Growth perfomance and phytochemical profiles of prunus africana sampled from Muguga, Kobujoi and Karuri, Kenya
Nyamai, Dorothy Wavinya
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Prunus africana (Hook.f.) is an evergreen tree that grows in African mountains. The species’ bark and bark extracts are used for the treatment of benign prostate hyperplasia. The pharmacological efficacy of the extracts is said to be due to synergistic effect of several compounds such as phytosterols, pentacyclic triterpenoids and ferulic acid esters. High demand for the bark and bark extracts has led to over-exploitation of natural population of the species. As a result, P. africana is listed as an endangered species in Appendix II of CITES. Conservation of the species can be done through domestication. However, management and growth factors need to be established first to ensure success of on-farm production. Therefore, the World Agroforestry Centre established a P. africana stand at Muguga, Kenya to monitor the species growth and performance. The main objective of the current study was to evaluate and compare growth characteristics and phytochemical profile of trees in the domesticated stand at Muguga, with reference samples from Kobujoi, a wild stand and Karuri a remnant on-farm stand. Extraction of compounds was done using aqueous, hexane, dichloromethane and methanol solvents. Phytochemical analysis was done using Liquid Chromatography and Gas Chromatography-mass spectrometry. Gas Chromatography-Mass Spectrometry data was analyzed using GC Chemstation software version 11. Height of trees in the domesticated stand at Muguga ranged from 3 meters to 14 meters and diameter at breast height from 0.9cm to 104.5cm. Out of the 273 trees in the plantation, 92 (33%) were fruiting at the time of data collection. Evaluation of the crude yields of organic extracts of the three populations showed no significance difference (p>0.05). From the three stands, bark sample essential oils were essentially composed of myristic acid, linoleic acid, lauric acid, methyl myristate, methyl laurate and methyl linoleate. These compounds lower cholesterol levels in prostates of BPH patients. Campesterol, β-sitosterol, lup-20(29)-en-3-one, palmitic acid, β-sitostenone, (3.β., 5.α)- stigmast-7-en-3-ol, stigmastan-3,5-diene and α-tocopherol were detected in dichloromethane and hexane extracts of the three populations. (3.β., 5.α)- stigmast-7-en-3-ol, β-sitosterol and β-sitostenone increase urine flow and inhibit prostaglandin production in the prostate. Cyanidin-o-galactoside, cyanidin-3-o-rutinoside, procyanidin B5 and robinetinidol-(4-α-8) catechin-(6,4-α)robinetinol are believed to inhibit cell proliferation and have free radical scavenging activity on cancerous cells. Ursolic acid is believed to have anti-inflammatory, antioxidant and anti-proliferative effects on BPH. Karuri population essential oils had significantly (p<0.05) higher amounts of myristic and lauric acids. Muguga population showed significant variation (p<0.05) on the concentration of myristic acid, linoleic acid, methyl myristate and α-tocopherol compared to Karuri and Kobujoi populations. The results demonstrate that domestication does not interfere significantly (p>0.05) with the phytochemical composition of P. africana and thus on-farm planting can be carried out. The morphological and phytochemical data has important implications in drawing strategies for sustainable harvesting, management and conservation of this species through cultivation.