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

Chapter 5 Conclusion
The aim of this research project was to isolate and identify the compounds extracted from
Plectranthus hadiensis and to compare the phytochemistry with previous studies as well
as to test the compounds isolated for antibacterial and anticancer proprties.
According to literature (Abdel-Mogib et al., 2002), abietane diterpenes are the most
abundantly occurring compounds in the genus Plectranthus with there being two
instances where ten triterpenes (oleanolic acid, ursolic acid, betulin, β-sitosterol,
plectranthoic acid, plectranthoic acid A, plectranthoic acid B, acetylplectranthoic acid,
plectranthadiol and hexacosanol) have been isolated (Misra et al., 1971; Razdan et al.,
1982).
Compounds I and II have been isolated only once before (Mehrotra et al., 1989) from
Coleus zeylanicus which is a synonym for Plectranthus hadiensis. This is the first report
of compounds III to VI being isolated from P. hadiensis. Lupeol has never been isolated
in the Plectranthus genus, however an isopimarane (7α,18-dihydroxy-isopimara-
8(14),15-diene) was reported in Plectranthus diversus (Rasikari, 2007) and stigmasterol
has been isolated twice before, once from Coleus and once from Plectranthus.
Three of the six compounds isolated from P. hadiensis, (7β-acetoxy-6β-
hydroxyroyleanone (I), 7β,6β-dihydroxyroyleanone (II) and ent-pimara-8(14),15-diene-
3β,11α-diol (III)) were abietanes while the other three were common pentacyclic
triterpenes known as euscaphic acid (IV), stigmasterol (V) and lupeol (VI). These three
triterpenoids add to the ten previously isolated from the Plectranthus species. Even
though ethyl acetate and methanol were used as extraction solvents, nothing of interest
was isolated from these solvents. The relatively non-polar hexane extract yielded five of
the six compounds with euscaphic acid IV being isolated from the dichloromethane
extract. The isolation of triterpenoids in P. hadiensis is not surprising as most plant
species contain these common sterols.
156