Physiological mechanisms underlying the use of Garcinia Kola Heckel in the treatment of asthma

Introduction Historically, plants have provided a source of inspiration for novel drug compounds, as plant-derived medicines have made large contributions to human health and well-being. Their role is two-fold in the development of new drugs: (1) they may become the basis for the development of new medicine, i.e. a natural blueprint for the development of new drugs; or (2) a phytomedicine to be used for the treatment of disease. Though there is availability of various orthodox drugs for the treatment of respiratory tract diseases in Nigeria, there is increasing interest in herbal remedies.1 The seeds of Garcinia kola (GK) form a major part of the herbal preparation used in traditional African medicine practice for the treatment of various respiratory tract diseases, including asthma.2 Garcinia kola Heckel belongs to the family Guttiferae, and it is commonly called bitter kola. In Nigeria, the plant is valued because of its edible nuts. The plant exhibits very potent pharmacological activities such as anti-oxidant, anti-bacterial, anti-viral, anti-fungal and anti-inflammatory properties.3–7 The anti-oxidant property of GK is attributed to its very high content of ascorbic acid.8 Phytochemistry of GK has shown its contents to include benzophenones, xanthones, biflavonoids, alkaloids, phenols, tannins, and saponins.8–15 Asthma is characterised by episodic or chronic wheezing, cough, and feeling of tightness in the chest as a result of bronchoconstriction.16 The fundamental cause is still unknown despite intensive research. However, three abnormalities are present: airway obstruction that is at least partially reversible, airway inflammation, and airway hyper-responsiveness to a variety of stimuli. A link to allergy has long been recognised, and plasma immunoglobulin E (IgE) levels are often elevated.17 Because of the importance of GK as a herb commonly used in herbal medicine for the treatment of asthma, it becomes necessary to determine the physiological mechanism(s) underlying its use. This paper reviews the function(s) of its phytochemical contents and how they are beneficial in the treatment of asthma. Garcinia kola Garcinia kola Heckel ‘bitter kola’ is popular in southern Nigeria. The plant is extensively used in herbal medicine and as food. It is usually found in the tropical rain forest region of West Africa. It prevails as a multi-purpose tree crop in the home gardens of southern Nigeria.18 The tree is usually cultivated within villages in southern Nigeria. It grows to a height of about 12–14 m and produces reddish, yellowish, or orange-coloured fruit.8,19 Each fruit contains two to four yellow seeds and a sour tasting pulp. The seeds when chewed have a bitter, astringent taste. The flowering of the plant occurs between December and January while the fruits mature between June and August. Garcinia kola is highly valued for medicinal use.20,21 The seeds are chewed as an aphrodisiac or used to cure cough, dysentery, or chest colds in herbal medicine.22 This plant has been referred to as a ‘wonder plant’ because every part of it has been found to be of medicinal importance.23 GK could serve as a raw material for pharmaceutical industries.24 GK is used in folklore remedies for the treatment of ailments such as liver disorders, hepatitis, diarrhoea, laryngitis, bronchitis, and gonorrhoea.7,25 The seed is used to prevent and relieve colic; it can also be used to treat headache.26 The plant can be used in the treatment of stomach ache and gastritis.27 Iwu7 reported the use of this plant for the treatment of jaundice, high fever, and as purgative. Administration of GK seed extract caused an increase in testosterone production in Sprague–Dawley rats which is thought to be due to its anti-oxidant properties.28,29 Also, Adesanya et al19 confirmed the spermatogenic and tissue enhancing effect of GK extract in male Wistar rats. David et al30 showed that GK extract exhibits a dilatory effect on the alveolar ducts, alveolar sacs, and alveoli thereby improving respiratory activities; in Swiss albino mice this may be due to its anti-oxidant properties. GK has been shown to inhibit smooth muscle activity. It relaxes the smooth muscles of the uterus and the intestine.31 Although GK lacks caffeine,32 its alkaloid and biflavonoids fractions are said to relax the smooth muscles.31 GK has a bronchodilatory effect.33,34