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

Abstract
Three diterpenes of the abietane class, 7β-acetoxy-6β-hydroxyroyleanone (I), 6β,7β-
dihydroxyroyleanone (II) and ent-pimara-8(14),15-diene-3β,11α-diol (III) and three
triterpenes, 2α,3α,19α-trihydroxyurs-12-en-28-oic acid (IV), stigmasterol (V) and lupeol (VI)
were isolated from the stem and leaf material of Plectranthus hadiensis. The structures of the
compounds were elucidated using 2D NMR spectroscopy and Mass spectrometry. All six
compounds have been isolated previously, but this is the first occurrence of compounds III-VI
in Plectranthus hadiensis. This is also the first report of the isolation of a pimarene from
Plectranthus, which provides a biochemical link to other genera in the family Lamiaceae where
this class of compounds exist.
Compounds I to IV were tested for their antibacterial activity against Enterococcus faecalis and
Pseudomonas aeruginosa as well as their anticancer activity against breast (MCF-7), renal (TK-
10) and melanoma (UACC-62) cell lines. Compounds I and II exhibited good antibacterial
activity against Enterococcus faecalis and Pseudomonas aeruginosa and although the ent-
pimara-8(14),15-diene-3β,11α-diol (III), was inactive against E. faecalis, it was very active
against P. aeruginosa. Compound IV, the triterpenoid, was structurally different to I-III and
did not show any anti-bacterial activity. Compounds I-III were weakly active toward the
cancerous renal (TK-10), melanoma (UACC-62) and breast (MCF-7) cell lines, while IV was
inactive in all of the cell lines.
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