Phytochemical and anti-drepanocytosis studies of Cajanus cajan, Callistemon viminalis, Melaleuca bracteata var. Revolution Gold and Syzygium guineense.

Abstract

All over Africa, traditional healers use medicinal plants to prepare medicines to treat a wide range of illnesses. One of these illnesses is sickle cell anaemia or drepanocytosis or sicklemia. This disease is particularly common among sub-Saharan Africans with a clear predominance in equatorial Africa. However, it also exists in North Africa, Greece, Turkey, Saudi Arabia and India. An estimated 50 million people are affected worldwide. A literature review on sickle cell anaemia revealed that a number of plants have anti-drepanocytosic activity. The availability and frequency of ethnobotanic use of plants were taken into account when selecting the plants investigated in this study. Cajanus cajan, Callistemon viminalis, Melaleuca bracteata var. Revolution Gold and Syzygium guineense (from DRC and South Africa) were selected for study. The selected plants were subjected to modern phytochemical analysis. A total of 8 compounds were isolated from the plants’ extracts and their structures determined by modern spectroscopic techniques (1D and 2D NMR, FT-IR and MS). S. guineense from DRC (Democratic Republic of Congo) yielded flavanonoid glycoside (A) as its major chemical constituent. The South African S. guineense afforded 4 compounds namely betulinic acid (B), sitosterol (C), friedelan-3-one (D) and a betulinic acid derivative (E). Cajanus cajan showed the presence of fatty acids, one of them was characterized as an unsaturated fatty acid (I). Callistemon viminalis afforded one compound, betulic acid (F) and Melaleuca bracteata afforded two compounds which were characterized as betulinic acid acetate (G) and ursolic acid acetate (H). CH3-(CH2)n-CH2-CH=CH-CH2-CH=CH-(CH2)n-CH2-CH2-COOH The investigation of the anti-drepanocytosis activities of the extractives and their crude extracts showed in vitro antisickling activity. Ethyl acetate crude extracts of Callistemon viminalis and Melaleuca bracteata; hexane, dichloromethane and ethyl acetate crude extracts of Syzygium guineense of DRC, betulinic acid, betulinic acid acetate and maslinic acid showed a high antisickling activity, more than 70% of normalization. The compound BF4, a fatty acid, from Melaleuca bracteata was found to have a medium activity, between 50 and 70% of normalization and oleanolic acid showed the weakest activity, between 10 and 50 % of normalization. Maslinic acid and oleanolic acid which were used for anti-sickling bioassay were isolated and characterized from Syzygium cordatum by my supervisor, Professor Shode. Others crude extracts and pure isolated compounds were found to be non-active antisickling agents. These included crude hexane and methanol extracts of Cajanus cajan; crude dichloromethane extract of Callistemon viminalis; crude dichloromethane, methanol and 80% aqueous methanol extracts of Melaleuca bracteata; crude hexane, dichloromethane, ethyl acetate, and methanol extracts of Syzygium guineense (South Africa); ursolic acid from Melaleuca bracteata and flavanone glycoside from Syzygium guineense of DRC. This is the first report of the in vitro anti-sickling activity of betunilic acid, betulinic acid acetate, oleanolic acid, and maslinic acid.