

 Thus to strengthen the existing health care system, biological analyses of an indigenous plant Polyalthia longifolia (Family: Annonaceae) is the primary objective of the present study.

 The plant family: Annonaceae

 The Annonaceae, also called custard apple family or soursop family, is a family of flowering plants consisting of trees, shrubs or lianas. With about 2300 to 2500 species in 120 to 130 genera, it is the largest family in the Magnoliales. The family is concentrated in the Tropics, with few species found in temperate regions. About 900 species are neotropical, 450 are African, and the other species Asian.

 Members of the Annonaceae have simple, alternate, petiolate leaves with smooth, entire margins. The leaves are arranged in two rows along the stems. There is no stipules. The flowers are radially symmetrical and often bisexual. In most species the 3 sepals are united at the base. There are 6 brown to yellow petals, many stamens in a spiral, and many pistils, each with a one-chambered ovary containing many ovules. The pistils generally remain distinct and develop into berry-like fruits but sometimes they coalesce into multiple fruits like the custard apple. Flowers are sometimes borne directly on large branches or on the trunk.

 Cultivation and uses:

 The large, pulpy fruits of some members are edible, including species of Annona (the custard apple, the cherimoya, the soursop), Asimina (the papaw), Rollinia (the biriba).

Besides bearing edible fruits, some members also have aromatic oil and are used for perfumes or spices. The strong bark is used for carrying burdens in Amazonia. The wood is valued as firewood.

The bark, leaves and roots of some species are used in folk medicines. Besides, pharmaceutic research has found antifungal, bacteriostatic, and especially cytostatic capability of some chemical constituents of the leaves and bark.

 Some species are also grown as ornamental plants, especially Polyalthia longifolia pendula.

      Annonaceae includes about 120–130 genera:

Table 1: 130 genera of Annonaceae family:

Annonaceae species available in Bangladesh:

 Annonaceae plants grow well in Bangladesh. They are found in plain areas as well as in hilly areas like Sylhet and Chittagong. According to the recent reports of Bangladesh National Herbarium, the following Annonaceous plants are available in Bangladesh as shown in the following Table:

Table 2: Annonaceous plants & their medicinal uses are listed below:

Chemistry of the Annonaceae:

 Though there are about 120 genera and more than 2100 species (Trease & Evans, 1993) in the family Annonaceae, chemical investigation has been very limited with only a few GENERA, notably Annona, Ennantia, Goniothalamus, Uvaria and Xylopia have been examined widely. Research carried out on Annonaceous paints till present time revealed that the plants of this family posses many interesting, structurally varied secondary metabolites including alkaloids. Terpenoids & steroids, flavonoids, coumarins, volatile oils, styryl lactones, acetogenins and other Oxygen containing heterocycles. Alkaloids are most probably the major and most widespread group of compounds isolated from the Annonaceae.

A short description about the chemistry of Annonaceae is shown below:

   Terpenoids:

Terpenes consist of five carbon isoprene units, derived from mevalinic acid and are classified according to the number of isoprene units involved. Terpenes are moderately distributed in Annonaceae, Broadly terpenes are classified as

1.         I.    Monoterpenes  (C₁₀)
2.         II.    Sesquiterpenes  (C₁₅)
3.         III.    Diterpenes (C₂₀)
4.         IV.    Triterpenes (C₃₀)

 Almost every type of terpenes is isolated form various genus and species of Annonaceae. Some of them are shown in table 2:

 Table 3 Terpenoids from Annonaceae plants:

FIG: Structural types of terpenoids and steroids found in Annonaceae

 Alkaloids:

More than two hundred alkaloid have been isolated from Annonaceous species. From THE BIOGENETIC point of view, these alkaloids are classified in to two major classes:

1. Isoquinoline alkaloids
2. Non-Isoquinoline alkaloids

1. Isoquinoline alkaloids:

Isoquinoline alkaloids are characterized by Isoquinoline skeleton. Some examples of this type of alkaloids with their subclasses are given in the following Table:

  Table4: Occurrence of Isoquinoline alkaloids in ANNONACEAE

FIG: Structural types of various isoquinoline alkaloids from Annonaceae

  Flavonoids:

 The flavonoid compounds can be regarded as C₆-C₃-C₆ compounds, in which each C₆ moiety is a benzene ring, the variation in the state of oxidation of the connecting C₃ moiety determining the properties and class of each such compound.

Flavonoid compounds usually occur in plants as glycosides in which one or more of the phenolic hydroxyl groups are combines with sugar residues. The hydroxyl groups are nearly always found in positions 5 and 7 in ring A, while B ring commonly carries hydroxyl or alkoxyl groups at the 4’ position, or at 4’-position, or at both 3’-and 4’-positions. Glycosides of flavonoid compounds may bear the sugar on any of the available hydroxyl groups.

Table 5: FLAVONOIDS from Annonaceae plants:

FIG: Structural of flavonoids isolated from Annonaceae

 Taxonomy of Annonaceae:

On the basis of morphology and habit Annonaceae is a very homogenous plant family .They are trees or shurbs, sometimes climbing, usually evergreen, with resin canals septate pith in the stems. The leaves are alternate, entire and exsipulate.

 The leaves are simple, alternate, lack stipules, and generally are distichously arranged in flat sprays. The flowers are bisexual and the fragrant flowers frequently open before all parts are fully developed. The elongated floral axis also bears many helically disposed stamens and several to many simple pistils. All of the floral parts are distinct. The stamens are very short, consisting of the fertile central anther portion, a distal pad of fleshy connective tissue, and a short fleshy basal portion. The stamens are generally so tightly packed on the receptacle that often only the fleshy connective tissue of each is exposed. The pistils each have a superior ovary with one locule and 1-many parietal ovules. Sectioned seeds reveal channels or partitions in the ruminate endosperm. The pistils generally remain distinct and develop into berry-like fruits but sometimes they coalesce into multiple fruits like the custard apple.

  Information about :

undulate-margined narrow lanceolate leaves, axillary solitary flowers, and an etaerio of distintc and separate berries, grows wild as well as planted throughout the country. It is most commonly used as an ornamental street tree due to its effectiveness in combating noise pollution.

 Leaves:

Each leaf is a foot long, having 3-7 pairs of wavy-edged leaflets. Young leaves are dropping, coppery, limp and remain pendent even after attaining full maturity. The leaves grow alternately on the branches. Fresh leaves are a coppery brown color and are soft and delicate to touch; as the leaves grow older the color becomes a light green and finally a dark green.

 Flowers: The flowers are star-shaped, yellowish-green in colors, inconspicuous borne on long slender stalks, appearing from February to April.

 Fruits: The fruiting season is July and the fruits are egg-shaped. Fruit are borne in clusters of 10-20. Initially green but turning purple or black when ripe. These are loved by bats including the flying foxes.

 Uses: Bark possesses antibacterial and antifungal activities. (Hasan et al, 1989). It is used as febrifuge in treatment of fevers.

 Compounds isolated from the plant Polyalthia longifolia

Table 6:Compounds isolated from the plant Polyalthia longifolia

Biological Investigation Of P.longifolia

• Anti-inflammatory and cytotoxic diterpenes from formosan      P. longifolia var. pendula:

 Chang FR, Hwang TL, Yang YL, Li CE, Wu CC, Issa HH, Hsieh WB, Wu YC.

 Graduate Institute of Natural Products, Kaohsiung Medical University, Kaohsiung, Taiwan, ROC.

PMID: 17022008 [PubMed – indexed for MEDLINE]

• New antimicrobial alkaloids from the roots of P. longifolia var. pendula.

Faizi S, Khan RA, Azher S, Khan SA, Tauseef S, Ahmad A.

H.E.J. Research Institute of Chemistry, International Center for Chemical Sciences, University of Karachi, Karachi, Pakistan. [email protected]

PMID: 12709903 [PubMed – indexed for MEDLINE]

• Hypotensive activity and toxicology of constituents from root bark of P. longifolia var. pendula.

Saleem R, Ahmed M, Ahmed SI, Azeem M, Khan RA, Rasool N, Saleem H, Noor F, Faizi S.

Dr. HMI Institute of Pharmacology and Herbal Sciences, Hamdard University, Karachi-74600, Pakistan. [email protected]

PMID: 16261519 [PubMed – indexed for MEDLINE]

·    Cytotoxic constituents of P. longifolia var. pendula.

Chen CY, Chang FR, Shih YC, Hsieh TJ, Chia YC, Tseng HY, Chen HC, Chen SJ, Hsu MC, Wu YC.

Graduate Institute of Natural Products, Kaohsiung Medical University, Kaohsiung 807, Taiwan

PMID: 11087586 [PubMed – indexed for MEDLINE]

 Cytotoxic clerodane diterpenes from P. longifolia

Phadnis et al.,1988; Chakrabarty & Nath 1992; Hara et al.,1995; Hasan et al.,1995b; Rashid et al.,1996