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A concise synthesis of (−)-steviamine is reported along with the synthesis of its analogues 10-nor-steviamine, 10-nor-ent-steviamine and 5-epi-ent-steviamine. These compounds were tested against twelve glycosidases (at 143 μg mL−1 concentrations) and were found to have in general poor inhibitory activity against most enzymes. The 10-nor analogues however, showed 50-54% inhibition of α-L-rhamnosidase from Penicillium decumbens while one of these, 10-nor-steviamine, showed 51% inhibition of N-acetyl-β-D-glucosaminidase (from Jack bean) at the same concentration (760 μM). A concise synthesis of steviamine is reported along with the synthesis of its analogues 10-nor-steviamine, 10-nor-ent-steviamine and 5-epi-ent-steviamine. These compounds were tested against twelve glycosidases (at 143 g/mL concentrations) and were found to have in general poor inhibitory activity against most enzymes. The 10-nor analogues however, showed 50-54% inhibition of -L-rhamnosidase from Penicillium decumbens while one of these, 10-nor-steviamine, showed 51% inhibition of N-acetyl--D-glucosaminidase (from Jack bean) at the same concentration (760 M).

The chemical constituents of the essential oil from the leaves of Gynura divaricata (L.) DC.were investigated by GC-FID and GC-MS. Seventeen compounds, representing 97.1 % of the chromatographical fraction of the oil, were detected. The major constituents, cubenol (65.7 %) and spathulenol (6.4 %), were isolated using column chromatography and identified by NMR and MS analysis. The antioxidant, cytotoxicity and antimicrobial activities of the essential oil, the hexane, dichloromethane and methanol extracts of G. divaricata leaves were investigated. The essential oil and the crude extracts showed antioxidant activity using the ABTS and DPPH methods, respectively. The essential oil exhibited significant cytotoxicity against KB, MCF-7 and NCI-H187 cancer cell lines with the IC 50 values of 5.79, 47.44 and 17.65 μg/mL, respectively and had a MIC of 50 μg/mL against Mycobacterium tuberculosis H 37 Ra. Cubenol had an IC 50 value of 45.37 μg/mL against the NCI-H187 cancer cell line. All extracts were non-cytotoxic against Vero cells. The essential oil and the extracts showed antimicrobial activity using the disc diffusion assay. The methanol extract was the most potent of the three extracts.