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University of Namibia (2017)

Phytochemical analysis, radical scavenging and anti-microbial activity of the leaves of Gomphocarpus fruticosus

Maguraushe, Kadzashe Arnold

Titre : Phytochemical analysis, radical scavenging and anti-microbial activity of the leaves of Gomphocarpus fruticosus

Auteur : Maguraushe, Kadzashe Arnold

Université de soutenance  : University of Namibia

Grade : Master of Science in Industrial Biochemistry 2017

Résumé
Gomphocarpus fruticosus is a wild plant that belongs to the Asclepiadaceae family and has many traditional uses. The plant has demonstrated by this study a significant level of microbial and phytochemical activity ; the drug-resistant strains of microbes which have emerged in the last decade will be eradicated by the compounds this indigenous plant carries. This particular study aimed to scientifically validate the traditional uses of the plant G. fruticosus. The objectives of this study were (a) to extract and screen the phytochemicals in the leaves of G. fruticosus, (b) to quantify the detected phytochemicals, (c) to evaluate the anti-microbial activity of the leaf extracts and (d) to determine the antioxidant activity. The plant samples that were used in this research study were collected in Windhoek, Khomas Region of Namibia and in particular the areas surrounding the University of Namibia. Phytochemical screening was done followed by the evaluation of total flavonoid, phenol and tannin content using aluminium chloride method, folin-ciocalteu method and the potassium ferrocyanide methods respectively. Antimicrobial screening as well as MIC determination was done using the disk diffusion method. The antioxidant activity was determined using the DPPH Free Radical Scavenging Method. The quantitative phytochemical determinations were performed in triplicate and expressed as means (± standard deviation) and of the phytochemicals that were quantified, tannins were present in large amounts with 6.937±0.115 mg TA/g in the methanolic extract and 5.356±0.185 mg TA/g in the ethanolic extract. The MIC values for antimicrobial analysis were recorded as the least concentration of plant extracts that completely inhibited the growth of the microorganism. The MIC value for the ethanolic extract on Staphylococcus aureus was 1 mg/ml and for Escherichia coli it was 6 mg/ml. For DPPH, the extract with the lowest IC₅₀ was the one with the highest scavenging activity. The standard used was Vitamin C and it had an IC₅₀ value of 0.37 mg/ml. The IC₅₀ value of the methanolic extract and ethanolic extract were 0.25 mg/ml and 0.34 mg/ml respectively. At an overall point of perspective, it can be concluded that the leaf extract of G. fruticosus is of great medicinal significance due to the phytochemicals present, antimicrobial activity and antioxidant activity that was exhibited.

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