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Effect of some abiotic factors on the concentration of β-sitosterol of Prunus Africana (Hook.f.) Kalkman in the tropical forests of Cameroon

Maurice Tchouakionie, Emmanuel Youmbi, Michel Ndoumbe Nkeng, Siméon Fogue Kouam, Marc Lamshôft, and Michael Spiteller, from the different institute of the Cameroon and Germany. wrote a research article about, Impact of Abiotic Factors on β-sitosterol in Prunus Africana in Cameroon. entitled, Effect of some abiotic factors on the concentration of β-sitosterol of Prunus Africana (Hook.f.) Kalkman in the tropical forests of Cameroon. This research paper published by the International Journal of Agronomy and Agricultural Research (IJAAR). an open access scholarly research journal on Agronomy. under the affiliation of the International Network For Natural Sciences | NNSpub. an open access multidisciplinary research journal publisher.

Abstract

Prunus africana is a medicinal plant which develops in the mountains of several African countries. β-sitosterol can be used as a marker for the control of the product quality of the aforementioned plant in terms of phytotherapy. Farmers and public authorities do not have information on the influence of altitude and chemical characteristics of soils on the concentration of β-sitosterol of P. africana. To contribute to solve the problem, this research, carried out in Cameroon, aims to appreciate the effect of abiotic factors on the above phenotypic character. In nine composite samples of barks taken at different altitudes, the concentration of β-sitosterol is appreciated via qualitative analyses by Thin Layer Chromatography, High Performance Liquid Chromatography and quantitative analyses by Gas Chromatography coupled with the Mass Spectrometry. The chemical analyses of soils taken under the stems of the aforementioned trees were made. The statistics were carried out using the SAS software. The concentration of β-sitosterol in each population of P. africana varies from zero to 38.65 µg/ml. There is variability between the averages of the aforementioned concentration with respect to altitude and chemical elements of the soils but the differences are not significant. The Ascending Hierarchical Clustering distributes populations into three groups. These tools obtained are indispensable for the ground management, the products exploited from this tree species and the production of seeds for creating forest and agro-forest plantations.

Introduction

Prunus africana (Hook. F.) Kalkman is a medicinal plant which develops in the forests of mountains at altitudes going from 700 m to more than 1000 m in several countries of Africa (Avery et al., 2001). Its bark is exploited and marketed internationally because of its effectiveness in the treatment of benign prostates and hyperplasia (Watt and Bryer, 1962, Bankill, 1997, cit. by Hall et al., 2000).

In pecuniary terms of value, one Kilogram of rough bark is bought at 300 F CFA from farmers and the drawn extract from the aforesaid Kilogram costs 500 000 F. CFA in pharmaceutical industries (Vockins, 2000, cit. Avana et al., 2006).

P. africana is a component of biodiversity which represents 6 % of the species used for forest and agro-forest plantations in the agro-ecological zone of the high plateaus of the West of Cameroon (Tchouakionie et al, 2010).

To optimize the output of the plantations, it is necessary to take into account the biotic and abiotic factors relating to the P. africana. The small farmers and public authorities do not have formal information on the variability of the concentration of β-sitosterol, the principal active matter of P. africana with respect to altitude and the chemical characteristics of the soils of the aforementioned species plantations.

The general objective of this study is to appreciate the effect of some abiotic factors on the concentration of β-sitosterol of P. africana within mount Cameroon and the Bamenda high land areas. To achieve this goal, three specific objectives were formulated:

To evaluate the effect of altitude on the concentration of β-sitosterol of P. africana; to appreciate the correlation between the chemical characteristics of the soils and the concentration of β-sitosterol of the aforementioned species; to group the populations of P. africana according to their concentration in β-sitosterol.

In the biological context, P. africana belongs to the family of Rosaceae and are found practically only on mountains (Letouzey, 1982).The detailed description of the adult tree is materialized by characteristic phytogenetic parts (fig. 1).

The stem (Fig.1.A) is a seed-bearer in an agro-ecosystem in Akum, within Mezam Division, in the North-West of Cameroon. The base of trunk presents a simple footing of 8-10 cm (Fig.1. B). The young seedlings are visible under this tree. These seedlings come from two modes of pollination in particular: self-fertilization and cross-pollinated parents. Pollination here is primarily entomophilous. However the implication of certain birds was noted (Avana, 2006). Flowering is irregular in P. africana and occurs every 2 to 3 years. Fructification intervenes 2 to 3 months after the beginning of flowering. The number of fruits per inflorescence varies from 1 to 6 units (Fig. 1.C).

The natural ecological zone of P. africana in Cameroon is confined to the mountain and sub-mountain forests of altitudes ranging between 1500-3000 m (Vivien and Faure, 2011). The surface distribution of the forests of P. africana planted from 1976 to 2007, reached 625 ha with at least 1.526.430 trees (Kadu et al., 2012). The peasants partly receive seeds from non-governmental organizations and official establishments.

Concerning the influence of biotic factors on the development of P. africana, analyses carried out by Dawson and Powell (1999) using molecular markers indicated that the variation is quite effective at the level of the genes (fig. 2).

There are quantitative and qualitative differences in chemical compounds from the barks of P. africana within geographically dispersed populations (Hall et al., 2000). The concentration of β-sitosterol, the major component of the bark of P. africana, varies from 101 to 150 μg/ml between origins and 50 to 191μg/ml between individuals (Simons and Leakey, 2004, cit. Avana, 2006). One of the factors of the environment which has an influence on the behavior of the plant is the physico-chemical composition of the soils (Sant' Anna, 1980).

Sudberg (2005) established that β-sitosterol is the most significant sterol chemical compound which exists in the extract of P. africana. It can be used as a marker for the control of the quality of barks of this species. Kadu et al., (2012) established that most chemical components of the bark of P. africana are correlated between themselves. Environmental parameters such as temperature, precipitation and the altitude of the sites are not correlated with the concentration of the aforesaid components. The metabolic chart of β-sitosterol (Anonym, 2013) shows that its empirical formula is C29H50 O and developed: In a natural environment, plants are nourished, from organic matter transformed beforehand into minerals by the organisms present in the soils (Larouche, 1983). These soils minerals influence the aspect of some phonotypic characters of the trees within its ecosystem.

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