Ournal of Pplied Cience and Nvironmental Anagement

The effect of polymer concentrations on some of the physicochemical properties of Vernonia amygdalina (Linn) and Garcinia kola (Heckel) extracts loaded microspheres was evaluated. Microspheres of the aqueous extracts was prepared by emulsion solvent evaporation using polyethylene glycol (PEG) mixtures of molecular weight 4000 and 6000 at different ratios of 1:0, 0:1, 1:1, 1:2 and 2:1 while the amounts of the extracts incorporated was constant for all ratios. The microspheres were evaluated for their particles sizes, yield, flavonoid content, loading efficiency, moisture loss and flow properties. In-vitro release studies were carried out by monitoring flavonoid release rate from the microspheres. The microspheres were spherical and uniformly shaped and exhibited good flow characteristics. Their size range, yield, loading efficiency, moisture loss and flavonoid content were 76 83 μm, 49 76 %, 47 82 %, 2.18 4.60 % and 17.10 23.80 mg%, respectively for V. amygdalina and 144 160 μm, 50 68 %, 51 68 %, 3.00 4.41 % and 20.00 28.70 mg%, respectively for G. kola. Flavonoids release from the microsphere was up to 90 % within 1 h and it followed a matrix release kinetic model with a super case-II transport mechanism. The concentrations of the polymers affected the yield, loading efficiency, moisture loss and the extent of flavonoid release of the microspheres but had no effect on their particle sizes and flavonoid content. These results may find useful application in the delivery of V. amygdalina and G. kola extracts since the combination of PEG of different molecular weights resulted in microspheres with good physicochemical and release properties. © JASEM http://dx.doi.org/10.4314/jasem.v19i1.4 Introduction Vernonia amygdalina is an edible plant of the Asteraceae family. It is commonly known as bitter leaf in Nigeria where the shrub grows up to three meters high. It grows in tropical African regions as well as in South Africa (Afolayan, et al., 2006). V. amygdalina has been reported to be effective against amoebic dysentery; gastrointestinal disorders; hepatotoxicities and diabetes mellitus (Izevbigie, 2003). The reported bioactive compound of V. amygdalina are saponins, alkaloids, terpenes, steroids, coumarines, flavonoids, phenolic acids, lignans, xanthones and anthraquinones (Cimanga, et al., 2004), edotides (Izevbigie, 2003), tannis (Harborne, 1973) and sesquiterpene lactone (Kupchan, et al., 1969). These compounds have been shown to be responsible for the observed biological activities. For example, the antiplasmodial (antimalarial) activity of its extracts has been related to the presence of flavonoids, saponins and alkaloids. Some studies have associated coumarines and flavonoids in most plant with anti-tumor activities in human (Monroe, et al., 1988). Sesquiterpene lactone and edotides present in the plant extract are believed to be responsible for the ability of the extract to fight cancer (Izevbigie, 2003; Kupchan, et al., 1969). Garcinia kola Heckel (Guttifera) is a dicotyledonous plant found in moist forest and grows as a medium sized tree up to about 12 m high. The seeds have a bitter taste hence the plant is commonly called bitter kola in Nigeria. The seeds have been consumed as a stimulant (Atawodi, et al., 1995). The seeds have been used in the treatment of liver disorders, and diarrhoea (Iwu, et al., 1990). G. kola has been reported to possess some hepatoprotective and aphrodisiac properties (Akintonwa and Essien, 1990; Ajibola and Satake, 1992). The plant has been referred to as a “wonder plant” because every part of it has been found to be of medicinal importance (Dalziel, 1937). Despite the many studies on the extracts of V. amygdalina and G. kola, only a few have attempted to formulate the extract into conventional dosage Some Physical Properties of Vernonia amygdalina 30 * 1 ERAGA, SO.; ARHEWOH, MI.; IVUONGBE, FE; EZE, HO forms (tablets, capsules, suspensions etc.), much less the more advanced delivery systems. PEGylation can be described as the molecular attachment of polyethylene glycols (PEGs) of different molecular weights to active drug molecules or surface treatment of drug-bearing particles with PEGs. It is a promising strategy of improving the pharmacokinetic behaviour of therapeutic drugs. The main pharmacokinetic outcomes of PEGylation are summarized as changes occurring in overall circulation life-span, tissue distribution pattern, and elimination pathway of the parent drug/particle (Abuchowski, et al., 1977; Fee, 2003). In this study, an attempt is made into formulating the extracts of V. amygdalina and G. kola into microspheres using high molecular weight polyethylene glycols and to evaluate the effects of polymer concentration on the physicochemical properties and drug release profiles of the microspheres. MATERIALS AND METHODS Materials: Polyethylene glycol (4000 and 6000), Tween 80 and quercetin were purchased from SigmaAldrich, Germany. Acetone and n-hexane (BDH Chemicals, England). Aluminium chloride (JHD Chemicals, China), Fehlings solution A and B and Dragendorffs reagent were obtained from our laboratory stock. All other chemicals used were of reagent grade and were used without further purification. Vernonia amygdalina leaves and seeds of Garcinia kola were bought from a local market in Benin City, Edo State, Nigeria and identified by Mr. Sunday Nweke of the Department of Pharmacognosy, University of Benin, Nigeria. Extraction processes: Pesticide free fresh V. amygdalina leaves were air dried for 7 days and milled into powders. Six hundred grams of the powder was soaked in 4 litres of distilled water overnight at room temperature. The mixture was filtered through a clean white gauze to remove the particulate matter before filtration through a filter paper. The resulting extract was concentrated to dryness in vacuum oven at 40 oC. The seeds of G. kola were peeled to remove the outer covering, cut into pieces and air dried over a period of 10 days. The seeds were ground into fine powder and 1.5 kg of the powdered seeds was soaked in distilled water for 24 hours with continuous stirring every two hours to facilitate penetration of solvent into the powders. The mixture was filtered to obtain the extract and concentrated to dryness in vacuum oven at 40 oC. Phytochemical analysis: The following tests were performed on the aqueous extracts of the dried, seeds. Test for starch was performed by means of iodine. Million’s reagent was used to test for proteins while the test for alkaloids was performed using Wagner and Dragendorff’s reagents. Other tests included Fehling’s solution for glycosides, ferric chloride test for tannins and the presence of flavonoids was detected using ammonium hydroxide solution. Microsphere preparation: The microspheres were prepared by emulsion solvent evaporation technique using the formula shown in Table 1. For batch A, five hundred milligram each of polyethylene glycol 4000 and 6000 were dissolved in 10 ml of water. Five hundred milligram of the extract was added to the PEG solution. The solution was poured into a 250 ml beaker containing 100 ml of liquid paraffin and 2 ml of Tween 80 as an emulsifying agent. The system was stirred (Silverson, UK) continuously for about 6 h at 500 rpm over a hot water bath maintained at 60 oC until the aqueous phase was completely removed by evaporation. The liquid paraffin was decanted and the collected microspheres were washed three times with 50 ml aliquots of n-hexane and acetone, filtered, air dried and kept in an air tight container at room temperature until evaluation. Percentage yield: The percentage yield was calculated using the formula in Eqn 1, where WM is the weight of the microspheres recovered from each batch and WT is the total weight of extract and polymer(s) used in the preparation (Sengel, et al., 2006).