Browsing by Author "Asiamah, Isaac"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Chemical Composition, Antioxidant, and Antimicrobial Activities of the Leaf and Fruit Essential Oils of the West African Plum, Vitex doniana
    (Journal of Chemistry, 2023) Odoom, Jahnissi Frimpomah; Aboagye, Caleb Impraim; Acheampong, Philipina; Asiamah, Isaac; Darko, Godfred; Borquaye, Lawrence Sheringham; 0000-0001-7157-646X
    Vitex doniana (West African plum or black plum) is a plant with varying phytoconstituents and biological activities across different countries. In this study, essential oils extracted from the leaves and fruits of Vitex doniana cultivated in Ghana were investigated for their antimicrobial and antioxidant activities. -e antioxidant actions of the essential oils were determined using hydrogen peroxide (H2O2), phosphomolybdenum, thiobarbituric acid reactive substances (TBARS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. For both essential oils, the total antioxidant capacities ranged from 44 to 68 µg/g AAE, the IC50 values for H2O2 scavenging activity were between 87 and 242 µg/mL, whereas that for DPPH assay were between 322 and 599 µg/mL. -e IC50 for the TBARS assay for both essential oils also ranged from 247 to 414 µg/mL. -e antimicrobial activities of the essential oils were investigated using the broth dilution assay. -e minimum inhibition concentration for the essential oils ranged from 12.5 to 50 mg/mL. BioClm inhibitory activity was also evaluated for both essential oils, and the fruit essential oil showed a half-maximal inhibition of bioClm formation (BIC50) at 44.40±0.6 mg/mL, whereas the BIC50 value of the leaf essential oil was 109.1±0.9 mg/mL. -e fruit essential oil was superior to the leaf essential oil in inhibiting the secretion of pyoverdine. Molecular docking analyses suggested that methyl cinnamate, ethyl cinnamate, p-menth-4-en-3-one, trans-α-ionone, benzyl benzoate, isobutyl cinnamate, and folic acid likely interacted with LasR and algC proteins, and hence, contributed to the inhibition of bioClm formation and pyoverdine secretion. Essential oils from Vitex doniana could, therefore, be exploited as a natural source of radical scavenging and antimicrobial agents and could be useful in the pharmaceutical, food, and cosmetic industries.
  • Thumbnail Image
    Item
    Value addition and determination of 5-hydroxytryptophan (5-HTP) in seeds of Griffonia simplicifolia
    (2003-11-28) Asiamah, Isaac
    The aromatic amino acid. 5-1-lydroxytryptophan (5-HTP) is naturally present in seeds of Griffonia simplicifolia. a West African medicinal plant found principally in Ghana. Ivory Coast and Togo. The overwhelming advantages it has over synthetic anti-depressants and tryptophan in alleviating the numerous effects o serotonin deficiency syndrome such as anxiety, depression, insomnia, and migraine headaches among others have attracted the commercialization of Griffonia simplicifolia seeds. However effective commercialization of the seeds requires quality control checks in order to be sure that the active drug substance, 5-HTP is present at high levels and stable in the harvested seeds. In this research work the 5-1ITP content in the seeds of Griffonia simplicifolia was determined by using HPLC. Using an ODS column with dimension of 4.6mm x 25cm. a mobile phase of 3% methanol in 0.005M NaH2PO4 buffer (pH 4.8), a flow rate of I .5ml/min and UV detector at 275nm, 5-HTP eluted at an average retention time (Rt) of 6.60mm. This is important for quick assays of bulk batches of samples for quality control checks and export purposes. The levels of 5-HTP in Griffonia simplicifolia seeds collected from various locations a Ghana were found to be between 14.1 8 - I 8.24%w/w of seed weight when freshly harvested. The level of 5-HTP in harvested seeds of Griffonia simplicifolia was found to decrease at a rate of 4.62%w/w per month of storage under tropical atmospheric conditions. However, stability studies showed that refrigeration could not preserve 5-HTP in seeds. Cold storage was found to decrease the content of 5-HTP at an average rate of 6.77%w/w per month. On the other hand, it was found that heating seeds at 60°C for 30mm is enough to inactivate enzymes and hence preserve 5-HTP in Griffonia simplicifolia seeds. The average rate of fall in 5-HTP content was l.79%\w/w per month.