university of kwazulu-natal faculty of science and agriculture school ...

There have been only four biological studies on Plectranthus hadiensis where the
antiplasmodial, insect-antifeedant, antifungal, antiradical and antibacterial properties of
this plant extract and the isolated compounds were evaluated for activity (van Zyl et al.,
2008; Laing et al., 2006; Mothana et al., 2008; Wellsow et al., 2006). The acetone
extract of this plant was found to be inactive as an insect-antifeedant (Wellsow et al.,
2006). The hexane extract showed good activity against Sclerotinia sclerotiorum,
Rhizoctonia solani and an unknown Candida species while the dichloromethane extract
showed moderate activity against bacterial strains, B. subtilis and X. campestris and the
fungal microorganism, Sclerotinia sclerotiorum as well as an unknown Candida species
(Laing et al., 2006).
Three royleanones 33, 36 and 38 were isolated previously from the dichloromethane
extract of the aerial parts of P. hadienis (van Zyl et al., 2008) and the isomers of 33 and
36, 34 and 37 respectively, were isolated from the ethanol extract of Coleus zeylanicus (a
synonym for P. hadiensis) (Mehrotra et al., 1989). Compounds 33 and 36 exhibited
anticancer activity against breast, lung, renal, melanoma and central nervous system cell
lines (MCF-7, NCI-H460, TK-10, UACC-62 and SF-268, respectively) with both
compounds proving to be less potent than the positive control, Cyclosporin A (Cerqueira
et al., 2004; Gaspar-Marques et al., 2002). These three compounds (33, 36 and 38) have
also proven to be active against six strains of methicillin resistant Staphylococcus aureus,
two strains of vancomycin-resistant Enterococcus faecalis, Bacillus subtilis, Vibrio
cholera and Xanthomonas campestris (Laing et al., 2006; Teixera et al., 1997; Gaspar-
Marques et al., 2006). Compounds 36 and 38 (van Zyl et al., 2008) exhibited
antimalarial activity with 38 displaying synergistic properties when combined with
quinine (Tables 11 and 13 on pages 72 and 76, respectively). There were no reports of
biological activity in compounds 34 and 37.
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