Abstract
Among all the major infectious diseases, bacterial respiratory tract infections are the major cause of infant death. Traditional medicine is viewed as a valuable resource and plays a crucial role as an alternative in primary healthcare systems in developing countries. However, most have not been investigated for their safety and efficacy. Therefore, this study aimed to document medicinal plants traditionally used to treat respiratory tract infections in southern Africa and use a comprehensive list to document these plants to see if they have been evaluated for biological activities. In addition, the study intended to assess the phytochemicals and qualities of a variety of plants using GC-MS to identify and quantify secondary metabolites. The antimicrobial activity of plants was assessed using minimum inhibitory concentration. The anti-inflammatory effects of various plant species were assessed using bovine serum albumin using diclofenac as a standard.
Ethnobotany studies using traditional knowledge as a selection strategy have given priority to specific plants that can be targeted for isolation and identification of new bioactive compounds. An ethnomedicinal review was done to identify forty-nine plants that were reported to be used to treat respiratory infections. Moreover, only six plants were selected based on their potential to treat respiratory tract infections in southern Africa. Four solvents (butanol, ethanol, methanol and water) were used for extraction in this study because of their wide polarity range. Extraction was done using the Soxhlet apparatus. A total of 24 plant extracts were evaluated for their antimicrobial activity and 72 for anti-inflammatory activity.
The aim of the present investigation was to analyse the bioactive compounds (secondary metabolites) from selected plants of the family Asteraceae. Phytochemical screening was carried out using Gas Chromatography-Mass Spectrometry (GC-MS) to detect and identify various compounds from the selected plant species. The phytochemical investigation of the medicinal plants, Arctotis arctotoides (L.f) O.Hoffm., Brachylaena discolor DC., Bidens pilosa L., Dicoma anomala Sond., Helichrysum crispum D.Don., and Senecio asperulus DC., led to the detection of compounds such as the presence of 2,4-Di-tert-butylphenol, 9,12,15- Octadecatrienoic acid, methyl ester, (Z, Z, Z); 9,12-Hexadecadienoic acid, methyl ester; Dibutyl phthalate; Hexadecane; Pentadecane; Phenol; Phytol; Tridecanoic acid, methyl ester,
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and vitamin E as the main compounds in the majority of the plant samples. The identified compounds play a very big role in their biological activities.
Antimicrobial activity was assessed using one method, namely minimum inhibitory concentrations (MIC). The MICs were determined using three Gram-negative bacteria namely, Klebsiella aerogenes, Klebsiella pnuemonaie, and Veillonella parvula and one Gram-positive bacteria Staphylococcus aureus. All species investigated exhibited moderate to low antimicrobial activity against at least one of the bacterial strains. Indicating several compounds contributing to the promising activity of the plant extracts.
The bovine serum assay (BSA) was used to assess the inhibition of protein denaturation for anti-inflammatory activity of the selected species. All the species exhibited good activity with exception of most of the water samples. Twenty-one extracts inhibited protein denaturation while fifteen extracts inhibited at the lowest concentration of 50 ug/ml. In addition, the selected plants, i.e A. arctotoides, B. discolor, B. pilosa, D. anomala, H. crispum and S. asperulus showed exceptional inhibition and others inhibited the enzyme moderately, showing that while these chemicals contribute to the activity of extracts, they are not responsible for any considerable activity on their own.
The results obtained from investigating the chemical constituents and biological activity of the selected plant species used to treat respiratory tract infections; provide preliminary information towards the validation of the traditional use of some of these plants. There is some correlation between the chemical compounds present and biological activity. The results provide a basis for further studies to isolate and identify the active compounds in the plant species and evaluate the possible synergism amongst the isolated compounds.