Isolation and characterization of β-sitosterol, oleanolic, 19- dehyroursolic and yarumic acids, from Plectranthus esculentus leaves and tubers

Plectranthus esculentus N.E.Br. (family Lamiaceae) also known as Livingstone potato (vat or rizga in Nigeria), is a dicotyledonous perennial shrub growing up to 2 m tall. While it is cultivated mainly for its edible tubers, the plant is potentially valuable as phytomedicine. Three varieties (vat-long’at, vat-riyom and vat-bebot) are well known among the Berom of Plateau State, Nigeria. The vat-bebot variety (which showed good promise in bioactivity studies) was used in this study. The leaves and tubers were extracted successively with hexane, ethyl acetate, methanol and water. Fractionation of the active ethyl acetate extracts was carried out using open column and preparative High Performance Liquid Chromatography (prep HPLC). This led to the isolation of β-sitosterol and oleanolic acid from the leaves; while 19-dehydroursolic acid and yarumic acid, as well as β-sitosterol were isolated from the tubers. Nuclear Magnetic Resonance (NMR) and Electron Impact Mass Spectroscopy (EIMS) were used to characterize isolated compounds. Comparing acquired spectral data of isolated compounds with those from literature helped to confirm the identity of the compounds. The isolation and characterisation of these compounds, from Plecthranthus esculentus, have not been hitherto reported in literature

Brine shrimp toxicity of acidic fractions of Boswellia dalzielii gum resin

Boswellia dalzielii is the West African species of the frankincense producing genus ( B. carterii, B. frereana and B. serrata are the more popular congeners). Its ethnobotanical uses include the treatment of rheumatism, venereal diseases and gastro-intestinal disorders, swellings/ growths on the skin, among other things. The anti-inflammatory, anti-hyperlipidemic and immunomodulatory activities of B. serrata gum resin have been established as being due to triterpenoic (boswellic) acid derivatives such as b-boswellic acid, 3–O-acetyl–b–boswellic acid, 11–keto-b-boswellic acid and 3–O-acetyl–11-keto-b-boswellic acid. It was therefore considered pertinent to study the cytotoxic activity of the acidic fraction of B. dalzielii gum resin. The gum resin of B. dalzielii was extracted with diethyl ether and partitioned into acidic and neutral/basic fractions. These fractions had earlier been shown to have significant anti-inflammatory activity. The acidic fraction was fractionated into four sub-fractions (A-D) using Accelerated Gradient Chromatography (AGC). The fractions and sub-fractions, when tested for brine shrimp lethality, showed very high activity (LC5050µg/mL). Also the acidic fraction had a significantly higher activity over the neutral fraction. Being the most active, sub-fraction D (LC50 = 0.0013µg/mL) was subjected to AGC on silica. This afforded two pure compounds which, from preliminary chemical tests, were shown to be triterpenoids. Journal of Pharmacy & Bioresources Vol. 2(2) 2005: 137-14

Isolation and characterization of incensole from Boswellia dalzielii stem bark

Boswellia dalzielii is the West African species of the frankincense genus. It is used in ethnomedicine to treat gastrointestinal disorders, rheumatism and various diseases of microbial origin. The dried pulverized bark material was extracted with 50% ethanol by percolation. Column chromatography, gel filtration and preparative thin-layer chromatography (TLC) of the ethyl acetate fraction yielded incensole, a cembrane diterpenoid. Its structure was established by nuclear magnetic resonance (NMR) spectroscopy, including 2-D NMR experiments (reported here for the first time), and fast atom bombardment mass spectrometry (FAB-MS). Tests for antimicrobial and antioxidant (free-radical scavenging) activities revealed that while the extracts and fractions demonstrated strong antioxidant and antimicrobial activities, incensole was only moderately active. Key Words: Boswellia dalzielii; Incensole; Diterpenoid; Antimicrobial activity; Antioxidant activity; Journal of Pharmacy and Bioresources Vol.1(1) 2004: 7-1