Evaluation of the anti-asthmatic property of Asystasia gangetica leaf extracts

https://doi.org/10.1016/S0378-8741(03)00227-7Get rights and content

Abstract

The leaf of Asystasia gangetica T. Adams (Acanthaceae) is used in many parts of Nigeria for the management of asthma. This study was aimed at investigating the anti-asthmatic property of hexane, ethylacetate, and methanol extracts of the leaves of Asystasia gangetica, obtained by successive sohxlet extraction. The results indicated that the extracts did not exhibit contractile or relaxant activity in isolated tissue preparations; however, they inhibited the contraction evoked by spasmogens; the IC50 were calculated, where possible. The extracts relaxed histamine-precontracted tracheal strips in the following degree of potency—ethylacetate extract>hexane extract=methanol extract. The extracts also exhibited anti-inflammatory activity in the order of magnitude—methanol extract>hexane extract>ethylacetate extract. Acute toxicity test estimated an i.p. LD50 of 2150 mg/kg in mice for methanol extract while phytochemical screening showed the presence of carbohydrates, proteins, alkaloids, tannins, steroidal aglycones, saponins, flavonoids, reducing sugars, and triterpenoids, with the methanol extract having the highest number of constituents. The study justified the use of the leaf of Asystasia gangetica in the management of asthma in Nigerian folk medicine.

Introduction

Asthma is a chronic disease of the airways/respiratory system with a worldwide incidence of 155 million (Cokson, 1999), and it is a disease that does not respect the boundaries of race, age, and gender. The availability of effective medications notwithstanding, the prevalence of asthma is increasing (Rona et al., 1995, Cokson, 1999) with 5–10% rate reported for Nigeria (Chukwu et al., 2000). There are incresing demand for the use of traditional medicines in the management of asthma, and Asystasia gangetica (L) T. Adams (Family Acanthaceae) is one of such plants with acclaimed potency in asthma.

Asystasia gangetica is a straggling herb usually found among short grasses and along pathways. The leaves are green, oval-shaped with rounded base, very slightly saw-edged, and smooth (Saunders, 1958). The plant is recognized as a potential food source because the leaves have been shown to contain high amounts of proteins, amino acids, minerals, sugars, lipids, and fiber (Yeoh and Wong, 1993).

In the traditional medicine of East Africa (Kenya), Asystasia gangetica is used as an anthelmintic. The leaves are crushed, boiled in water, and the decoction drunk as a cure for intestinal worms (Kokwaro, 1976). In Nigeria, the leaves of Asystasia gangetica are claimed to be highly effective in the local treatment of asthma (personal communication, 2000). The fresh leaves are macerated in local gin for 24 h or expressed and the extract drunk.

Over 70% of Nigeria’s more than 100 million people live in rural areas where traditional medicine practice is well established and patronized. The success of the practice has continued to reveal the potential of plants as therapeutic agents. As part of our continued efforts to screen Nigerian herbal remedies for pharmacological activity (Akah et al., 1997, Okoli and Akah, 2000, Nwafor et al., 2002), and in consideration of the claimed efficacy of Asystasia gangetica in native therapy of asthma, we investigated the leaves for anti-asthmatic activity.

Section snippets

Collection and preparation of plant material

Fresh leaves of Asystasia gangetica were collected in June 2000 at Orba, Enugu State, Nigeria. They were authenticated by Mr. A. Ozioko of the Department of Botany, University of Nigeria, Nsukka. A specimen of the plant (no. P02611) was deposited at the University’s Herbarium.

The collected leaves were sun-dried in open air for 7 days and reduced to coarse powder using a mortar and pestle.

Extraction of plant material

About 500 g of the dried powder was successively extracted with n-hexane, ethylacetate, and methanol using a

Guinea pig trachea

Guinea pigs of either sex (250–500 g), starved overnight but allowed free access to water, were used. The animals were killed by a blow on the head and exsanguinated. The trachea was dissected out and cut along its length on the dorsal surface. Incomplete transverse cuts were made along the segments of the cartilage to produce a zig-zag strip. The isolated trachea was mounted in a 30 ml organ bath containing Tyrode solution, maintained at 37±1 °C and gassed with air. The tissue was equilibrated

Results

Results of the toxicological studies established an i.p. LD50 of 2150 mg/kg for the methanol extract. Phytochemical analysis indicated the presence of several bioactive constituents as shown in Table 1. Solvent removal afforded percentage extractive yield of 1.14, 1.19, and 6.84% for hexane, ethylacetate, and methanol extracts, respectively.

Discussion

The extracts inhibited trachea contractions induced by histamine, serotonin, and acetylcholine. These agents are implicated in various ways in the pathogenesis of asthma. Histamine is the most implicated mediator in bronchconstriction that accompany asthma (Summers et al., 1981). Although the role of 5-HT in asthma is uncertain, it is a potent bronchoconstrictor (Barnes et al., 1998) and also increases acetylcholine release from airway nerves via 5-HT3 receptors (Takahashi et al., 1995).

References (31)

  • Bosin, T.R., 1978. Serotonin metabolism. In: Essman, W.B. (Ed.), Availability, Localization and Disposition, Vol. 1....
  • C. Chukwu et al.

    Efficacy and safety of zafirlukast (Acolate) in the management of patients with mild-to-moderate asthma

    West African Journal of Medicine

    (2000)
  • W. Cokson

    Alliance of genes and environment in asthma and allergy

    Nature

    (1999)
  • L.J. Dupont et al.

    Epinastine (WAL 801CL) modulates the noncholinergic contraction in guinea-pig airways in vitro by a prejunctional 5-HT1-like receptor

    European Respiratory Journal

    (1995)
  • T.W. Evans et al.

    Regional and time-dependent effects of airway inflammatory mediators in microvascular permeability in the guinea pig

    Clinical Science

    (1989)
  • Cited by (0)

    View full text