Introduction

The use of plants in traditional medical practice has a long drawn history, and remains the mainstay of primary health care in most of the third world (Prescott-Allen and Prescott-Allen, 1982). Traditional medicines are used by about 60% of the world population; in both developing and developed countries (where modern medicines are predominantly used)

(Mythilypriya et al., 2007). Medicinal plants are believed to be an important source of new chemical substances with potential therapeutic benefits (Farnsworth, 1989; Eisner, 1990).

Garcinia kola (Heckel), an angiospermae, belonging to the family Guttiferae, is known in commerce as bitter cola. It is a plant found in the West African sub region, from Sierra Leone to Southern Nigeria, mostly in moist conditions

On chewing, G. kola seed has a bitter astringent and resinous taste, somewhat resembling that of raw coffee, followed by a slight sweetness. Bitter cola is a highly valued ingredient in African ethnomedicine because of its varied and numerous uses which are social and medicinal; thus making the plant an essential ingredient in folk medicine.

The relevance of a plant to pharmacy lies in the ability of the plant to elaborate organic compounds that possess pharmacological properties, or compounds that are of use in pharmaceutical formulations as flavouring agents or formulation aids. For example, some plant secondary metabolites such as alkaloids, phenols, tannins, glycosides, terpenoids, saponins, flavonoids and steroids have been implicated in their ability to inhibit the formation of pro-inflammatory signalling molecules such as prostaglandin or leukotrienes (Polya, 2003).

Recently discovered substances that have analgesic properties included those of the alkaloids, flavonoids and terpenoids phytochemical classes (Musa et al, 2008)

Constituents of the seed of G. kola include 1-3, 8-11 benzophenones, Garcinia biflavonones (GB-1, GB-2) and kolaflavonone (Cotterih et al., 1978). Apigenin based flavonoids represent 60% of the total flavonoids present in the diethyl ether fraction of G. kola seeds (Iwu and Igboko, 1982).

G. kola seeds contains a wide spectrum of organic compounds such as flavonoids which confer on it some anti-microbial and anti fungal actions against gram negative and gram positive microorganisms (Bohn, 1968). The biological activities of flavonoids include action against allergies, inflammation, free radicals, hepatoxins (Terashima et al., 2002).

The anti-inflammatory property of flavonoids is believed to result from inhibition of cyclo-oxygenase enzyme (Liang et al., 1999).

Earlier Harley (1970) had reported the antitusive, antitumour and aphrodisiac activities of G. kola while the flavonoids extracted from the seeds have been effective in the treatment of capillary fragility, retinal hemorrhage in hypertension, diabetic retinopathy, purpura, rheumatic arthritis, radiation disease, habitual abortion, frostbite, anaphylactic shock, experimental cancer and in the prevention of chromodacroyorrhoea produced by dietary and environmental stress (Elekwa, 1985). Despite these various uses, and most times, over long time periods, little toxicological information is available regarding safety following repeated exposure to Garcinia kola.

Furthermore, In Nigeria as in other developing countries, traditional medicines are in widespread use; with the practitioners formulating and dispensing the recipes.

The medicaments are prepared most often from a combination of two or more plant products which many a time may contain active constituents with multiple physiological activities and could be used in treating various disease conditions (Pieme et al., 2006; Ogbonnia et al, 2008). They are administered in most disease conditions over a long period of time without a proper dosage monitoring and consideration of toxic effects that might result from such a prolonged use. The warning regarding the potential toxicity of these therapies means that the practitioners should be kept abreast of the toxicity associated with the ingestion of medicinal herbs (Tédong et al., 2007).

In this study, the stem bark of G. kola was assessed for its phytochemical constitution and acute toxicity, in order to establish a baseline data for further research on this very important medicinal plant.

Materials And Methods

Preparation of Plant Material

Phytochemical Screening

Test for cardiac glycosides

Test for Anthraquinones

LD Determination

Assessment of Haematological Parameters

Result

Phytochemical Analysis

Phytochemical evaluation of the methanolic extract of Garcinia kola revealed the presence of tannins, phlobatannins, alkaloids, glycosides and flavonoids as shown in the table below:

Figure 1

Table 1 Phytochemical profile of Garcinia kola stem bark

LD₅₀ Determination

Figure 2

Table 2: Arithmetic Method of Karber

Figure 3

Table 3: Arithmetic Method of Reed and Muench

Assessment Of Some Hematological Parameters

Treatment, by gavages with Garcinia kola stem extract produced dose dependent changes in hematological parameters (Hb, PCV and RBC) in rats. Treated rats showed significant (p<0.001) dose dependent decrease in haemoglobin (Hb) concentration, packed cell volume (PCV) red blood cell (RBC) count in the first week and a significant reversal (increase) in the second week.

Figure 4

Table 4: Mean values of HB-Conc, PCV and RBC-count for the first 7 days of treatment with stem extract

Figure 5

Table 5: Mean values of HB-Conc, PCV and RBC-count for 14 days of treatment with stem extract

Discussion

The phytochemistry and median lethal dose (LD₅₀) _{of the methanolic extract of the stem bark of Garcinia kola (bitter cola) was investigated in this study.}

Decoction and infusion of Garcinia cola (Heckel) stem bark is used by traditional medicine practitioners in Ogoni, Nigeria, to treat dysmenorrhea.

The result of the phytochemical screening indicated that the stem bark of G. kola collected from the various locations, is very rich in tannins and phlobatannins, has a good flavonoid, cardiac glycoside and alkaloid content and is devoid of saponins and anthraquinones (Table 1), this finding contrast with the work of Monago & Akhidue (2002) who reported about the phytochemistry of the seed of G.kola. In their report, the seed of G. kola has a low tannin content and high saponin content. This difference may be explained by the fact that there could be variation in the occurrence of bioactive compounds in different part of the same plant or even in the same plant parts in plants found in different environments (Elujoba, 1989)

The stem bark of G. kola is used by traditional healers in the Ogoni area of Southern Nigeria to treat dysmenorrhea and burns, among other traditional uses. The phytochemical compounds, flavonoids and tannins, has been severally fingered as anti-inflammatory and analgesic active principles in medicinal plants (Liang et al., 1999; Terashima et al., 2002; Polya, 2003; Musa et al, 2008), the presence of these compounds in the extract may therefore suggest them to be the therapeutic principle behind the traditional antinoceptive use of the stem bark. Furthermore, the work of Bope et al, 1948 described the safety and effectiveness of phlobatannins and tannins in the local treatment of burns.

The high phlobatannin & tannin content of the extract therefore scientifically justify the use of pulverized G. kola stem bark to treat burns by the Ogoni people.

G. kola is a potential source of useful drugs. The seed of the plant has been reported to have antihepatotoxic (Braide, 1991; Akintowa and Essien, 1990), hypoglycemic (Iwu et al., 1990; Odeigah et al., 1999), aphrodisiac (Ajibola and Satake, 1992) and antioxidant (Olatunde et al., 2004) properties, among others. The stem bark has not been well researched, but from this phytochemical analysis, there is so much promising value that this part of the plant has.

The haematological studies showed that the indices examined (Hb, PCV, RBC and Platelet counts) showed a dose dependent significant reduction for the animal groups tested in the first week, and a dramatic dose-dependent rise in those tested for two weeks. This could be due to complexes which flavonoid forms with reactive metals such as iron, zinc and copper thereby reducing their nutrient absorption in the first week (Siegenberg, 1991). The formation of these complexes might have affected haemoglobin synthesis and erythropoiesis (Fairbanks, et al 1971, Esomonu et al, 2005). The physiological compensation for the reduced haemoglobin synthesis and erythropoiesis is by iron salvage as ageing erythrocytes are destroyed and the iron transported to the erythroid cells of the marrow and reutilized for new heamoglobin synthesis (Conley, 1974). This was seen in the second week as the values increased significantly.

Furthermore, the antioxidant activity of flavonoids (contained in G.kola stem bark powder) which ultimately maintains the haeme iron in its ferrous state (vis-à-vis the ferric state that is associated with production of defective methaemoglobin) seem to enhance erythropoiesis. The link between antioxidant activity and haemoglobin quality and quantity was shown by the observation that ascorbic acid (a standard antioxidant) via its action as a free radical scavenger, increased significantly the haemoglobin levels in children suffering from sickle cell anaemia (Jaja et al., 2002; Ahumibe and Braide, 2009).

In conclusion, the constituent of the methanol extract of G. kola stem bark extract do not impart any significant toxicological implication to erythrocytes, rather it showed the tendency of increasing the erythrocyte number over time, this property has been confirmed by Esomonu et al, 2005, in the seed of G.kola.

It has been argued that even if LD₅₀ values could be measured exactly and reproducibly, the knowledge of its precise numerical value would barely be of practical importance, because an extrapolation from the experimental animals to man is hardly possible (Lorke, 1983), however, it still serve a great purpose as a first pointer to the safety or toxic potential of a substance whose toxicity profile is not yet known.

The part of the plant under investigation (stem bark of G. kola) has an LD₅₀ value of 348mg/kg from the result above (Table 2 and 3). This value rates it as a very toxic substance (Gosselin et al, 1984). Though the effects on the red blood cells may be beneficial over a longer time, there should still be caution in the amount of the decoction of this stem bark which traditional healers need to expose their patients to.

Conclusion

The result in this study validate the traditional medicinal use of the evaluated part of G. kola in treating gynaecological pains (especially dysmenorrhoea) and wounds from burns; but the acute toxicity result also indicate that the plant part (stem bark) has a “very toxic” profile. This calls for caution in the “dose” of the decoction given to patients in traditional medical practice. Furthermore, the results of histopathological studies, that are ongoing, will throw further light on the organs of the body that are likely to be compromised in case of toxicity.

Acknowledgements