ISOLATION AND CHARACTERIZATION OF BIOACTIVE COMPOUNDS FROM STEMBARK EXTRACT OF Uapaca pilosa Hutch
Uapaca pilosa(Hutch.) a plant used in some parts of Africa in the treatment ofdysentery, menstrual pain, fever, constipation, erectile dysfunction, skin infections, female sterility, pile, rheumatism, emetic, tooth-troubles and fatigue. The dried plant was extracted, the extract was subjected tophytochemical investigation using standard method revealed the presence of alkaloids, flavonoids, anthraquinones, tannins, saponins, steroids, terpenoids and glycocides. Extensive silica gel column chromatography of the ethylacetate fraction of the stem bark extract, the most active of all the fractions, led to the isolation of two compounds GF1 and GF2. Their identities were determined by analysis of their spectral data using FTIR, 1D and 2D NMR. The structures of the compounds were supported by comparing their spectral data with the literature. GF1 was found to be betulin while GF2 was found to be beta-sitosterol. The antimicrobial screening of the crude extract and fractions using agar well diffusion methodshowed activity against Staphylococcus aureus, Shigella dysenteriae, Salmonella typhii, Bacillus subtilisand Escherichia coli. The Zone of Inhibition of theplant extract against selected microorganisms ranges from 13mm to 17mm against
Staphylococcus aureus, 10mm to 14mm against Bacillus subtilis, 12mm to 15mmagainst Shigella dysenteriae,15mm to 18mm against Escherichia coliand 10mm to 11mm againstSalmonella typhii. The MIC and MBC for the extract, fractions and isolated compounds were also determined. The range of Minimum Inhibitory concentration is between 6.25 mg/mL to 25 mg/mL for Staphylococcus aureus, 25 mg/mL for Shigella dysenteriae, 6.25 mg/mL for Bacillus subtilisand 12.50 mg/mL for
Escherichia coli while the Minimum Bactericidal Concentration range between 12.50mg/mL for Staphylococcus aureus, 50 mg/mL for Shigella dysenteriae, 12.50 mg/mL for Bacillus subtilis and 25 mg/mL for Escherichia coli. This study on the stem bark
extract from Uapaca pilosa, used traditionally in some parts of Africa as a medicinal plant for the treatment of various ailments has confirmed that it has antimicrobial activity against the microbes that cause some of these diseases.
Over the years the world traditional medicine has been known to take its source from higher plants and their extracts in the treatment of diseases and infections (Sofowora, 1983). Until 19th century, when the development of chemistry and synthetic organic chemistry started, medicinal plants were the sources of active materials used in healing and curing human diseases. Before the advent of modern methods of producing drugs, medicinal plants such as Allium sativum, Azadirchata indica and Citrus limonum were used in treating both malaria and typhoid fever. Also some plant leaves were used in treating skin rashes and to heal wounds. Likewise, modern pharmaceuticals rely heavily on these medicinal plants for their raw materials such as cocoa leaves and opium plant from papaver species for analgesics. The active principles of plants differ from one plant to another due to the diversity in biological activities (Sofowora, 1983; Kubmarawa et al., 2007; Krishnaiah et al., 2009).
Traditional medicinal practice has been established for centuries in many parts of the world. Numerous plants and herbs are used globally by traditional medicine practitioners. The practice is known to vary from one country to another (Sofowora, 1984). Extracts from the various plant parts (leaves, stem bark and roots) of various higher plants are used in herbal medicine production (Sofowora, 1983, 1984, 1993). Plants` extracts are given singly or as concoctions for the treatment of various ailments. In actual sense more than 75% of the world population depend on these various forms of concoctions and herbal decoctions for the treatment of infections (Robenson and Zhang, 2011).