South African Journal of Science
On-line version ISSN 1996-7489
Print version ISSN 0038-2353
VAN ZYL, R.L.; KHAN, F.; EDWARDS, T.J. and DREWES, S.E.. Antiplasmodial activities of some abietane diterpenes from the leaves of five Plectranthus species. S. Afr. j. sci. [online]. 2008, vol.104, n.1-2, pp.62-64. ISSN 1996-7489.
Seven known abietane diterpenes were isolated from five Plectranthus species, namely P. hadiensis, P. lucidus, P. ecklonii, P. purpuratus subsp. purpuratus and P. purpuratus subsp. tongaensis. The seven compounds were tested for their antiplasmodial activity and for their ability to inhibit β-haematin formation. Overall, they showed good activity (IC50 values ranging from 3.11 to 14.65 µM), with one compound being 62% as effective as chloroquine in inhibiting β-haematin formation. However, the cytotoxicity profile indicated a low degree of specificity towards the malaria parasite. When combined with quinine, three compounds interacted in an additive manner whereas one interacted synergistically.