Development of Siphonochilus aethiopicus as a treatment for colds and influenza and gas chromatographic analysis of volatiles of an insect repellent

Abstract

Part A of the study focuses on Siphonochilus aethiopicus, also known as African ginger, to determine its antiviral properties and the compounds responsible for the biological activity. African ginger is one of the most well-known medicinal plants in South Africa and is traditionally used to treat asthma, colds, coughs, flu, influenza, headaches and malaria. The biological properties of the plant have been extensively researched, however limited studies are reported on its antiviral activity and the compounds that contribute to this biological activity. Various compounds have been isolated from the plant, the most common being the sesquiterpenoid, siphonochilone, which is reported as the major compound of the plant, and its structurally similar compounds identified as lactones. The aim of this study was to prepare and identify a suitable extract, evaluate extracts for their antiviral properties against the influenza virus. Chapter 2 describes the different methods and conditions of extraction to quantitatively and qualitatively obtain the most suitable extracts. Fresh rhizomes, freshly dried ground rhizomes and five-year-old dried ground rhizomes were extracted with different polarities of solvents and analysed using GC-MS. It was concluded that the five-year-old dried ground rhizomes were the most suitable plant material to use for extraction since it contained the targeted compound, siphonochilone. Different purification methods were used for the extracts of the five-year-old dried ground rhizomes for the isolation of the targeted compounds which is described in Chapter 3. In this chapter an automated SPE, liquid handler and HPLC was used to successfully isolate and purify adequate quantities of the lactone and was confirmed using NMR. Siphonochilone crystallized out during steam distillation, and its structure confirmed by NMR. The isolated compounds along with the essential oil and ethanol extract were used for biological evaluation for antiviral properties against the influenza virus which is described in Chapter 4. The results suggested that the pure compound, siphonochilone showed significant inhibition against an Influenza virus, at

concentrations equivalent to the positive control, ribavirin. These results would suggest that siphonochilone could serve as possible natural antiviral drug. Part B of the study focuses on the analysis of a natural insect repellent and the longevity of the active ingredients during diffusion. Chapter 5 discusses the analysis of Noot-a-Bug, sweet orange oil blended with a naturally sourced enzyme cocktail, as a possible natural insect repellent. GC-MS analysis was performed to confirm the conversion of nootkatone from valencene in the sweet orange oil. HS-SPME-GC-MS was used to analyse the continuous diffusion of Noot-a-Bug and confirm the presence of nootkatone in the vaporised sample over a period of 24-h in a controlled environment.